diff --git a/src/librustc/back/link.rs b/src/librustc/back/link.rs
index ee7fbed9e9f..8be8a433ef8 100644
--- a/src/librustc/back/link.rs
+++ b/src/librustc/back/link.rs
@@ -131,13 +131,13 @@ pub mod jit {
             for cratepath in r.iter() {
                 let path = cratepath.to_str();
 
-                debug!("linking: %s", path);
+                debug2!("linking: {}", path);
 
                 do path.with_c_str |buf_t| {
                     if !llvm::LLVMRustLoadCrate(manager, buf_t) {
                         llvm_err(sess, ~"Could not link");
                     }
-                    debug!("linked: %s", path);
+                    debug2!("linked: {}", path);
                 }
             }
 
@@ -303,7 +303,7 @@ pub mod write {
             for pass in sess.opts.custom_passes.iter() {
                 do pass.with_c_str |s| {
                     if !llvm::LLVMRustAddPass(mpm, s) {
-                        sess.warn(fmt!("Unknown pass %s, ignoring", *pass));
+                        sess.warn(format!("Unknown pass {}, ignoring", *pass));
                     }
                 }
             }
@@ -381,9 +381,9 @@ pub mod write {
         let prog = run::process_output(cc_prog, cc_args);
 
         if prog.status != 0 {
-            sess.err(fmt!("building with `%s` failed with code %d",
+            sess.err(format!("building with `{}` failed with code {}",
                         cc_prog, prog.status));
-            sess.note(fmt!("%s arguments: %s",
+            sess.note(format!("{} arguments: {}",
                         cc_prog, cc_args.connect(" ")));
             sess.note(str::from_utf8(prog.error + prog.output));
             sess.abort_if_errors();
@@ -554,7 +554,7 @@ pub fn build_link_meta(sess: Session,
                               dep_hashes: ~[@str],
                               pkg_id: Option<@str>) -> @str {
         fn len_and_str(s: &str) -> ~str {
-            fmt!("%u_%s", s.len(), s)
+            format!("{}_{}", s.len(), s)
         }
 
         fn len_and_str_lit(l: ast::lit) -> ~str {
@@ -599,7 +599,7 @@ pub fn build_link_meta(sess: Session,
 
     fn warn_missing(sess: Session, name: &str, default: &str) {
         if !*sess.building_library { return; }
-        sess.warn(fmt!("missing crate link meta `%s`, using `%s` as default",
+        sess.warn(format!("missing crate link meta `{}`, using `{}` as default",
                        name, default));
     }
 
@@ -612,7 +612,7 @@ pub fn build_link_meta(sess: Session,
                 // filestem that returned an @str
                 let name = session::expect(sess,
                                            output.filestem(),
-                                           || fmt!("output file name `%s` doesn't\
+                                           || format!("output file name `{}` doesn't\
                                                     appear to have a stem",
                                                    output.to_str())).to_managed();
                 if name.is_empty() {
@@ -762,7 +762,7 @@ pub fn mangle(sess: Session, ss: path,
 
     let push = |s: &str| {
         let sani = sanitize(s);
-        n.push_str(fmt!("%u%s", sani.len(), sani));
+        n.push_str(format!("{}{}", sani.len(), sani));
     };
 
     // First, connect each component with <len, name> pairs.
@@ -874,7 +874,7 @@ pub fn output_dll_filename(os: session::Os, lm: LinkMeta) -> ~str {
         session::OsAndroid => (android::DLL_PREFIX, android::DLL_SUFFIX),
         session::OsFreebsd => (freebsd::DLL_PREFIX, freebsd::DLL_SUFFIX),
     };
-    fmt!("%s%s-%s-%s%s", dll_prefix, lm.name, lm.extras_hash, lm.vers, dll_suffix)
+    format!("{}{}-{}-{}{}", dll_prefix, lm.name, lm.extras_hash, lm.vers, dll_suffix)
 }
 
 pub fn get_cc_prog(sess: Session) -> ~str {
@@ -890,7 +890,7 @@ pub fn get_cc_prog(sess: Session) -> ~str {
             session::OsAndroid =>
                 match &sess.opts.android_cross_path {
                     &Some(ref path) => {
-                        fmt!("%s/bin/arm-linux-androideabi-gcc", *path)
+                        format!("{}/bin/arm-linux-androideabi-gcc", *path)
                     }
                     &None => {
                         sess.fatal("need Android NDK path for linking \
@@ -915,29 +915,29 @@ pub fn link_binary(sess: Session,
 
     let output = if *sess.building_library {
         let long_libname = output_dll_filename(sess.targ_cfg.os, lm);
-        debug!("link_meta.name:  %s", lm.name);
-        debug!("long_libname: %s", long_libname);
-        debug!("out_filename: %s", out_filename.to_str());
-        debug!("dirname(out_filename): %s", out_filename.dir_path().to_str());
+        debug2!("link_meta.name:  {}", lm.name);
+        debug2!("long_libname: {}", long_libname);
+        debug2!("out_filename: {}", out_filename.to_str());
+        debug2!("dirname(out_filename): {}", out_filename.dir_path().to_str());
 
         out_filename.dir_path().push(long_libname)
     } else {
         out_filename.clone()
     };
 
-    debug!("output: %s", output.to_str());
+    debug2!("output: {}", output.to_str());
     let cc_args = link_args(sess, obj_filename, out_filename, lm);
-    debug!("%s link args: %s", cc_prog, cc_args.connect(" "));
+    debug2!("{} link args: {}", cc_prog, cc_args.connect(" "));
     if (sess.opts.debugging_opts & session::print_link_args) != 0 {
-        io::println(fmt!("%s link args: %s", cc_prog, cc_args.connect(" ")));
+        io::println(format!("{} link args: {}", cc_prog, cc_args.connect(" ")));
     }
 
     // We run 'cc' here
     let prog = run::process_output(cc_prog, cc_args);
     if 0 != prog.status {
-        sess.err(fmt!("linking with `%s` failed with code %d",
+        sess.err(format!("linking with `{}` failed with code {}",
                       cc_prog, prog.status));
-        sess.note(fmt!("%s arguments: %s",
+        sess.note(format!("{} arguments: {}",
                        cc_prog, cc_args.connect(" ")));
         sess.note(str::from_utf8(prog.error + prog.output));
         sess.abort_if_errors();
@@ -951,7 +951,7 @@ pub fn link_binary(sess: Session,
     // Remove the temporary object file if we aren't saving temps
     if !sess.opts.save_temps {
         if ! os::remove_file(obj_filename) {
-            sess.warn(fmt!("failed to delete object file `%s`",
+            sess.warn(format!("failed to delete object file `{}`",
                            obj_filename.to_str()));
         }
     }
diff --git a/src/librustc/back/rpath.rs b/src/librustc/back/rpath.rs
index fa111a01615..60289e0ebe5 100644
--- a/src/librustc/back/rpath.rs
+++ b/src/librustc/back/rpath.rs
@@ -29,7 +29,7 @@ pub fn get_rpath_flags(sess: session::Session, out_filename: &Path)
         return ~[];
     }
 
-    debug!("preparing the RPATH!");
+    debug2!("preparing the RPATH!");
 
     let sysroot = sess.filesearch.sysroot();
     let output = out_filename;
@@ -49,7 +49,7 @@ fn get_sysroot_absolute_rt_lib(sess: session::Session) -> Path {
 }
 
 pub fn rpaths_to_flags(rpaths: &[Path]) -> ~[~str] {
-    rpaths.iter().map(|rpath| fmt!("-Wl,-rpath,%s",rpath.to_str())).collect()
+    rpaths.iter().map(|rpath| format!("-Wl,-rpath,{}",rpath.to_str())).collect()
 }
 
 fn get_rpaths(os: session::Os,
@@ -57,13 +57,13 @@ fn get_rpaths(os: session::Os,
               output: &Path,
               libs: &[Path],
               target_triple: &str) -> ~[Path] {
-    debug!("sysroot: %s", sysroot.to_str());
-    debug!("output: %s", output.to_str());
-    debug!("libs:");
+    debug2!("sysroot: {}", sysroot.to_str());
+    debug2!("output: {}", output.to_str());
+    debug2!("libs:");
     for libpath in libs.iter() {
-        debug!("    %s", libpath.to_str());
+        debug2!("    {}", libpath.to_str());
     }
-    debug!("target_triple: %s", target_triple);
+    debug2!("target_triple: {}", target_triple);
 
     // Use relative paths to the libraries. Binaries can be moved
     // as long as they maintain the relative relationship to the
@@ -78,9 +78,9 @@ fn get_rpaths(os: session::Os,
     let fallback_rpaths = ~[get_install_prefix_rpath(target_triple)];
 
     fn log_rpaths(desc: &str, rpaths: &[Path]) {
-        debug!("%s rpaths:", desc);
+        debug2!("{} rpaths:", desc);
         for rpath in rpaths.iter() {
-            debug!("    %s", rpath.to_str());
+            debug2!("    {}", rpath.to_str());
         }
     }
 
@@ -172,7 +172,7 @@ mod test {
         let res = get_install_prefix_rpath("triple");
         let d = Path(env!("CFG_PREFIX"))
             .push_rel(&Path("lib/rustc/triple/lib"));
-        debug!("test_prefix_path: %s vs. %s",
+        debug2!("test_prefix_path: {} vs. {}",
                res.to_str(),
                d.to_str());
         assert!(res.to_str().ends_with(d.to_str()));
@@ -233,7 +233,7 @@ mod test {
     #[test]
     fn test_get_absolute_rpath() {
         let res = get_absolute_rpath(&Path("lib/libstd.so"));
-        debug!("test_get_absolute_rpath: %s vs. %s",
+        debug2!("test_get_absolute_rpath: {} vs. {}",
                res.to_str(),
                os::make_absolute(&Path("lib")).to_str());
 
diff --git a/src/librustc/driver/driver.rs b/src/librustc/driver/driver.rs
index 5fe1a5f7233..76f48577fe6 100644
--- a/src/librustc/driver/driver.rs
+++ b/src/librustc/driver/driver.rs
@@ -386,7 +386,7 @@ pub fn phase_6_link_output(sess: Session,
 
 pub fn stop_after_phase_3(sess: Session) -> bool {
    if sess.opts.no_trans {
-        debug!("invoked with --no-trans, returning early from compile_input");
+        debug2!("invoked with --no-trans, returning early from compile_input");
         return true;
     }
     return false;
@@ -394,7 +394,7 @@ pub fn stop_after_phase_3(sess: Session) -> bool {
 
 pub fn stop_after_phase_1(sess: Session) -> bool {
     if sess.opts.parse_only {
-        debug!("invoked with --parse-only, returning early from compile_input");
+        debug2!("invoked with --parse-only, returning early from compile_input");
         return true;
     }
     return false;
@@ -402,17 +402,17 @@ pub fn stop_after_phase_1(sess: Session) -> bool {
 
 pub fn stop_after_phase_5(sess: Session) -> bool {
     if sess.opts.output_type != link::output_type_exe {
-        debug!("not building executable, returning early from compile_input");
+        debug2!("not building executable, returning early from compile_input");
         return true;
     }
 
     if sess.opts.is_static && *sess.building_library {
-        debug!("building static library, returning early from compile_input");
+        debug2!("building static library, returning early from compile_input");
         return true;
     }
 
     if sess.opts.jit {
-        debug!("running JIT, returning early from compile_input");
+        debug2!("running JIT, returning early from compile_input");
         return true;
     }
     return false;
@@ -670,7 +670,7 @@ pub fn build_session_options(binary: @str,
             let lint_name = lint_name.replace("-", "_");
             match lint_dict.find_equiv(&lint_name) {
               None => {
-                early_error(demitter, fmt!("unknown %s flag: %s",
+                early_error(demitter, format!("unknown {} flag: {}",
                                            level_name, lint_name));
               }
               Some(lint) => {
@@ -690,7 +690,7 @@ pub fn build_session_options(binary: @str,
             if name == debug_flag { this_bit = bit; break; }
         }
         if this_bit == 0u {
-            early_error(demitter, fmt!("unknown debug flag: %s", *debug_flag))
+            early_error(demitter, format!("unknown debug flag: {}", *debug_flag))
         }
         debugging_opts |= this_bit;
     }
@@ -1033,7 +1033,7 @@ pub fn build_output_filenames(input: &input,
 
 pub fn early_error(emitter: @diagnostic::Emitter, msg: ~str) -> ! {
     emitter.emit(None, msg, diagnostic::fatal);
-    fail!();
+    fail2!();
 }
 
 pub fn list_metadata(sess: Session, path: &Path, out: @io::Writer) {
@@ -1058,7 +1058,7 @@ mod test {
         let matches =
             &match getopts([~"--test"], optgroups()) {
               Ok(m) => m,
-              Err(f) => fail!("test_switch_implies_cfg_test: %s", f.to_err_msg())
+              Err(f) => fail2!("test_switch_implies_cfg_test: {}", f.to_err_msg())
             };
         let sessopts = build_session_options(
             @"rustc",
@@ -1079,7 +1079,8 @@ mod test {
             &match getopts([~"--test", ~"--cfg=test"], optgroups()) {
               Ok(m) => m,
               Err(f) => {
-                fail!("test_switch_implies_cfg_test_unless_cfg_test: %s", f.to_err_msg());
+                fail2!("test_switch_implies_cfg_test_unless_cfg_test: {}",
+                       f.to_err_msg());
               }
             };
         let sessopts = build_session_options(
diff --git a/src/librustc/driver/session.rs b/src/librustc/driver/session.rs
index 19e866c70a3..5998f590a33 100644
--- a/src/librustc/driver/session.rs
+++ b/src/librustc/driver/session.rs
@@ -296,7 +296,7 @@ impl Session_ {
     // This exists to help with refactoring to eliminate impossible
     // cases later on
     pub fn impossible_case(&self, sp: Span, msg: &str) -> ! {
-        self.span_bug(sp, fmt!("Impossible case reached: %s", msg));
+        self.span_bug(sp, format!("Impossible case reached: {}", msg));
     }
     pub fn verbose(&self) -> bool { self.debugging_opt(verbose) }
     pub fn time_passes(&self) -> bool { self.debugging_opt(time_passes) }
diff --git a/src/librustc/front/test.rs b/src/librustc/front/test.rs
index 254116bd507..e4904863a94 100644
--- a/src/librustc/front/test.rs
+++ b/src/librustc/front/test.rs
@@ -78,7 +78,7 @@ impl fold::ast_fold for TestHarnessGenerator {
 
     fn fold_item(&self, i: @ast::item) -> Option<@ast::item> {
         self.cx.path.push(i.ident);
-        debug!("current path: %s",
+        debug2!("current path: {}",
                ast_util::path_name_i(self.cx.path.clone()));
 
         if is_test_fn(self.cx, i) || is_bench_fn(i) {
@@ -91,7 +91,7 @@ impl fold::ast_fold for TestHarnessGenerator {
                                      tests");
                 }
                 _ => {
-                    debug!("this is a test function");
+                    debug2!("this is a test function");
                     let test = Test {
                         span: i.span,
                         path: self.cx.path.clone(),
@@ -100,7 +100,7 @@ impl fold::ast_fold for TestHarnessGenerator {
                         should_fail: should_fail(i)
                     };
                     self.cx.testfns.push(test);
-                    // debug!("have %u test/bench functions",
+                    // debug2!("have {} test/bench functions",
                     //        cx.testfns.len());
                 }
             }
@@ -327,7 +327,7 @@ fn mk_test_module(cx: &TestCtxt) -> @ast::item {
         span: dummy_sp(),
      };
 
-    debug!("Synthetic test module:\n%s\n",
+    debug2!("Synthetic test module:\n{}\n",
            pprust::item_to_str(@item.clone(), cx.sess.intr()));
 
     return @item;
@@ -381,7 +381,7 @@ fn is_extra(crate: &ast::Crate) -> bool {
 }
 
 fn mk_test_descs(cx: &TestCtxt) -> @ast::Expr {
-    debug!("building test vector from %u tests", cx.testfns.len());
+    debug2!("building test vector from {} tests", cx.testfns.len());
     let mut descs = ~[];
     for test in cx.testfns.iter() {
         descs.push(mk_test_desc_and_fn_rec(cx, test));
@@ -404,7 +404,7 @@ fn mk_test_desc_and_fn_rec(cx: &TestCtxt, test: &Test) -> @ast::Expr {
     let span = test.span;
     let path = test.path.clone();
 
-    debug!("encoding %s", ast_util::path_name_i(path));
+    debug2!("encoding {}", ast_util::path_name_i(path));
 
     let name_lit: ast::lit =
         nospan(ast::lit_str(ast_util::path_name_i(path).to_managed()));
diff --git a/src/librustc/lib/llvm.rs b/src/librustc/lib/llvm.rs
index 49798288d40..0ef98d96568 100644
--- a/src/librustc/lib/llvm.rs
+++ b/src/librustc/lib/llvm.rs
@@ -2270,7 +2270,7 @@ impl TypeNames {
                 Metadata => ~"Metadata",
                 X86_MMX => ~"X86_MMAX",
                 Integer => {
-                    fmt!("i%d", llvm::LLVMGetIntTypeWidth(ty.to_ref()) as int)
+                    format!("i{}", llvm::LLVMGetIntTypeWidth(ty.to_ref()) as int)
                 }
                 Function => {
                     let out_ty = ty.return_type();
@@ -2278,25 +2278,25 @@ impl TypeNames {
                     let args =
                         args.map(|&ty| self.type_to_str_depth(ty, depth-1)).connect(", ");
                     let out_ty = self.type_to_str_depth(out_ty, depth-1);
-                    fmt!("fn(%s) -> %s", args, out_ty)
+                    format!("fn({}) -> {}", args, out_ty)
                 }
                 Struct => {
                     let tys = ty.field_types();
                     let tys = tys.map(|&ty| self.type_to_str_depth(ty, depth-1)).connect(", ");
-                    fmt!("{%s}", tys)
+                    format!("\\{{}\\}", tys)
                 }
                 Array => {
                     let el_ty = ty.element_type();
                     let el_ty = self.type_to_str_depth(el_ty, depth-1);
                     let len = ty.array_length();
-                    fmt!("[%s x %u]", el_ty, len)
+                    format!("[{} x {}]", el_ty, len)
                 }
                 Pointer => {
                     let el_ty = ty.element_type();
                     let el_ty = self.type_to_str_depth(el_ty, depth-1);
-                    fmt!("*%s", el_ty)
+                    format!("*{}", el_ty)
                 }
-                _ => fail!("Unknown Type Kind (%u)", kind as uint)
+                _ => fail2!("Unknown Type Kind ({})", kind as uint)
             }
         }
     }
@@ -2307,7 +2307,7 @@ impl TypeNames {
 
     pub fn types_to_str(&self, tys: &[Type]) -> ~str {
         let strs = tys.map(|t| self.type_to_str(*t));
-        fmt!("[%s]", strs.connect(","))
+        format!("[{}]", strs.connect(","))
     }
 
     pub fn val_to_str(&self, val: ValueRef) -> ~str {
diff --git a/src/librustc/metadata/creader.rs b/src/librustc/metadata/creader.rs
index 3b563e47426..c41e1d78f64 100644
--- a/src/librustc/metadata/creader.rs
+++ b/src/librustc/metadata/creader.rs
@@ -74,11 +74,11 @@ struct cache_entry {
 }
 
 fn dump_crates(crate_cache: &[cache_entry]) {
-    debug!("resolved crates:");
+    debug2!("resolved crates:");
     for entry in crate_cache.iter() {
-        debug!("cnum: %?", entry.cnum);
-        debug!("span: %?", entry.span);
-        debug!("hash: %?", entry.hash);
+        debug2!("cnum: {:?}", entry.cnum);
+        debug2!("span: {:?}", entry.span);
+        debug2!("hash: {:?}", entry.hash);
     }
 }
 
@@ -97,7 +97,7 @@ fn warn_if_multiple_versions(e: @mut Env,
 
         if matches.len() != 1u {
             diag.handler().warn(
-                fmt!("using multiple versions of crate `%s`", name));
+                format!("using multiple versions of crate `{}`", name));
             for match_ in matches.iter() {
                 diag.span_note(match_.span, "used here");
                 let attrs = ~[
@@ -154,7 +154,7 @@ fn visit_view_item(e: @mut Env, i: &ast::view_item) {
                   }
             }
           };
-          debug!("resolving extern mod stmt. ident: %?, meta: %?",
+          debug2!("resolving extern mod stmt. ident: {:?}, meta: {:?}",
                  ident, meta_items);
           let cnum = resolve_crate(e,
                                    ident,
@@ -317,7 +317,7 @@ fn resolve_crate(e: @mut Env,
 
 // Go through the crate metadata and load any crates that it references
 fn resolve_crate_deps(e: @mut Env, cdata: @~[u8]) -> cstore::cnum_map {
-    debug!("resolving deps of external crate");
+    debug2!("resolving deps of external crate");
     // The map from crate numbers in the crate we're resolving to local crate
     // numbers
     let mut cnum_map = HashMap::new();
@@ -326,18 +326,18 @@ fn resolve_crate_deps(e: @mut Env, cdata: @~[u8]) -> cstore::cnum_map {
         let extrn_cnum = dep.cnum;
         let cname_str = token::ident_to_str(&dep.name);
         let cmetas = metas_with(dep.vers, @"vers", ~[]);
-        debug!("resolving dep crate %s ver: %s hash: %s",
+        debug2!("resolving dep crate {} ver: {} hash: {}",
                cname_str, dep.vers, dep.hash);
         match existing_match(e,
                              metas_with_ident(cname_str, cmetas.clone()),
                              dep.hash) {
           Some(local_cnum) => {
-            debug!("already have it");
+            debug2!("already have it");
             // We've already seen this crate
             cnum_map.insert(extrn_cnum, local_cnum);
           }
           None => {
-            debug!("need to load it");
+            debug2!("need to load it");
             // This is a new one so we've got to load it
             // FIXME (#2404): Need better error reporting than just a bogus
             // span.
diff --git a/src/librustc/metadata/csearch.rs b/src/librustc/metadata/csearch.rs
index 841142ee62f..6def597b89f 100644
--- a/src/librustc/metadata/csearch.rs
+++ b/src/librustc/metadata/csearch.rs
@@ -210,17 +210,17 @@ pub fn get_field_type(tcx: ty::ctxt, class_id: ast::DefId,
     let cstore = tcx.cstore;
     let cdata = cstore::get_crate_data(cstore, class_id.crate);
     let all_items = reader::get_doc(reader::Doc(cdata.data), tag_items);
-    debug!("Looking up %?", class_id);
+    debug2!("Looking up {:?}", class_id);
     let class_doc = expect(tcx.diag,
                            decoder::maybe_find_item(class_id.node, all_items),
-                           || fmt!("get_field_type: class ID %? not found",
+                           || format!("get_field_type: class ID {:?} not found",
                                    class_id) );
-    debug!("looking up %? : %?", def, class_doc);
+    debug2!("looking up {:?} : {:?}", def, class_doc);
     let the_field = expect(tcx.diag,
         decoder::maybe_find_item(def.node, class_doc),
-        || fmt!("get_field_type: in class %?, field ID %? not found",
+        || format!("get_field_type: in class {:?}, field ID {:?} not found",
                  class_id, def) );
-    debug!("got field data %?", the_field);
+    debug2!("got field data {:?}", the_field);
     let ty = decoder::item_type(def, the_field, tcx, cdata);
     ty::ty_param_bounds_and_ty {
         generics: ty::Generics {type_param_defs: @~[],
diff --git a/src/librustc/metadata/cstore.rs b/src/librustc/metadata/cstore.rs
index a5f541412de..03af7c98b87 100644
--- a/src/librustc/metadata/cstore.rs
+++ b/src/librustc/metadata/cstore.rs
@@ -152,7 +152,7 @@ pub fn get_dep_hashes(cstore: &CStore) -> ~[@str] {
         let cdata = cstore::get_crate_data(cstore, cnum);
         let hash = decoder::get_crate_hash(cdata.data);
         let vers = decoder::get_crate_vers(cdata.data);
-        debug!("Add hash[%s]: %s %s", cdata.name, vers, hash);
+        debug2!("Add hash[{}]: {} {}", cdata.name, vers, hash);
         result.push(crate_hash {
             name: cdata.name,
             vers: vers,
@@ -164,9 +164,9 @@ pub fn get_dep_hashes(cstore: &CStore) -> ~[@str] {
         (a.name, a.vers, a.hash) <= (b.name, b.vers, b.hash)
     };
 
-    debug!("sorted:");
+    debug2!("sorted:");
     for x in sorted.iter() {
-        debug!("  hash[%s]: %s", x.name, x.hash);
+        debug2!("  hash[{}]: {}", x.name, x.hash);
     }
 
     sorted.map(|ch| ch.hash)
diff --git a/src/librustc/metadata/decoder.rs b/src/librustc/metadata/decoder.rs
index 69b3c79d1a9..5c6a7c4f3b7 100644
--- a/src/librustc/metadata/decoder.rs
+++ b/src/librustc/metadata/decoder.rs
@@ -89,7 +89,7 @@ pub fn maybe_find_item(item_id: int, items: ebml::Doc) -> Option<ebml::Doc> {
 
 fn find_item(item_id: int, items: ebml::Doc) -> ebml::Doc {
     match maybe_find_item(item_id, items) {
-       None => fail!("lookup_item: id not found: %d", item_id),
+       None => fail2!("lookup_item: id not found: {}", item_id),
        Some(d) => d
     }
 }
@@ -148,7 +148,7 @@ fn item_family(item: ebml::Doc) -> Family {
       'g' => PublicField,
       'j' => PrivateField,
       'N' => InheritedField,
-       c => fail!("unexpected family char: %c", c)
+       c => fail2!("unexpected family char: {}", c)
     }
 }
 
@@ -160,7 +160,7 @@ fn item_visibility(item: ebml::Doc) -> ast::visibility {
                 'y' => ast::public,
                 'n' => ast::private,
                 'i' => ast::inherited,
-                _ => fail!("unknown visibility character")
+                _ => fail2!("unknown visibility character")
             }
         }
     }
@@ -494,8 +494,8 @@ pub enum DefLike {
 pub fn def_like_to_def(def_like: DefLike) -> ast::Def {
     match def_like {
         DlDef(def) => return def,
-        DlImpl(*) => fail!("found impl in def_like_to_def"),
-        DlField => fail!("found field in def_like_to_def")
+        DlImpl(*) => fail2!("found impl in def_like_to_def"),
+        DlField => fail2!("found field in def_like_to_def")
     }
 }
 
@@ -550,14 +550,14 @@ impl<'self> EachItemContext<'self> {
         let def_like = item_to_def_like(doc, def_id, self.cdata.cnum);
         match def_like {
             DlDef(def) => {
-                debug!("(iterating over each item of a module) processing \
-                        `%s` (def %?)",
+                debug2!("(iterating over each item of a module) processing \
+                        `{}` (def {:?})",
                        *self.path_builder,
                        def);
             }
             _ => {
-                debug!("(iterating over each item of a module) processing \
-                        `%s` (%d:%d)",
+                debug2!("(iterating over each item of a module) processing \
+                        `{}` ({}:{})",
                        *self.path_builder,
                        def_id.crate,
                        def_id.node);
@@ -631,8 +631,8 @@ impl<'self> EachItemContext<'self> {
                 reader::get_doc(root, tag_items)
             };
 
-            debug!("(iterating over each item of a module) looking up item \
-                    %d:%d in `%s`, crate %d",
+            debug2!("(iterating over each item of a module) looking up item \
+                    {}:{} in `{}`, crate {}",
                    child_def_id.crate,
                    child_def_id.node,
                    *self.path_builder,
@@ -644,8 +644,8 @@ impl<'self> EachItemContext<'self> {
                 Some(child_item_doc) => {
                     // Push the name.
                     let child_name = item_name(self.intr, child_item_doc);
-                    debug!("(iterating over each item of a module) pushing \
-                            name `%s` onto `%s`",
+                    debug2!("(iterating over each item of a module) pushing \
+                            name `{}` onto `{}`",
                            token::ident_to_str(&child_name),
                            *self.path_builder);
                     let old_len =
@@ -682,9 +682,9 @@ impl<'self> EachItemContext<'self> {
             let name = name_doc.as_str_slice();
 
             // Push the name.
-            debug!("(iterating over each item of a module) pushing \
-                    reexported name `%s` onto `%s` (crate %d, orig %d, \
-                    in crate %d)",
+            debug2!("(iterating over each item of a module) pushing \
+                    reexported name `{}` onto `{}` (crate {}, orig {}, \
+                    in crate {})",
                    name,
                    *self.path_builder,
                    def_id.crate,
@@ -899,7 +899,7 @@ pub fn maybe_get_item_ast(cdata: Cmd, tcx: ty::ctxt,
                           id: ast::NodeId,
                           decode_inlined_item: decode_inlined_item)
                        -> csearch::found_ast {
-    debug!("Looking up item: %d", id);
+    debug2!("Looking up item: {}", id);
     let item_doc = lookup_item(id, cdata.data);
     let path = {
         let item_path = item_path(item_doc);
@@ -964,7 +964,7 @@ fn get_explicit_self(item: ebml::Doc) -> ast::explicit_self_ {
         match ch as char {
             'i' => ast::MutImmutable,
             'm' => ast::MutMutable,
-            _ => fail!("unknown mutability character: `%c`", ch as char),
+            _ => fail2!("unknown mutability character: `{}`", ch as char),
         }
     }
 
@@ -982,7 +982,7 @@ fn get_explicit_self(item: ebml::Doc) -> ast::explicit_self_ {
             return ast::sty_region(None, get_mutability(string[1]));
         }
         _ => {
-            fail!("unknown self type code: `%c`", explicit_self_kind as char);
+            fail2!("unknown self type code: `{}`", explicit_self_kind as char);
         }
     }
 }
@@ -1163,7 +1163,7 @@ pub fn get_static_methods_if_impl(intr: @ident_interner,
                 match item_family(impl_method_doc) {
                     StaticMethod => purity = ast::impure_fn,
                     UnsafeStaticMethod => purity = ast::unsafe_fn,
-                    _ => fail!()
+                    _ => fail2!()
                 }
 
                 static_impl_methods.push(StaticMethodInfo {
@@ -1199,7 +1199,7 @@ fn struct_field_family_to_visibility(family: Family) -> ast::visibility {
       PublicField => ast::public,
       PrivateField => ast::private,
       InheritedField => ast::inherited,
-      _ => fail!()
+      _ => fail2!()
     }
 }
 
@@ -1265,7 +1265,7 @@ fn describe_def(items: ebml::Doc, id: ast::DefId) -> ~str {
     if id.crate != ast::LOCAL_CRATE { return ~"external"; }
     let it = match maybe_find_item(id.node, items) {
         Some(it) => it,
-        None => fail!("describe_def: item not found %?", id)
+        None => fail2!("describe_def: item not found {:?}", id)
     };
     return item_family_to_str(item_family(it));
 }
@@ -1355,17 +1355,17 @@ fn list_meta_items(intr: @ident_interner,
                    out: @io::Writer) {
     let r = get_meta_items(meta_items);
     for mi in r.iter() {
-        out.write_str(fmt!("%s\n", pprust::meta_item_to_str(*mi, intr)));
+        out.write_str(format!("{}\n", pprust::meta_item_to_str(*mi, intr)));
     }
 }
 
 fn list_crate_attributes(intr: @ident_interner, md: ebml::Doc, hash: &str,
                          out: @io::Writer) {
-    out.write_str(fmt!("=Crate Attributes (%s)=\n", hash));
+    out.write_str(format!("=Crate Attributes ({})=\n", hash));
 
     let r = get_attributes(md);
     for attr in r.iter() {
-        out.write_str(fmt!("%s\n", pprust::attribute_to_str(attr, intr)));
+        out.write_str(format!("{}\n", pprust::attribute_to_str(attr, intr)));
     }
 
     out.write_str("\n\n");
@@ -1409,7 +1409,7 @@ fn list_crate_deps(data: @~[u8], out: @io::Writer) {
     let r = get_crate_deps(data);
     for dep in r.iter() {
         out.write_str(
-            fmt!("%d %s-%s-%s\n",
+            format!("{} {}-{}-{}\n",
                  dep.cnum, token::ident_to_str(&dep.name), dep.hash, dep.vers));
     }
 
@@ -1452,7 +1452,7 @@ pub fn translate_def_id(cdata: Cmd, did: ast::DefId) -> ast::DefId {
 
     match cdata.cnum_map.find(&did.crate) {
       option::Some(&n) => ast::DefId { crate: n, node: did.node },
-      option::None => fail!("didn't find a crate in the cnum_map")
+      option::None => fail2!("didn't find a crate in the cnum_map")
     }
 }
 
diff --git a/src/librustc/metadata/encoder.rs b/src/librustc/metadata/encoder.rs
index f84d9764714..ff59376aa37 100644
--- a/src/librustc/metadata/encoder.rs
+++ b/src/librustc/metadata/encoder.rs
@@ -185,7 +185,7 @@ fn encode_family(ebml_w: &mut writer::Encoder, c: char) {
 }
 
 pub fn def_to_str(did: DefId) -> ~str {
-    fmt!("%d:%d", did.crate, did.node)
+    format!("{}:{}", did.crate, did.node)
 }
 
 fn encode_ty_type_param_defs(ebml_w: &mut writer::Encoder,
@@ -284,12 +284,12 @@ fn encode_symbol(ecx: &EncodeContext,
     ebml_w.start_tag(tag_items_data_item_symbol);
     match ecx.item_symbols.find(&id) {
         Some(x) => {
-            debug!("encode_symbol(id=%?, str=%s)", id, *x);
+            debug2!("encode_symbol(id={:?}, str={})", id, *x);
             ebml_w.writer.write(x.as_bytes());
         }
         None => {
             ecx.diag.handler().bug(
-                fmt!("encode_symbol: id not found %d", id));
+                format!("encode_symbol: id not found {}", id));
         }
     }
     ebml_w.end_tag();
@@ -339,7 +339,7 @@ fn encode_enum_variant_info(ecx: &EncodeContext,
                             path: &[ast_map::path_elt],
                             index: @mut ~[entry<i64>],
                             generics: &ast::Generics) {
-    debug!("encode_enum_variant_info(id=%?)", id);
+    debug2!("encode_enum_variant_info(id={:?})", id);
 
     let mut disr_val = 0;
     let mut i = 0;
@@ -425,14 +425,14 @@ fn encode_reexported_static_method(ecx: &EncodeContext,
                                    exp: &middle::resolve::Export2,
                                    method_def_id: DefId,
                                    method_ident: Ident) {
-    debug!("(encode reexported static method) %s::%s",
+    debug2!("(encode reexported static method) {}::{}",
             exp.name, ecx.tcx.sess.str_of(method_ident));
     ebml_w.start_tag(tag_items_data_item_reexport);
     ebml_w.start_tag(tag_items_data_item_reexport_def_id);
     ebml_w.wr_str(def_to_str(method_def_id));
     ebml_w.end_tag();
     ebml_w.start_tag(tag_items_data_item_reexport_name);
-    ebml_w.wr_str(fmt!("%s::%s", exp.name, ecx.tcx.sess.str_of(method_ident)));
+    ebml_w.wr_str(format!("{}::{}", exp.name, ecx.tcx.sess.str_of(method_ident)));
     ebml_w.end_tag();
     ebml_w.end_tag();
 }
@@ -498,14 +498,14 @@ fn encode_reexported_static_methods(ecx: &EncodeContext,
             if mod_path != *path || exp.name != original_name {
                 if !encode_reexported_static_base_methods(ecx, ebml_w, exp) {
                     if encode_reexported_static_trait_methods(ecx, ebml_w, exp) {
-                        debug!(fmt!("(encode reexported static methods) %s \
-                                    [trait]",
-                                    original_name));
+                        debug2!("(encode reexported static methods) {} \
+                                 [trait]",
+                                original_name);
                     }
                 }
                 else {
-                    debug!(fmt!("(encode reexported static methods) %s [base]",
-                                original_name));
+                    debug2!("(encode reexported static methods) {} [base]",
+                            original_name);
                 }
             }
         }
@@ -552,13 +552,13 @@ fn encode_reexports(ecx: &EncodeContext,
                     ebml_w: &mut writer::Encoder,
                     id: NodeId,
                     path: &[ast_map::path_elt]) {
-    debug!("(encoding info for module) encoding reexports for %d", id);
+    debug2!("(encoding info for module) encoding reexports for {}", id);
     match ecx.reexports2.find(&id) {
         Some(ref exports) => {
-            debug!("(encoding info for module) found reexports for %d", id);
+            debug2!("(encoding info for module) found reexports for {}", id);
             for exp in exports.iter() {
-                debug!("(encoding info for module) reexport '%s' (%d/%d) for \
-                        %d",
+                debug2!("(encoding info for module) reexport '{}' ({}/{}) for \
+                        {}",
                        exp.name,
                        exp.def_id.crate,
                        exp.def_id.node,
@@ -575,7 +575,7 @@ fn encode_reexports(ecx: &EncodeContext,
             }
         }
         None => {
-            debug!("(encoding info for module) found no reexports for %d",
+            debug2!("(encoding info for module) found no reexports for {}",
                    id);
         }
     }
@@ -592,7 +592,7 @@ fn encode_info_for_mod(ecx: &EncodeContext,
     encode_def_id(ebml_w, local_def(id));
     encode_family(ebml_w, 'm');
     encode_name(ecx, ebml_w, name);
-    debug!("(encoding info for module) encoding info for module ID %d", id);
+    debug2!("(encoding info for module) encoding info for module ID {}", id);
 
     // Encode info about all the module children.
     for item in md.items.iter() {
@@ -610,8 +610,8 @@ fn encode_info_for_mod(ecx: &EncodeContext,
         match item.node {
             item_impl(*) => {
                 let (ident, did) = (item.ident, item.id);
-                debug!("(encoding info for module) ... encoding impl %s \
-                        (%?/%?)",
+                debug2!("(encoding info for module) ... encoding impl {} \
+                        ({:?}/{:?})",
                         ecx.tcx.sess.str_of(ident),
                         did,
                         ast_map::node_id_to_str(ecx.tcx.items, did, token::get_ident_interner()));
@@ -628,7 +628,7 @@ fn encode_info_for_mod(ecx: &EncodeContext,
 
     // Encode the reexports of this module, if this module is public.
     if vis == public {
-        debug!("(encoding info for module) encoding reexports for %d", id);
+        debug2!("(encoding info for module) encoding reexports for {}", id);
         encode_reexports(ecx, ebml_w, id, path);
     }
 
@@ -730,7 +730,7 @@ fn encode_info_for_struct(ecx: &EncodeContext,
         index.push(entry {val: id as i64, pos: ebml_w.writer.tell()});
         global_index.push(entry {val: id as i64, pos: ebml_w.writer.tell()});
         ebml_w.start_tag(tag_items_data_item);
-        debug!("encode_info_for_struct: doing %s %d",
+        debug2!("encode_info_for_struct: doing {} {}",
                tcx.sess.str_of(nm), id);
         encode_struct_field_family(ebml_w, vis);
         encode_name(ecx, ebml_w, nm);
@@ -794,7 +794,7 @@ fn encode_info_for_method(ecx: &EncodeContext,
                           parent_id: NodeId,
                           ast_method_opt: Option<@method>) {
 
-    debug!("encode_info_for_method: %? %s", m.def_id,
+    debug2!("encode_info_for_method: {:?} {}", m.def_id,
            ecx.tcx.sess.str_of(m.ident));
     ebml_w.start_tag(tag_items_data_item);
 
@@ -834,7 +834,7 @@ fn purity_static_method_family(p: purity) -> char {
     match p {
       unsafe_fn => 'U',
       impure_fn => 'F',
-      _ => fail!("extern fn can't be static")
+      _ => fail2!("extern fn can't be static")
     }
 }
 
@@ -893,7 +893,7 @@ fn encode_info_for_item(ecx: &EncodeContext,
     }
     let add_to_index: &fn() = || add_to_index_(item, ebml_w, index);
 
-    debug!("encoding info for item at %s",
+    debug2!("encoding info for item at {}",
            ecx.tcx.sess.codemap.span_to_str(item.span));
 
     let def_id = local_def(item.id);
@@ -1220,7 +1220,7 @@ fn encode_info_for_item(ecx: &EncodeContext,
         // Encode inherent implementations for this trait.
         encode_inherent_implementations(ecx, ebml_w, def_id);
       }
-      item_mac(*) => fail!("item macros unimplemented")
+      item_mac(*) => fail2!("item macros unimplemented")
     }
 }
 
@@ -1279,7 +1279,7 @@ fn my_visit_item(i:@item, items: ast_map::map, ebml_w:&writer::Encoder,
             };
             encode_info_for_item(ecx, &mut ebml_w, i, index, *pt, vis);
         }
-        _ => fail!("bad item")
+        _ => fail2!("bad item")
     }
 }
 
@@ -1287,7 +1287,7 @@ fn my_visit_foreign_item(ni:@foreign_item, items: ast_map::map, ebml_w:&writer::
                          ecx_ptr:*int, index: @mut ~[entry<i64>]) {
     match items.get_copy(&ni.id) {
         ast_map::node_foreign_item(_, abi, _, pt) => {
-            debug!("writing foreign item %s::%s",
+            debug2!("writing foreign item {}::{}",
                    ast_map::path_to_str(
                        *pt,
                        token::get_ident_interner()),
@@ -1304,7 +1304,7 @@ fn my_visit_foreign_item(ni:@foreign_item, items: ast_map::map, ebml_w:&writer::
                                          abi);
         }
         // case for separate item and foreign-item tables
-        _ => fail!("bad foreign item")
+        _ => fail2!("bad foreign item")
     }
 }
 
diff --git a/src/librustc/metadata/filesearch.rs b/src/librustc/metadata/filesearch.rs
index c719146c999..6761445b74e 100644
--- a/src/librustc/metadata/filesearch.rs
+++ b/src/librustc/metadata/filesearch.rs
@@ -53,7 +53,7 @@ pub fn mk_filesearch(maybe_sysroot: &Option<@Path>,
             let mut visited_dirs = HashSet::new();
             let mut found = false;
 
-            debug!("filesearch: searching additional lib search paths [%?]",
+            debug2!("filesearch: searching additional lib search paths [{:?}]",
                    self.addl_lib_search_paths.len());
             for path in self.addl_lib_search_paths.iter() {
                 match f(path) {
@@ -63,7 +63,7 @@ pub fn mk_filesearch(maybe_sysroot: &Option<@Path>,
                 visited_dirs.insert(path.to_str());
             }
 
-            debug!("filesearch: searching target lib path");
+            debug2!("filesearch: searching target lib path");
             let tlib_path = make_target_lib_path(self.sysroot,
                                         self.target_triple);
             if !visited_dirs.contains(&tlib_path.to_str()) {
@@ -78,7 +78,7 @@ pub fn mk_filesearch(maybe_sysroot: &Option<@Path>,
                 let rustpath = rust_path();
                 for path in rustpath.iter() {
                     let tlib_path = make_rustpkg_target_lib_path(path, self.target_triple);
-                    debug!("is %s in visited_dirs? %?", tlib_path.to_str(),
+                    debug2!("is {} in visited_dirs? {:?}", tlib_path.to_str(),
                             visited_dirs.contains(&tlib_path.to_str()));
 
                     if !visited_dirs.contains(&tlib_path.to_str()) {
@@ -104,7 +104,7 @@ pub fn mk_filesearch(maybe_sysroot: &Option<@Path>,
     }
 
     let sysroot = get_sysroot(maybe_sysroot);
-    debug!("using sysroot = %s", sysroot.to_str());
+    debug2!("using sysroot = {}", sysroot.to_str());
     @FileSearchImpl {
         sysroot: sysroot,
         addl_lib_search_paths: addl_lib_search_paths,
@@ -114,19 +114,19 @@ pub fn mk_filesearch(maybe_sysroot: &Option<@Path>,
 
 pub fn search(filesearch: @FileSearch, pick: pick) {
     do filesearch.for_each_lib_search_path() |lib_search_path| {
-        debug!("searching %s", lib_search_path.to_str());
+        debug2!("searching {}", lib_search_path.to_str());
         let r = os::list_dir_path(lib_search_path);
         let mut rslt = FileDoesntMatch;
         for path in r.iter() {
-            debug!("testing %s", path.to_str());
+            debug2!("testing {}", path.to_str());
             let maybe_picked = pick(path);
             match maybe_picked {
                 FileMatches => {
-                    debug!("picked %s", path.to_str());
+                    debug2!("picked {}", path.to_str());
                     rslt = FileMatches;
                 }
                 FileDoesntMatch => {
-                    debug!("rejected %s", path.to_str());
+                    debug2!("rejected {}", path.to_str());
                 }
             }
         }
@@ -153,7 +153,7 @@ fn make_rustpkg_target_lib_path(dir: &Path,
 pub fn get_or_default_sysroot() -> Path {
     match os::self_exe_path() {
       option::Some(ref p) => (*p).pop(),
-      option::None => fail!("can't determine value for sysroot")
+      option::None => fail2!("can't determine value for sysroot")
     }
 }
 
diff --git a/src/librustc/metadata/loader.rs b/src/librustc/metadata/loader.rs
index b5ba9bb5648..4d69a2ffce8 100644
--- a/src/librustc/metadata/loader.rs
+++ b/src/librustc/metadata/loader.rs
@@ -59,7 +59,7 @@ pub fn load_library_crate(cx: &Context) -> (~str, @~[u8]) {
       Some(t) => t,
       None => {
         cx.diag.span_fatal(cx.span,
-                           fmt!("can't find crate for `%s`",
+                           format!("can't find crate for `{}`",
                                 cx.ident));
       }
     }
@@ -90,7 +90,7 @@ fn find_library_crate_aux(
 ) -> Option<(~str, @~[u8])> {
     let crate_name = crate_name_from_metas(cx.metas);
     // want: crate_name.dir_part() + prefix + crate_name.file_part + "-"
-    let prefix = fmt!("%s%s-", prefix, crate_name);
+    let prefix = format!("{}{}-", prefix, crate_name);
     let mut matches = ~[];
     filesearch::search(filesearch, |path| -> FileMatch {
       let path_str = path.filename();
@@ -98,20 +98,20 @@ fn find_library_crate_aux(
           None => FileDoesntMatch,
           Some(path_str) =>
               if path_str.starts_with(prefix) && path_str.ends_with(suffix) {
-                  debug!("%s is a candidate", path.to_str());
+                  debug2!("{} is a candidate", path.to_str());
                   match get_metadata_section(cx.os, path) {
                       Some(cvec) =>
                           if !crate_matches(cvec, cx.metas, cx.hash) {
-                              debug!("skipping %s, metadata doesn't match",
+                              debug2!("skipping {}, metadata doesn't match",
                                   path.to_str());
                               FileDoesntMatch
                           } else {
-                              debug!("found %s with matching metadata", path.to_str());
+                              debug2!("found {} with matching metadata", path.to_str());
                               matches.push((path.to_str(), cvec));
                               FileMatches
                           },
                       _ => {
-                          debug!("could not load metadata for %s", path.to_str());
+                          debug2!("could not load metadata for {}", path.to_str());
                           FileDoesntMatch
                       }
                   }
@@ -127,12 +127,12 @@ fn find_library_crate_aux(
         1 => Some(matches[0]),
         _ => {
             cx.diag.span_err(
-                    cx.span, fmt!("multiple matching crates for `%s`", crate_name));
+                    cx.span, format!("multiple matching crates for `{}`", crate_name));
                 cx.diag.handler().note("candidates:");
                 for pair in matches.iter() {
                     let ident = pair.first();
                     let data = pair.second();
-                    cx.diag.handler().note(fmt!("path: %s", ident));
+                    cx.diag.handler().note(format!("path: {}", ident));
                     let attrs = decoder::get_crate_attributes(data);
                     note_linkage_attrs(cx.intr, cx.diag, attrs);
                 }
@@ -149,7 +149,7 @@ pub fn crate_name_from_metas(metas: &[@ast::MetaItem]) -> @str {
             _ => {}
         }
     }
-    fail!("expected to find the crate name")
+    fail2!("expected to find the crate name")
 }
 
 pub fn package_id_from_metas(metas: &[@ast::MetaItem]) -> Option<@str> {
@@ -167,7 +167,7 @@ pub fn note_linkage_attrs(intr: @ident_interner,
                           attrs: ~[ast::Attribute]) {
     let r = attr::find_linkage_metas(attrs);
     for mi in r.iter() {
-        diag.handler().note(fmt!("meta: %s", pprust::meta_item_to_str(*mi,intr)));
+        diag.handler().note(format!("meta: {}", pprust::meta_item_to_str(*mi,intr)));
     }
 }
 
@@ -188,7 +188,7 @@ pub fn metadata_matches(extern_metas: &[@ast::MetaItem],
 
 // extern_metas: metas we read from the crate
 // local_metas: metas we're looking for
-    debug!("matching %u metadata requirements against %u items",
+    debug2!("matching {} metadata requirements against {} items",
            local_metas.len(), extern_metas.len());
 
     do local_metas.iter().all |needed| {
@@ -211,14 +211,14 @@ fn get_metadata_section(os: Os,
         while llvm::LLVMIsSectionIteratorAtEnd(of.llof, si.llsi) == False {
             let name_buf = llvm::LLVMGetSectionName(si.llsi);
             let name = str::raw::from_c_str(name_buf);
-            debug!("get_metadata_section: name %s", name);
+            debug2!("get_metadata_section: name {}", name);
             if read_meta_section_name(os) == name {
                 let cbuf = llvm::LLVMGetSectionContents(si.llsi);
                 let csz = llvm::LLVMGetSectionSize(si.llsi) as uint;
                 let mut found = None;
                 let cvbuf: *u8 = cast::transmute(cbuf);
                 let vlen = encoder::metadata_encoding_version.len();
-                debug!("checking %u bytes of metadata-version stamp",
+                debug2!("checking {} bytes of metadata-version stamp",
                        vlen);
                 let minsz = num::min(vlen, csz);
                 let mut version_ok = false;
@@ -229,7 +229,7 @@ fn get_metadata_section(os: Os,
                 if !version_ok { return None; }
 
                 let cvbuf1 = ptr::offset(cvbuf, vlen as int);
-                debug!("inflating %u bytes of compressed metadata",
+                debug2!("inflating {} bytes of compressed metadata",
                        csz - vlen);
                 do vec::raw::buf_as_slice(cvbuf1, csz-vlen) |bytes| {
                     let inflated = flate::inflate_bytes(bytes);
@@ -273,7 +273,7 @@ pub fn list_file_metadata(intr: @ident_interner,
     match get_metadata_section(os, path) {
       option::Some(bytes) => decoder::list_crate_metadata(intr, bytes, out),
       option::None => {
-        out.write_str(fmt!("could not find metadata in %s.\n", path.to_str()))
+        out.write_str(format!("could not find metadata in {}.\n", path.to_str()))
       }
     }
 }
diff --git a/src/librustc/metadata/tydecode.rs b/src/librustc/metadata/tydecode.rs
index b94a43e07a1..b44051ef560 100644
--- a/src/librustc/metadata/tydecode.rs
+++ b/src/librustc/metadata/tydecode.rs
@@ -80,10 +80,10 @@ fn scan<R>(st: &mut PState, is_last: &fn(char) -> bool,
            op: &fn(&[u8]) -> R) -> R
 {
     let start_pos = st.pos;
-    debug!("scan: '%c' (start)", st.data[st.pos] as char);
+    debug2!("scan: '{}' (start)", st.data[st.pos] as char);
     while !is_last(st.data[st.pos] as char) {
         st.pos += 1;
-        debug!("scan: '%c'", st.data[st.pos] as char);
+        debug2!("scan: '{}'", st.data[st.pos] as char);
     }
     let end_pos = st.pos;
     st.pos += 1;
@@ -161,7 +161,7 @@ fn parse_sigil(st: &mut PState) -> ast::Sigil {
         '@' => ast::ManagedSigil,
         '~' => ast::OwnedSigil,
         '&' => ast::BorrowedSigil,
-        c => st.tcx.sess.bug(fmt!("parse_sigil(): bad input '%c'", c))
+        c => st.tcx.sess.bug(format!("parse_sigil(): bad input '{}'", c))
     }
 }
 
@@ -179,7 +179,7 @@ fn parse_vstore(st: &mut PState) -> ty::vstore {
       '~' => ty::vstore_uniq,
       '@' => ty::vstore_box,
       '&' => ty::vstore_slice(parse_region(st)),
-      c => st.tcx.sess.bug(fmt!("parse_vstore(): bad input '%c'", c))
+      c => st.tcx.sess.bug(format!("parse_vstore(): bad input '{}'", c))
     }
 }
 
@@ -188,7 +188,7 @@ fn parse_trait_store(st: &mut PState) -> ty::TraitStore {
         '~' => ty::UniqTraitStore,
         '@' => ty::BoxTraitStore,
         '&' => ty::RegionTraitStore(parse_region(st)),
-        c => st.tcx.sess.bug(fmt!("parse_trait_store(): bad input '%c'", c))
+        c => st.tcx.sess.bug(format!("parse_trait_store(): bad input '{}'", c))
     }
 }
 
@@ -221,7 +221,7 @@ fn parse_region_substs(st: &mut PState) -> ty::RegionSubsts {
             assert_eq!(next(st), '.');
             ty::NonerasedRegions(regions)
         }
-        _ => fail!("parse_bound_region: bad input")
+        _ => fail2!("parse_bound_region: bad input")
     }
 }
 
@@ -239,7 +239,7 @@ fn parse_bound_region(st: &mut PState) -> ty::bound_region {
         assert_eq!(next(st), '|');
         ty::br_cap_avoid(id, @parse_bound_region(st))
       },
-      _ => fail!("parse_bound_region: bad input")
+      _ => fail2!("parse_bound_region: bad input")
     }
 }
 
@@ -268,7 +268,7 @@ fn parse_region(st: &mut PState) -> ty::Region {
       'e' => {
         ty::re_static
       }
-      _ => fail!("parse_region: bad input")
+      _ => fail2!("parse_region: bad input")
     }
 }
 
@@ -276,7 +276,7 @@ fn parse_opt<T>(st: &mut PState, f: &fn(&mut PState) -> T) -> Option<T> {
     match next(st) {
       'n' => None,
       's' => Some(f(st)),
-      _ => fail!("parse_opt: bad input")
+      _ => fail2!("parse_opt: bad input")
     }
 }
 
@@ -317,7 +317,7 @@ fn parse_ty(st: &mut PState, conv: conv_did) -> ty::t {
           'D' => return ty::mk_mach_int(ast::ty_i64),
           'f' => return ty::mk_mach_float(ast::ty_f32),
           'F' => return ty::mk_mach_float(ast::ty_f64),
-          _ => fail!("parse_ty: bad numeric type")
+          _ => fail2!("parse_ty: bad numeric type")
         }
       }
       'c' => return ty::mk_char(),
@@ -340,7 +340,7 @@ fn parse_ty(st: &mut PState, conv: conv_did) -> ty::t {
       }
       'p' => {
         let did = parse_def(st, TypeParameter, conv);
-        debug!("parsed ty_param: did=%?", did);
+        debug2!("parsed ty_param: did={:?}", did);
         return ty::mk_param(st.tcx, parse_uint(st), did);
       }
       's' => {
@@ -417,7 +417,7 @@ fn parse_ty(st: &mut PState, conv: conv_did) -> ty::t {
           assert_eq!(next(st), ']');
           return ty::mk_struct(st.tcx, did, substs);
       }
-      c => { error!("unexpected char in type string: %c", c); fail!();}
+      c => { error2!("unexpected char in type string: {}", c); fail2!();}
     }
 }
 
@@ -467,7 +467,7 @@ fn parse_purity(c: char) -> purity {
       'u' => unsafe_fn,
       'i' => impure_fn,
       'c' => extern_fn,
-      _ => fail!("parse_purity: bad purity %c", c)
+      _ => fail2!("parse_purity: bad purity {}", c)
     }
 }
 
@@ -488,7 +488,7 @@ fn parse_onceness(c: char) -> ast::Onceness {
     match c {
         'o' => ast::Once,
         'm' => ast::Many,
-        _ => fail!("parse_onceness: bad onceness")
+        _ => fail2!("parse_onceness: bad onceness")
     }
 }
 
@@ -539,8 +539,8 @@ pub fn parse_def_id(buf: &[u8]) -> ast::DefId {
     let len = buf.len();
     while colon_idx < len && buf[colon_idx] != ':' as u8 { colon_idx += 1u; }
     if colon_idx == len {
-        error!("didn't find ':' when parsing def id");
-        fail!();
+        error2!("didn't find ':' when parsing def id");
+        fail2!();
     }
 
     let crate_part = buf.slice(0u, colon_idx);
@@ -548,12 +548,12 @@ pub fn parse_def_id(buf: &[u8]) -> ast::DefId {
 
     let crate_num = match uint::parse_bytes(crate_part, 10u) {
        Some(cn) => cn as int,
-       None => fail!("internal error: parse_def_id: crate number expected, but found %?",
+       None => fail2!("internal error: parse_def_id: crate number expected, but found {:?}",
                      crate_part)
     };
     let def_num = match uint::parse_bytes(def_part, 10u) {
        Some(dn) => dn as int,
-       None => fail!("internal error: parse_def_id: id expected, but found %?",
+       None => fail2!("internal error: parse_def_id: id expected, but found {:?}",
                      def_part)
     };
     ast::DefId { crate: crate_num, node: def_num }
@@ -599,7 +599,7 @@ fn parse_bounds(st: &mut PState, conv: conv_did) -> ty::ParamBounds {
                 return param_bounds;
             }
             _ => {
-                fail!("parse_bounds: bad bounds")
+                fail2!("parse_bounds: bad bounds")
             }
         }
     }
diff --git a/src/librustc/metadata/tyencode.rs b/src/librustc/metadata/tyencode.rs
index 417a6dae7be..09c776a9fab 100644
--- a/src/librustc/metadata/tyencode.rs
+++ b/src/librustc/metadata/tyencode.rs
@@ -86,7 +86,7 @@ pub fn enc_ty(w: @io::Writer, cx: @ctxt, t: ty::t) {
           let abbrev_len = 3u + estimate_sz(pos) + estimate_sz(len);
           if abbrev_len < len {
               // I.e. it's actually an abbreviation.
-              let s = fmt!("#%x:%x#", pos, len).to_managed();
+              let s = format!("\\#{:x}:{:x}\\#", pos, len).to_managed();
               let a = ty_abbrev { pos: pos, len: len, s: s };
               abbrevs.insert(t, a);
           }
@@ -336,18 +336,18 @@ fn enc_sty(w: @io::Writer, cx: @ctxt, st: &ty::sty) {
       }
       ty::ty_opaque_box => w.write_char('B'),
       ty::ty_struct(def, ref substs) => {
-          debug!("~~~~ %s", "a[");
+          debug2!("~~~~ {}", "a[");
           w.write_str(&"a[");
           let s = (cx.ds)(def);
-          debug!("~~~~ %s", s);
+          debug2!("~~~~ {}", s);
           w.write_str(s);
-          debug!("~~~~ %s", "|");
+          debug2!("~~~~ {}", "|");
           w.write_char('|');
           enc_substs(w, cx, substs);
-          debug!("~~~~ %s", "]");
+          debug2!("~~~~ {}", "]");
           w.write_char(']');
       }
-      ty::ty_err => fail!("Shouldn't encode error type")
+      ty::ty_err => fail2!("Shouldn't encode error type")
     }
 }
 
diff --git a/src/librustc/middle/astencode.rs b/src/librustc/middle/astencode.rs
index 683fbba09cc..902f90eb7cd 100644
--- a/src/librustc/middle/astencode.rs
+++ b/src/librustc/middle/astencode.rs
@@ -84,7 +84,7 @@ pub fn encode_inlined_item(ecx: &e::EncodeContext,
                            path: &[ast_map::path_elt],
                            ii: ast::inlined_item,
                            maps: Maps) {
-    debug!("> Encoding inlined item: %s::%s (%u)",
+    debug2!("> Encoding inlined item: {}::{} ({})",
            ast_map::path_to_str(path, token::get_ident_interner()),
            ecx.tcx.sess.str_of(ii.ident()),
            ebml_w.writer.tell());
@@ -97,7 +97,7 @@ pub fn encode_inlined_item(ecx: &e::EncodeContext,
     encode_side_tables_for_ii(ecx, maps, ebml_w, &ii);
     ebml_w.end_tag();
 
-    debug!("< Encoded inlined fn: %s::%s (%u)",
+    debug2!("< Encoded inlined fn: {}::{} ({})",
            ast_map::path_to_str(path, token::get_ident_interner()),
            ecx.tcx.sess.str_of(ii.ident()),
            ebml_w.writer.tell());
@@ -117,7 +117,7 @@ pub fn decode_inlined_item(cdata: @cstore::crate_metadata,
     match par_doc.opt_child(c::tag_ast) {
       None => None,
       Some(ast_doc) => {
-        debug!("> Decoding inlined fn: %s::?",
+        debug2!("> Decoding inlined fn: {}::?",
                ast_map::path_to_str(path, token::get_ident_interner()));
         let mut ast_dsr = reader::Decoder(ast_doc);
         let from_id_range = Decodable::decode(&mut ast_dsr);
@@ -129,8 +129,8 @@ pub fn decode_inlined_item(cdata: @cstore::crate_metadata,
         };
         let raw_ii = decode_ast(ast_doc);
         let ii = renumber_ast(xcx, raw_ii);
-        debug!("Fn named: %s", tcx.sess.str_of(ii.ident()));
-        debug!("< Decoded inlined fn: %s::%s",
+        debug2!("Fn named: {}", tcx.sess.str_of(ii.ident()));
+        debug2!("< Decoded inlined fn: {}::{}",
                ast_map::path_to_str(path, token::get_ident_interner()),
                tcx.sess.str_of(ii.ident()));
         ast_map::map_decoded_item(tcx.sess.diagnostic(),
@@ -140,7 +140,7 @@ pub fn decode_inlined_item(cdata: @cstore::crate_metadata,
         decode_side_tables(xcx, ast_doc);
         match ii {
           ast::ii_item(i) => {
-            debug!(">>> DECODED ITEM >>>\n%s\n<<< DECODED ITEM <<<",
+            debug2!(">>> DECODED ITEM >>>\n{}\n<<< DECODED ITEM <<<",
                    syntax::print::pprust::item_to_str(i, tcx.sess.intr()));
           }
           _ => { }
@@ -305,7 +305,7 @@ impl fold::ast_fold for NestedItemsDropper {
                     node: ast::DeclItem(_),
                     span: _
                 }, _) => None,
-                ast::StmtMac(*) => fail!("unexpanded macro in astencode")
+                ast::StmtMac(*) => fail2!("unexpanded macro in astencode")
             }
         }.collect();
         let blk_sans_items = ast::Block {
@@ -741,7 +741,7 @@ impl vtable_decoder_helpers for reader::Decoder {
                     )
                   }
                   // hard to avoid - user input
-                  _ => fail!("bad enum variant")
+                  _ => fail2!("bad enum variant")
                 }
             }
         }
@@ -896,7 +896,7 @@ fn encode_side_tables_for_id(ecx: &e::EncodeContext,
                              id: ast::NodeId) {
     let tcx = ecx.tcx;
 
-    debug!("Encoding side tables for id %d", id);
+    debug2!("Encoding side tables for id {}", id);
 
     {
         let r = tcx.def_map.find(&id);
@@ -1091,7 +1091,7 @@ impl ebml_decoder_decoder_helpers for reader::Decoder {
                 xcx.dcx.tcx,
                 |s, a| this.convert_def_id(xcx, s, a));
 
-            debug!("read_ty(%s) = %s",
+            debug2!("read_ty({}) = {}",
                    type_string(doc),
                    ty_to_str(xcx.dcx.tcx, ty));
 
@@ -1176,7 +1176,7 @@ impl ebml_decoder_decoder_helpers for reader::Decoder {
             NominalType | TypeWithId => xcx.tr_def_id(did),
             TypeParameter => xcx.tr_intern_def_id(did)
         };
-        debug!("convert_def_id(source=%?, did=%?)=%?", source, did, r);
+        debug2!("convert_def_id(source={:?}, did={:?})={:?}", source, did, r);
         return r;
     }
 }
@@ -1189,14 +1189,14 @@ fn decode_side_tables(xcx: @ExtendedDecodeContext,
         let id0 = entry_doc.get(c::tag_table_id as uint).as_int();
         let id = xcx.tr_id(id0);
 
-        debug!(">> Side table document with tag 0x%x \
-                found for id %d (orig %d)",
+        debug2!(">> Side table document with tag 0x{:x} \
+                found for id {} (orig {})",
                tag, id, id0);
 
         match c::astencode_tag::from_uint(tag) {
             None => {
                 xcx.dcx.tcx.sess.bug(
-                    fmt!("unknown tag found in side tables: %x", tag));
+                    format!("unknown tag found in side tables: {:x}", tag));
             }
             Some(value) => {
                 let val_doc = entry_doc.get(c::tag_table_val as uint);
@@ -1210,7 +1210,7 @@ fn decode_side_tables(xcx: @ExtendedDecodeContext,
                     }
                     c::tag_table_node_type => {
                         let ty = val_dsr.read_ty(xcx);
-                        debug!("inserting ty for node %?: %s",
+                        debug2!("inserting ty for node {:?}: {}",
                                id, ty_to_str(dcx.tcx, ty));
                         dcx.tcx.node_types.insert(id as uint, ty);
                     }
@@ -1257,13 +1257,13 @@ fn decode_side_tables(xcx: @ExtendedDecodeContext,
                     }
                     _ => {
                         xcx.dcx.tcx.sess.bug(
-                            fmt!("unknown tag found in side tables: %x", tag));
+                            format!("unknown tag found in side tables: {:x}", tag));
                     }
                 }
             }
         }
 
-        debug!(">< Side table doc loaded");
+        debug2!(">< Side table doc loaded");
         true
     };
 }
@@ -1381,6 +1381,6 @@ fn test_simplification() {
                      == pprust::item_to_str(item_exp,
                                             token::get_ident_interner()));
       }
-      _ => fail!()
+      _ => fail2!()
     }
 }
diff --git a/src/librustc/middle/borrowck/check_loans.rs b/src/librustc/middle/borrowck/check_loans.rs
index e8e658abc37..5334bf7cc1d 100644
--- a/src/librustc/middle/borrowck/check_loans.rs
+++ b/src/librustc/middle/borrowck/check_loans.rs
@@ -65,7 +65,7 @@ pub fn check_loans(bccx: &BorrowckCtxt,
                    move_data: move_data::FlowedMoveData,
                    all_loans: &[Loan],
                    body: &ast::Block) {
-    debug!("check_loans(body id=%?)", body.id);
+    debug2!("check_loans(body id={:?})", body.id);
 
     let mut clcx = CheckLoanCtxt {
         bccx: bccx,
@@ -94,12 +94,12 @@ impl<'self> CheckLoanCtxt<'self> {
             MoveWhileBorrowed(loan_path, loan_span) => {
                 self.bccx.span_err(
                     cap_var.span,
-                    fmt!("cannot move `%s` into closure \
+                    format!("cannot move `{}` into closure \
                           because it is borrowed",
                          self.bccx.loan_path_to_str(move_path)));
                 self.bccx.span_note(
                     loan_span,
-                    fmt!("borrow of `%s` occurs here",
+                    format!("borrow of `{}` occurs here",
                          self.bccx.loan_path_to_str(loan_path)));
             }
         }
@@ -197,10 +197,10 @@ impl<'self> CheckLoanCtxt<'self> {
         //! issued when we enter `scope_id` (for example, we do not
         //! permit two `&mut` borrows of the same variable).
 
-        debug!("check_for_conflicting_loans(scope_id=%?)", scope_id);
+        debug2!("check_for_conflicting_loans(scope_id={:?})", scope_id);
 
         let new_loan_indices = self.loans_generated_by(scope_id);
-        debug!("new_loan_indices = %?", new_loan_indices);
+        debug2!("new_loan_indices = {:?}", new_loan_indices);
 
         do self.each_issued_loan(scope_id) |issued_loan| {
             for &new_loan_index in new_loan_indices.iter() {
@@ -225,7 +225,7 @@ impl<'self> CheckLoanCtxt<'self> {
         //! Checks whether `old_loan` and `new_loan` can safely be issued
         //! simultaneously.
 
-        debug!("report_error_if_loans_conflict(old_loan=%s, new_loan=%s)",
+        debug2!("report_error_if_loans_conflict(old_loan={}, new_loan={})",
                old_loan.repr(self.tcx()),
                new_loan.repr(self.tcx()));
 
@@ -249,8 +249,8 @@ impl<'self> CheckLoanCtxt<'self> {
         //! Checks whether the restrictions introduced by `loan1` would
         //! prohibit `loan2`. Returns false if an error is reported.
 
-        debug!("report_error_if_loan_conflicts_with_restriction(\
-                loan1=%s, loan2=%s)",
+        debug2!("report_error_if_loan_conflicts_with_restriction(\
+                loan1={}, loan2={})",
                loan1.repr(self.tcx()),
                loan2.repr(self.tcx()));
 
@@ -260,7 +260,7 @@ impl<'self> CheckLoanCtxt<'self> {
             ImmutableMutability => RESTR_ALIAS | RESTR_FREEZE,
             ConstMutability     => RESTR_ALIAS,
         };
-        debug!("illegal_if=%?", illegal_if);
+        debug2!("illegal_if={:?}", illegal_if);
 
         for restr in loan1.restrictions.iter() {
             if !restr.set.intersects(illegal_if) { loop; }
@@ -270,12 +270,12 @@ impl<'self> CheckLoanCtxt<'self> {
                 (MutableMutability, MutableMutability) => {
                     self.bccx.span_err(
                         new_loan.span,
-                        fmt!("cannot borrow `%s` as mutable \
+                        format!("cannot borrow `{}` as mutable \
                               more than once at a time",
                              self.bccx.loan_path_to_str(new_loan.loan_path)));
                     self.bccx.span_note(
                         old_loan.span,
-                        fmt!("second borrow of `%s` as mutable occurs here",
+                        format!("second borrow of `{}` as mutable occurs here",
                              self.bccx.loan_path_to_str(new_loan.loan_path)));
                     return false;
                 }
@@ -283,14 +283,14 @@ impl<'self> CheckLoanCtxt<'self> {
                 _ => {
                     self.bccx.span_err(
                         new_loan.span,
-                        fmt!("cannot borrow `%s` as %s because \
-                              it is also borrowed as %s",
+                        format!("cannot borrow `{}` as {} because \
+                              it is also borrowed as {}",
                              self.bccx.loan_path_to_str(new_loan.loan_path),
                              self.bccx.mut_to_str(new_loan.mutbl),
                              self.bccx.mut_to_str(old_loan.mutbl)));
                     self.bccx.span_note(
                         old_loan.span,
-                        fmt!("second borrow of `%s` occurs here",
+                        format!("second borrow of `{}` occurs here",
                              self.bccx.loan_path_to_str(new_loan.loan_path)));
                     return false;
                 }
@@ -317,7 +317,7 @@ impl<'self> CheckLoanCtxt<'self> {
          * is using a moved/uninitialized value
          */
 
-        debug!("check_if_path_is_moved(id=%?, use_kind=%?, lp=%s)",
+        debug2!("check_if_path_is_moved(id={:?}, use_kind={:?}, lp={})",
                id, use_kind, lp.repr(self.bccx.tcx));
         do self.move_data.each_move_of(id, lp) |move, moved_lp| {
             self.bccx.report_use_of_moved_value(
@@ -338,7 +338,7 @@ impl<'self> CheckLoanCtxt<'self> {
             Some(&adj) => self.bccx.cat_expr_autoderefd(expr, adj)
         };
 
-        debug!("check_assignment(cmt=%s)", cmt.repr(self.tcx()));
+        debug2!("check_assignment(cmt={})", cmt.repr(self.tcx()));
 
         // Mutable values can be assigned, as long as they obey loans
         // and aliasing restrictions:
@@ -372,7 +372,7 @@ impl<'self> CheckLoanCtxt<'self> {
         // Otherwise, just a plain error.
         self.bccx.span_err(
             expr.span,
-            fmt!("cannot assign to %s %s",
+            format!("cannot assign to {} {}",
                  cmt.mutbl.to_user_str(),
                  self.bccx.cmt_to_str(cmt)));
         return;
@@ -387,7 +387,7 @@ impl<'self> CheckLoanCtxt<'self> {
 
             let mut cmt = cmt;
             loop {
-                debug!("mark_writes_through_upvars_as_used_mut(cmt=%s)",
+                debug2!("mark_writes_through_upvars_as_used_mut(cmt={})",
                        cmt.repr(this.tcx()));
                 match cmt.cat {
                     mc::cat_local(id) |
@@ -435,7 +435,7 @@ impl<'self> CheckLoanCtxt<'self> {
             //! Safety checks related to writes to aliasable, mutable locations
 
             let guarantor = cmt.guarantor();
-            debug!("check_for_aliasable_mutable_writes(cmt=%s, guarantor=%s)",
+            debug2!("check_for_aliasable_mutable_writes(cmt={}, guarantor={})",
                    cmt.repr(this.tcx()), guarantor.repr(this.tcx()));
             match guarantor.cat {
                 mc::cat_deref(b, _, mc::region_ptr(MutMutable, _)) => {
@@ -451,7 +451,7 @@ impl<'self> CheckLoanCtxt<'self> {
                         id: guarantor.id,
                         derefs: deref_count
                     };
-                    debug!("Inserting write guard at %?", key);
+                    debug2!("Inserting write guard at {:?}", key);
                     this.bccx.write_guard_map.insert(key);
                 }
 
@@ -646,11 +646,11 @@ impl<'self> CheckLoanCtxt<'self> {
                                    loan: &Loan) {
         self.bccx.span_err(
             expr.span,
-            fmt!("cannot assign to `%s` because it is borrowed",
+            format!("cannot assign to `{}` because it is borrowed",
                  self.bccx.loan_path_to_str(loan_path)));
         self.bccx.span_note(
             loan.span,
-            fmt!("borrow of `%s` occurs here",
+            format!("borrow of `{}` occurs here",
                  self.bccx.loan_path_to_str(loan_path)));
     }
 
@@ -674,12 +674,12 @@ impl<'self> CheckLoanCtxt<'self> {
                 MoveWhileBorrowed(loan_path, loan_span) => {
                     self.bccx.span_err(
                         span,
-                        fmt!("cannot move out of `%s` \
+                        format!("cannot move out of `{}` \
                               because it is borrowed",
                              self.bccx.loan_path_to_str(move_path)));
                     self.bccx.span_note(
                         loan_span,
-                        fmt!("borrow of `%s` occurs here",
+                        format!("borrow of `{}` occurs here",
                              self.bccx.loan_path_to_str(loan_path)));
                 }
             }
@@ -690,7 +690,7 @@ impl<'self> CheckLoanCtxt<'self> {
     pub fn analyze_move_out_from(&self,
                                  expr_id: ast::NodeId,
                                  move_path: @LoanPath) -> MoveError {
-        debug!("analyze_move_out_from(expr_id=%?, move_path=%s)",
+        debug2!("analyze_move_out_from(expr_id={:?}, move_path={})",
                expr_id, move_path.repr(self.tcx()));
 
         // FIXME(#4384) inadequare if/when we permit `move a.b`
@@ -772,12 +772,12 @@ fn check_loans_in_fn<'a>(this: &mut CheckLoanCtxt<'a>,
                 MoveWhileBorrowed(loan_path, loan_span) => {
                     this.bccx.span_err(
                         cap_var.span,
-                        fmt!("cannot move `%s` into closure \
+                        format!("cannot move `{}` into closure \
                               because it is borrowed",
                              this.bccx.loan_path_to_str(move_path)));
                     this.bccx.span_note(
                         loan_span,
-                        fmt!("borrow of `%s` occurs here",
+                        format!("borrow of `{}` occurs here",
                              this.bccx.loan_path_to_str(loan_path)));
                 }
             }
@@ -794,7 +794,7 @@ fn check_loans_in_expr<'a>(this: &mut CheckLoanCtxt<'a>,
                            expr: @ast::Expr) {
     visit::walk_expr(this, expr, ());
 
-    debug!("check_loans_in_expr(expr=%s)",
+    debug2!("check_loans_in_expr(expr={})",
            expr.repr(this.tcx()));
 
     this.check_for_conflicting_loans(expr.id);
@@ -805,7 +805,7 @@ fn check_loans_in_expr<'a>(this: &mut CheckLoanCtxt<'a>,
       ast::ExprPath(*) => {
           if !this.move_data.is_assignee(expr.id) {
               let cmt = this.bccx.cat_expr_unadjusted(expr);
-              debug!("path cmt=%s", cmt.repr(this.tcx()));
+              debug2!("path cmt={}", cmt.repr(this.tcx()));
               let r = opt_loan_path(cmt);
               for &lp in r.iter() {
                   this.check_if_path_is_moved(expr.id, expr.span, MovedInUse, lp);
diff --git a/src/librustc/middle/borrowck/gather_loans/gather_moves.rs b/src/librustc/middle/borrowck/gather_loans/gather_moves.rs
index 549a7fe195c..a6db028a491 100644
--- a/src/librustc/middle/borrowck/gather_loans/gather_moves.rs
+++ b/src/librustc/middle/borrowck/gather_loans/gather_moves.rs
@@ -105,7 +105,7 @@ fn check_is_legal_to_move_from(bccx: &BorrowckCtxt,
         mc::cat_deref(_, _, mc::unsafe_ptr(*)) => {
             bccx.span_err(
                 cmt0.span,
-                fmt!("cannot move out of %s",
+                format!("cannot move out of {}",
                      bccx.cmt_to_str(cmt)));
             false
         }
@@ -120,7 +120,7 @@ fn check_is_legal_to_move_from(bccx: &BorrowckCtxt,
             };
             bccx.span_err(
                 cmt0.span,
-                fmt!("cannot move out of %s%s", bccx.cmt_to_str(cmt), once_hint));
+                format!("cannot move out of {}{}", bccx.cmt_to_str(cmt), once_hint));
             false
         }
 
@@ -158,7 +158,7 @@ fn check_is_legal_to_move_from(bccx: &BorrowckCtxt,
                     if ty::has_dtor(bccx.tcx, did) {
                         bccx.span_err(
                             cmt0.span,
-                            fmt!("cannot move out of type `%s`, \
+                            format!("cannot move out of type `{}`, \
                                   which defines the `Drop` trait",
                                  b.ty.user_string(bccx.tcx)));
                         false
diff --git a/src/librustc/middle/borrowck/gather_loans/lifetime.rs b/src/librustc/middle/borrowck/gather_loans/lifetime.rs
index 2d71eef4de9..485004a642c 100644
--- a/src/librustc/middle/borrowck/gather_loans/lifetime.rs
+++ b/src/librustc/middle/borrowck/gather_loans/lifetime.rs
@@ -27,7 +27,7 @@ pub fn guarantee_lifetime(bccx: &BorrowckCtxt,
                           cmt: mc::cmt,
                           loan_region: ty::Region,
                           loan_mutbl: LoanMutability) {
-    debug!("guarantee_lifetime(cmt=%s, loan_region=%s)",
+    debug2!("guarantee_lifetime(cmt={}, loan_region={})",
            cmt.repr(bccx.tcx), loan_region.repr(bccx.tcx));
     let ctxt = GuaranteeLifetimeContext {bccx: bccx,
                                          item_scope_id: item_scope_id,
@@ -101,7 +101,7 @@ impl<'self> GuaranteeLifetimeContext<'self> {
                     // L-Deref-Managed-Mut-Compiler-Root
                     self.check_root(cmt, base, derefs, ptr_mutbl, discr_scope);
                 } else {
-                    debug!("omitting root, base=%s, base_scope=%?",
+                    debug2!("omitting root, base={}, base_scope={:?}",
                            base.repr(self.tcx()), base_scope);
                 }
             }
@@ -189,8 +189,8 @@ impl<'self> GuaranteeLifetimeContext<'self> {
                   derefs: uint,
                   ptr_mutbl: ast::Mutability,
                   discr_scope: Option<ast::NodeId>) {
-        debug!("check_root(cmt_deref=%s, cmt_base=%s, derefs=%?, ptr_mutbl=%?, \
-                discr_scope=%?)",
+        debug2!("check_root(cmt_deref={}, cmt_base={}, derefs={:?}, ptr_mutbl={:?}, \
+                discr_scope={:?})",
                cmt_deref.repr(self.tcx()),
                cmt_base.repr(self.tcx()),
                derefs,
@@ -213,7 +213,7 @@ impl<'self> GuaranteeLifetimeContext<'self> {
                 // the check above should fail for anything is not re_scope
                 self.bccx.tcx.sess.span_bug(
                     cmt_base.span,
-                    fmt!("Cannot issue root for scope region: %?",
+                    format!("Cannot issue root for scope region: {:?}",
                          self.loan_region));
             }
         };
@@ -247,7 +247,7 @@ impl<'self> GuaranteeLifetimeContext<'self> {
         // FIXME(#3511) grow to the nearest cleanup scope---this can
         // cause observable errors if freezing!
         if !self.bccx.tcx.region_maps.is_cleanup_scope(root_scope) {
-            debug!("%? is not a cleanup scope, adjusting", root_scope);
+            debug2!("{:?} is not a cleanup scope, adjusting", root_scope);
 
             let cleanup_scope =
                 self.bccx.tcx.region_maps.cleanup_scope(root_scope);
@@ -255,8 +255,8 @@ impl<'self> GuaranteeLifetimeContext<'self> {
             if opt_dyna.is_some() {
                 self.tcx().sess.span_warn(
                     self.span,
-                    fmt!("Dynamic freeze scope artifically extended \
-                          (see Issue #6248)"));
+                    format!("Dynamic freeze scope artifically extended \
+                          (see Issue \\#6248)"));
                 note_and_explain_region(
                     self.bccx.tcx,
                     "managed value only needs to be frozen for ",
@@ -277,7 +277,7 @@ impl<'self> GuaranteeLifetimeContext<'self> {
         let root_info = RootInfo {scope: root_scope, freeze: opt_dyna};
         self.bccx.root_map.insert(rm_key, root_info);
 
-        debug!("root_key: %? root_info: %?", rm_key, root_info);
+        debug2!("root_key: {:?} root_info: {:?}", rm_key, root_info);
     }
 
     fn check_scope(&self, max_scope: ty::Region) {
@@ -310,7 +310,7 @@ impl<'self> GuaranteeLifetimeContext<'self> {
             r @ mc::cat_discr(*) => {
                 self.tcx().sess.span_bug(
                     cmt.span,
-                    fmt!("illegal guarantor category: %?", r));
+                    format!("illegal guarantor category: {:?}", r));
             }
         }
     }
diff --git a/src/librustc/middle/borrowck/gather_loans/mod.rs b/src/librustc/middle/borrowck/gather_loans/mod.rs
index 4c526341446..b3980c2e045 100644
--- a/src/librustc/middle/borrowck/gather_loans/mod.rs
+++ b/src/librustc/middle/borrowck/gather_loans/mod.rs
@@ -136,7 +136,7 @@ fn gather_loans_in_fn(this: &mut GatherLoanCtxt,
                       id: ast::NodeId) {
     match fk {
         &visit::fk_item_fn(*) | &visit::fk_method(*) => {
-            fail!("cannot occur, due to visit_item override");
+            fail2!("cannot occur, due to visit_item override");
         }
 
         // Visit closures as part of the containing item.
@@ -196,7 +196,7 @@ fn gather_loans_in_expr(this: &mut GatherLoanCtxt,
     let bccx = this.bccx;
     let tcx = bccx.tcx;
 
-    debug!("gather_loans_in_expr(expr=%?/%s)",
+    debug2!("gather_loans_in_expr(expr={:?}/{})",
            ex.id, pprust::expr_to_str(ex, tcx.sess.intr()));
 
     this.id_range.add(ex.id);
@@ -330,20 +330,20 @@ impl<'self> GatherLoanCtxt<'self> {
     pub fn guarantee_adjustments(&mut self,
                                  expr: @ast::Expr,
                                  adjustment: &ty::AutoAdjustment) {
-        debug!("guarantee_adjustments(expr=%s, adjustment=%?)",
+        debug2!("guarantee_adjustments(expr={}, adjustment={:?})",
                expr.repr(self.tcx()), adjustment);
         let _i = indenter();
 
         match *adjustment {
             ty::AutoAddEnv(*) => {
-                debug!("autoaddenv -- no autoref");
+                debug2!("autoaddenv -- no autoref");
                 return;
             }
 
             ty::AutoDerefRef(
                 ty::AutoDerefRef {
                     autoref: None, _ }) => {
-                debug!("no autoref");
+                debug2!("no autoref");
                 return;
             }
 
@@ -355,7 +355,7 @@ impl<'self> GatherLoanCtxt<'self> {
                     tcx: self.tcx(),
                     method_map: self.bccx.method_map};
                 let cmt = mcx.cat_expr_autoderefd(expr, autoderefs);
-                debug!("after autoderef, cmt=%s", cmt.repr(self.tcx()));
+                debug2!("after autoderef, cmt={}", cmt.repr(self.tcx()));
 
                 match *autoref {
                     ty::AutoPtr(r, m) => {
@@ -412,8 +412,8 @@ impl<'self> GatherLoanCtxt<'self> {
                            cmt: mc::cmt,
                            req_mutbl: LoanMutability,
                            loan_region: ty::Region) {
-        debug!("guarantee_valid(borrow_id=%?, cmt=%s, \
-                req_mutbl=%?, loan_region=%?)",
+        debug2!("guarantee_valid(borrow_id={:?}, cmt={}, \
+                req_mutbl={:?}, loan_region={:?})",
                borrow_id,
                cmt.repr(self.tcx()),
                req_mutbl,
@@ -470,16 +470,16 @@ impl<'self> GatherLoanCtxt<'self> {
                     ty::re_infer(*) => {
                         self.tcx().sess.span_bug(
                             cmt.span,
-                            fmt!("Invalid borrow lifetime: %?", loan_region));
+                            format!("Invalid borrow lifetime: {:?}", loan_region));
                     }
                 };
-                debug!("loan_scope = %?", loan_scope);
+                debug2!("loan_scope = {:?}", loan_scope);
 
                 let gen_scope = self.compute_gen_scope(borrow_id, loan_scope);
-                debug!("gen_scope = %?", gen_scope);
+                debug2!("gen_scope = {:?}", gen_scope);
 
                 let kill_scope = self.compute_kill_scope(loan_scope, loan_path);
-                debug!("kill_scope = %?", kill_scope);
+                debug2!("kill_scope = {:?}", kill_scope);
 
                 if req_mutbl == MutableMutability {
                     self.mark_loan_path_as_mutated(loan_path);
@@ -499,7 +499,7 @@ impl<'self> GatherLoanCtxt<'self> {
             }
         };
 
-        debug!("guarantee_valid(borrow_id=%?), loan=%s",
+        debug2!("guarantee_valid(borrow_id={:?}), loan={}",
                borrow_id, loan.repr(self.tcx()));
 
         // let loan_path = loan.loan_path;
@@ -785,7 +785,7 @@ impl<'self> GatherLoanCtxt<'self> {
             _ => {
                 self.tcx().sess.span_bug(
                     pat.span,
-                    fmt!("Type of slice pattern is not a slice"));
+                    format!("Type of slice pattern is not a slice"));
             }
         }
     }
diff --git a/src/librustc/middle/borrowck/mod.rs b/src/librustc/middle/borrowck/mod.rs
index 8b9dc40777a..f2bfc6fb4ec 100644
--- a/src/librustc/middle/borrowck/mod.rs
+++ b/src/librustc/middle/borrowck/mod.rs
@@ -117,7 +117,7 @@ pub fn check_crate(
     fn make_stat(bccx: &mut BorrowckCtxt, stat: uint) -> ~str {
         let stat_f = stat as float;
         let total = bccx.stats.guaranteed_paths as float;
-        fmt!("%u (%.0f%%)", stat  , stat_f * 100f / total)
+        format!("{} ({:.0f}%)", stat  , stat_f * 100f / total)
     }
 }
 
@@ -135,7 +135,7 @@ fn borrowck_fn(this: &mut BorrowckCtxt,
 
         &visit::fk_item_fn(*) |
         &visit::fk_method(*) => {
-            debug!("borrowck_fn(id=%?)", id);
+            debug2!("borrowck_fn(id={:?})", id);
 
             // Check the body of fn items.
             let (id_range, all_loans, move_data) =
@@ -561,7 +561,7 @@ impl BorrowckCtxt {
             move_data::Declared => {
                 self.tcx.sess.span_err(
                     use_span,
-                    fmt!("%s of possibly uninitialized value: `%s`",
+                    format!("{} of possibly uninitialized value: `{}`",
                          verb,
                          self.loan_path_to_str(lp)));
             }
@@ -569,7 +569,7 @@ impl BorrowckCtxt {
                 let partially = if lp == moved_lp {""} else {"partially "};
                 self.tcx.sess.span_err(
                     use_span,
-                    fmt!("%s of %smoved value: `%s`",
+                    format!("{} of {}moved value: `{}`",
                          verb,
                          partially,
                          self.loan_path_to_str(lp)));
@@ -585,7 +585,7 @@ impl BorrowckCtxt {
                         "moved by default (use `copy` to override)");
                 self.tcx.sess.span_note(
                     expr.span,
-                    fmt!("`%s` moved here because it has type `%s`, which is %s",
+                    format!("`{}` moved here because it has type `{}`, which is {}",
                          self.loan_path_to_str(moved_lp),
                          expr_ty.user_string(self.tcx), suggestion));
             }
@@ -594,7 +594,7 @@ impl BorrowckCtxt {
                 let pat_ty = ty::node_id_to_type(self.tcx, pat.id);
                 self.tcx.sess.span_note(
                     pat.span,
-                    fmt!("`%s` moved here because it has type `%s`, \
+                    format!("`{}` moved here because it has type `{}`, \
                           which is moved by default (use `ref` to override)",
                          self.loan_path_to_str(moved_lp),
                          pat_ty.user_string(self.tcx)));
@@ -607,8 +607,8 @@ impl BorrowckCtxt {
                          capture that instead to override)");
                 self.tcx.sess.span_note(
                     expr.span,
-                    fmt!("`%s` moved into closure environment here because it \
-                          has type `%s`, which is %s",
+                    format!("`{}` moved into closure environment here because it \
+                          has type `{}`, which is {}",
                          self.loan_path_to_str(moved_lp),
                          expr_ty.user_string(self.tcx), suggestion));
             }
@@ -634,11 +634,11 @@ impl BorrowckCtxt {
                                                 &move_data::Assignment) {
         self.tcx.sess.span_err(
             span,
-            fmt!("re-assignment of immutable variable `%s`",
+            format!("re-assignment of immutable variable `{}`",
                  self.loan_path_to_str(lp)));
         self.tcx.sess.span_note(
             assign.span,
-            fmt!("prior assignment occurs here"));
+            format!("prior assignment occurs here"));
     }
 
     pub fn span_err(&self, s: Span, m: &str) {
@@ -652,23 +652,23 @@ impl BorrowckCtxt {
     pub fn bckerr_to_str(&self, err: BckError) -> ~str {
         match err.code {
             err_mutbl(lk) => {
-                fmt!("cannot borrow %s %s as %s",
+                format!("cannot borrow {} {} as {}",
                      err.cmt.mutbl.to_user_str(),
                      self.cmt_to_str(err.cmt),
                      self.mut_to_str(lk))
             }
             err_out_of_root_scope(*) => {
-                fmt!("cannot root managed value long enough")
+                format!("cannot root managed value long enough")
             }
             err_out_of_scope(*) => {
-                fmt!("borrowed value does not live long enough")
+                format!("borrowed value does not live long enough")
             }
             err_freeze_aliasable_const => {
                 // Means that the user borrowed a ~T or enum value
                 // residing in &const or @const pointer.  Terrible
                 // error message, but then &const and @const are
                 // supposed to be going away.
-                fmt!("unsafe borrow of aliasable, const value")
+                format!("unsafe borrow of aliasable, const value")
             }
         }
     }
@@ -686,19 +686,19 @@ impl BorrowckCtxt {
             mc::AliasableOther => {
                 self.tcx.sess.span_err(
                     span,
-                    fmt!("%s in an aliasable location", prefix));
+                    format!("{} in an aliasable location", prefix));
             }
             mc::AliasableManaged(ast::MutMutable) => {
                 // FIXME(#6269) reborrow @mut to &mut
                 self.tcx.sess.span_err(
                     span,
-                    fmt!("%s in a `@mut` pointer; \
+                    format!("{} in a `@mut` pointer; \
                           try borrowing as `&mut` first", prefix));
             }
             mc::AliasableManaged(m) => {
                 self.tcx.sess.span_err(
                     span,
-                    fmt!("%s in a `@%s` pointer; \
+                    format!("{} in a `@{}` pointer; \
                           try an `@mut` instead",
                          prefix,
                          self.mut_to_keyword(m)));
@@ -706,7 +706,7 @@ impl BorrowckCtxt {
             mc::AliasableBorrowed(m) => {
                 self.tcx.sess.span_err(
                     span,
-                    fmt!("%s in a `&%s` pointer; \
+                    format!("{} in a `&{}` pointer; \
                           try an `&mut` instead",
                          prefix,
                          self.mut_to_keyword(m)));
@@ -774,7 +774,7 @@ impl BorrowckCtxt {
                     }
                     r => {
                         self.tcx.sess.bug(
-                            fmt!("Loan path LpVar(%?) maps to %?, not local",
+                            format!("Loan path LpVar({:?}) maps to {:?}, not local",
                                  id, r));
                     }
                 }
@@ -849,7 +849,7 @@ impl DataFlowOperator for LoanDataFlowOperator {
 
 impl Repr for Loan {
     fn repr(&self, tcx: ty::ctxt) -> ~str {
-        fmt!("Loan_%?(%s, %?, %?-%?, %s)",
+        format!("Loan_{:?}({}, {:?}, {:?}-{:?}, {})",
              self.index,
              self.loan_path.repr(tcx),
              self.mutbl,
@@ -861,7 +861,7 @@ impl Repr for Loan {
 
 impl Repr for Restriction {
     fn repr(&self, tcx: ty::ctxt) -> ~str {
-        fmt!("Restriction(%s, %x)",
+        format!("Restriction({}, {:x})",
              self.loan_path.repr(tcx),
              self.set.bits as uint)
     }
@@ -871,15 +871,15 @@ impl Repr for LoanPath {
     fn repr(&self, tcx: ty::ctxt) -> ~str {
         match self {
             &LpVar(id) => {
-                fmt!("$(%?)", id)
+                format!("$({:?})", id)
             }
 
             &LpExtend(lp, _, LpDeref(_)) => {
-                fmt!("%s.*", lp.repr(tcx))
+                format!("{}.*", lp.repr(tcx))
             }
 
             &LpExtend(lp, _, LpInterior(ref interior)) => {
-                fmt!("%s.%s", lp.repr(tcx), interior.repr(tcx))
+                format!("{}.{}", lp.repr(tcx), interior.repr(tcx))
             }
         }
     }
diff --git a/src/librustc/middle/borrowck/move_data.rs b/src/librustc/middle/borrowck/move_data.rs
index d7423fddd76..239254e82dd 100644
--- a/src/librustc/middle/borrowck/move_data.rs
+++ b/src/librustc/middle/borrowck/move_data.rs
@@ -244,7 +244,7 @@ impl MoveData {
             }
         };
 
-        debug!("move_path(lp=%s, index=%?)",
+        debug2!("move_path(lp={}, index={:?})",
                lp.repr(tcx),
                index);
 
@@ -304,7 +304,7 @@ impl MoveData {
          * location `id` with kind `kind`.
          */
 
-        debug!("add_move(lp=%s, id=%?, kind=%?)",
+        debug2!("add_move(lp={}, id={:?}, kind={:?})",
                lp.repr(tcx),
                id,
                kind);
@@ -334,7 +334,7 @@ impl MoveData {
          * location `id` with the given `span`.
          */
 
-        debug!("add_assignment(lp=%s, assign_id=%?, assignee_id=%?",
+        debug2!("add_assignment(lp={}, assign_id={:?}, assignee_id={:?}",
                lp.repr(tcx), assign_id, assignee_id);
 
         let path_index = self.move_path(tcx, lp);
@@ -348,12 +348,12 @@ impl MoveData {
         };
 
         if self.is_var_path(path_index) {
-            debug!("add_assignment[var](lp=%s, assignment=%u, path_index=%?)",
+            debug2!("add_assignment[var](lp={}, assignment={}, path_index={:?})",
                    lp.repr(tcx), self.var_assignments.len(), path_index);
 
             self.var_assignments.push(assignment);
         } else {
-            debug!("add_assignment[path](lp=%s, path_index=%?)",
+            debug2!("add_assignment[path](lp={}, path_index={:?})",
                    lp.repr(tcx), path_index);
 
             self.path_assignments.push(assignment);
diff --git a/src/librustc/middle/cfg/construct.rs b/src/librustc/middle/cfg/construct.rs
index 2a224b9fd32..9e92bd3829c 100644
--- a/src/librustc/middle/cfg/construct.rs
+++ b/src/librustc/middle/cfg/construct.rs
@@ -239,7 +239,7 @@ impl CFGBuilder {
                 expr_exit
             }
 
-            ast::ExprForLoop(*) => fail!("non-desugared expr_for_loop"),
+            ast::ExprForLoop(*) => fail2!("non-desugared expr_for_loop"),
 
             ast::ExprLoop(ref body, _) => {
                 //
@@ -504,13 +504,13 @@ impl CFGBuilder {
                         }
                         self.tcx.sess.span_bug(
                             expr.span,
-                            fmt!("No loop scope for id %?", loop_id));
+                            format!("No loop scope for id {:?}", loop_id));
                     }
 
                     r => {
                         self.tcx.sess.span_bug(
                             expr.span,
-                            fmt!("Bad entry `%?` in def_map for label", r));
+                            format!("Bad entry `{:?}` in def_map for label", r));
                     }
                 }
             }
diff --git a/src/librustc/middle/check_const.rs b/src/librustc/middle/check_const.rs
index 3a50306bb87..30cf827cb72 100644
--- a/src/librustc/middle/check_const.rs
+++ b/src/librustc/middle/check_const.rs
@@ -153,7 +153,7 @@ pub fn check_expr(v: &mut CheckCrateVisitor,
               Some(&DefStruct(_)) => { }
 
               Some(&def) => {
-                debug!("(checking const) found bad def: %?", def);
+                debug2!("(checking const) found bad def: {:?}", def);
                 sess.span_err(
                     e.span,
                     "paths in constants may only refer to \
@@ -266,7 +266,7 @@ impl Visitor<()> for CheckItemRecursionVisitor {
                         ast_map::node_item(it, _) => {
                             self.visit_item(it, ());
                         }
-                        _ => fail!("const not bound to an item")
+                        _ => fail2!("const not bound to an item")
                     },
                 _ => ()
             },
diff --git a/src/librustc/middle/check_match.rs b/src/librustc/middle/check_match.rs
index a726644c15a..8befb42f300 100644
--- a/src/librustc/middle/check_match.rs
+++ b/src/librustc/middle/check_match.rs
@@ -86,8 +86,8 @@ pub fn check_expr(v: &mut CheckMatchVisitor,
        if (*arms).is_empty() {
            if !type_is_empty(cx.tcx, pat_ty) {
                // We know the type is inhabited, so this must be wrong
-               cx.tcx.sess.span_err(ex.span, fmt!("non-exhaustive patterns: \
-                            type %s is non-empty",
+               cx.tcx.sess.span_err(ex.span, format!("non-exhaustive patterns: \
+                            type {} is non-empty",
                             ty_to_str(cx.tcx, pat_ty)));
            }
            // If the type *is* empty, it's vacuously exhaustive
@@ -180,20 +180,20 @@ pub fn check_exhaustive(cx: &MatchCheckCtxt, sp: Span, pats: ~[@Pat]) {
                 ty::ty_enum(id, _) => {
                     let vid = match *ctor {
                         variant(id) => id,
-                        _ => fail!("check_exhaustive: non-variant ctor"),
+                        _ => fail2!("check_exhaustive: non-variant ctor"),
                     };
                     let variants = ty::enum_variants(cx.tcx, id);
 
                     match variants.iter().find(|v| v.id == vid) {
                         Some(v) => Some(cx.tcx.sess.str_of(v.name)),
                         None => {
-                            fail!("check_exhaustive: bad variant in ctor")
+                            fail2!("check_exhaustive: bad variant in ctor")
                         }
                     }
                 }
                 ty::ty_unboxed_vec(*) | ty::ty_evec(*) => {
                     match *ctor {
-                        vec(n) => Some(fmt!("vectors of length %u", n).to_managed()),
+                        vec(n) => Some(format!("vectors of length {}", n).to_managed()),
                         _ => None
                     }
                 }
@@ -202,7 +202,7 @@ pub fn check_exhaustive(cx: &MatchCheckCtxt, sp: Span, pats: ~[@Pat]) {
         }
     };
     let msg = ~"non-exhaustive patterns" + match ext {
-        Some(ref s) => fmt!(": %s not covered",  *s),
+        Some(ref s) => format!(": {} not covered",  *s),
         None => ~""
     };
     cx.tcx.sess.span_err(sp, msg);
@@ -408,7 +408,7 @@ pub fn missing_ctor(cx: &MatchCheckCtxt,
                     return Some(variant(v.id));
                 }
             }
-            fail!();
+            fail2!();
         } else { None }
       }
       ty::ty_nil => None,
@@ -420,7 +420,7 @@ pub fn missing_ctor(cx: &MatchCheckCtxt,
               None => (),
               Some(val(const_bool(true))) => true_found = true,
               Some(val(const_bool(false))) => false_found = true,
-              _ => fail!("impossible case")
+              _ => fail2!("impossible case")
             }
         }
         if true_found && false_found { None }
@@ -510,10 +510,10 @@ pub fn ctor_arity(cx: &MatchCheckCtxt, ctor: &ctor, ty: ty::t) -> uint {
       ty::ty_box(_) | ty::ty_uniq(_) | ty::ty_rptr(*) => 1u,
       ty::ty_enum(eid, _) => {
           let id = match *ctor { variant(id) => id,
-          _ => fail!("impossible case") };
+          _ => fail2!("impossible case") };
         match ty::enum_variants(cx.tcx, eid).iter().find(|v| v.id == id ) {
             Some(v) => v.args.len(),
-            None => fail!("impossible case")
+            None => fail2!("impossible case")
         }
       }
       ty::ty_struct(cid, _) => ty::lookup_struct_fields(cx.tcx, cid).len(),
@@ -584,7 +584,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                                 }
                             }
                             single => true,
-                            _ => fail!("type error")
+                            _ => fail2!("type error")
                         };
                         if match_ {
                             Some(r.tail().to_owned())
@@ -631,7 +631,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                                 }
                             }
                             single => true,
-                            _ => fail!("type error")
+                            _ => fail2!("type error")
                         };
                         if match_ {
                             Some(r.tail().to_owned())
@@ -693,7 +693,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                             _ => {
                                 cx.tcx.sess.span_bug(
                                     pat_span,
-                                    fmt!("struct pattern resolved to %s, \
+                                    format!("struct pattern resolved to {}, \
                                           not a struct",
                                          ty_to_str(cx.tcx, left_ty)));
                             }
@@ -739,7 +739,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                         }
                     }
                     single => true,
-                    _ => fail!("type error")
+                    _ => fail2!("type error")
                 };
                 if match_ { Some(r.tail().to_owned()) } else { None }
             }
@@ -748,7 +748,7 @@ pub fn specialize(cx: &MatchCheckCtxt,
                     val(ref v) => (*v, *v),
                     range(ref lo, ref hi) => (*lo, *hi),
                     single => return Some(r.tail().to_owned()),
-                    _ => fail!("type error")
+                    _ => fail2!("type error")
                 };
                 let v_lo = eval_const_expr(cx.tcx, lo);
                 let v_hi = eval_const_expr(cx.tcx, hi);
@@ -929,8 +929,8 @@ pub fn check_legality_of_move_bindings(cx: &MatchCheckCtxt,
                     _ => {
                         cx.tcx.sess.span_bug(
                             p.span,
-                            fmt!("Binding pattern %d is \
-                                  not an identifier: %?",
+                            format!("Binding pattern {} is \
+                                  not an identifier: {:?}",
                                  p.id, p.node));
                     }
                 }
diff --git a/src/librustc/middle/dataflow.rs b/src/librustc/middle/dataflow.rs
index 0e4d2bcd910..b9355d32663 100644
--- a/src/librustc/middle/dataflow.rs
+++ b/src/librustc/middle/dataflow.rs
@@ -103,20 +103,20 @@ impl<O:DataFlowOperator> pprust::pp_ann for DataFlowContext<O> {
 
             let gens = self.gens.slice(start, end);
             let gens_str = if gens.iter().any(|&u| u != 0) {
-                fmt!(" gen: %s", bits_to_str(gens))
+                format!(" gen: {}", bits_to_str(gens))
             } else {
                 ~""
             };
 
             let kills = self.kills.slice(start, end);
             let kills_str = if kills.iter().any(|&u| u != 0) {
-                fmt!(" kill: %s", bits_to_str(kills))
+                format!(" kill: {}", bits_to_str(kills))
             } else {
                 ~""
             };
 
-            let comment_str = fmt!("id %d: %s%s%s",
-                                   id, entry_str, gens_str, kills_str);
+            let comment_str = format!("id {}: {}{}{}",
+                                      id, entry_str, gens_str, kills_str);
             pprust::synth_comment(ps, comment_str);
             pp::space(ps.s);
         }
@@ -131,7 +131,7 @@ impl<O:DataFlowOperator> DataFlowContext<O> {
                bits_per_id: uint) -> DataFlowContext<O> {
         let words_per_id = (bits_per_id + uint::bits - 1) / uint::bits;
 
-        debug!("DataFlowContext::new(id_range=%?, bits_per_id=%?, words_per_id=%?)",
+        debug2!("DataFlowContext::new(id_range={:?}, bits_per_id={:?}, words_per_id={:?})",
                id_range, bits_per_id, words_per_id);
 
         let gens = ~[];
@@ -154,7 +154,7 @@ impl<O:DataFlowOperator> DataFlowContext<O> {
     pub fn add_gen(&mut self, id: ast::NodeId, bit: uint) {
         //! Indicates that `id` generates `bit`
 
-        debug!("add_gen(id=%?, bit=%?)", id, bit);
+        debug2!("add_gen(id={:?}, bit={:?})", id, bit);
         let (start, end) = self.compute_id_range(id);
         {
             let gens = self.gens.mut_slice(start, end);
@@ -165,7 +165,7 @@ impl<O:DataFlowOperator> DataFlowContext<O> {
     pub fn add_kill(&mut self, id: ast::NodeId, bit: uint) {
         //! Indicates that `id` kills `bit`
 
-        debug!("add_kill(id=%?, bit=%?)", id, bit);
+        debug2!("add_kill(id={:?}, bit={:?})", id, bit);
         let (start, end) = self.compute_id_range(id);
         {
             let kills = self.kills.mut_slice(start, end);
@@ -176,7 +176,7 @@ impl<O:DataFlowOperator> DataFlowContext<O> {
     fn apply_gen_kill(&mut self, id: ast::NodeId, bits: &mut [uint]) {
         //! Applies the gen and kill sets for `id` to `bits`
 
-        debug!("apply_gen_kill(id=%?, bits=%s) [before]",
+        debug2!("apply_gen_kill(id={:?}, bits={}) [before]",
                id, mut_bits_to_str(bits));
         let (start, end) = self.compute_id_range(id);
         let gens = self.gens.slice(start, end);
@@ -184,17 +184,17 @@ impl<O:DataFlowOperator> DataFlowContext<O> {
         let kills = self.kills.slice(start, end);
         bitwise(bits, kills, |a, b| a & !b);
 
-        debug!("apply_gen_kill(id=%?, bits=%s) [after]",
+        debug2!("apply_gen_kill(id={:?}, bits={}) [after]",
                id, mut_bits_to_str(bits));
     }
 
     fn apply_kill(&mut self, id: ast::NodeId, bits: &mut [uint]) {
-        debug!("apply_kill(id=%?, bits=%s) [before]",
+        debug2!("apply_kill(id={:?}, bits={}) [before]",
                id, mut_bits_to_str(bits));
         let (start, end) = self.compute_id_range(id);
         let kills = self.kills.slice(start, end);
         bitwise(bits, kills, |a, b| a & !b);
-        debug!("apply_kill(id=%?, bits=%s) [after]",
+        debug2!("apply_kill(id={:?}, bits={}) [after]",
                id, mut_bits_to_str(bits));
     }
 
@@ -242,7 +242,7 @@ impl<O:DataFlowOperator> DataFlowContext<O> {
         }
         let (start, end) = self.compute_id_range_frozen(id);
         let on_entry = self.on_entry.slice(start, end);
-        debug!("each_bit_on_entry_frozen(id=%?, on_entry=%s)",
+        debug2!("each_bit_on_entry_frozen(id={:?}, on_entry={})",
                id, bits_to_str(on_entry));
         self.each_bit(on_entry, f)
     }
@@ -255,7 +255,7 @@ impl<O:DataFlowOperator> DataFlowContext<O> {
 
         let (start, end) = self.compute_id_range(id);
         let on_entry = self.on_entry.slice(start, end);
-        debug!("each_bit_on_entry(id=%?, on_entry=%s)",
+        debug2!("each_bit_on_entry(id={:?}, on_entry={})",
                id, bits_to_str(on_entry));
         self.each_bit(on_entry, f)
     }
@@ -267,7 +267,7 @@ impl<O:DataFlowOperator> DataFlowContext<O> {
 
         let (start, end) = self.compute_id_range(id);
         let gens = self.gens.slice(start, end);
-        debug!("each_gen_bit(id=%?, gens=%s)",
+        debug2!("each_gen_bit(id={:?}, gens={})",
                id, bits_to_str(gens));
         self.each_bit(gens, f)
     }
@@ -281,7 +281,7 @@ impl<O:DataFlowOperator> DataFlowContext<O> {
         }
         let (start, end) = self.compute_id_range_frozen(id);
         let gens = self.gens.slice(start, end);
-        debug!("each_gen_bit(id=%?, gens=%s)",
+        debug2!("each_gen_bit(id={:?}, gens={})",
                id, bits_to_str(gens));
         self.each_bit(gens, f)
     }
@@ -346,8 +346,8 @@ impl<O:DataFlowOperator+Clone+'static> DataFlowContext<O> {
             }
         }
 
-        debug!("Dataflow result:");
-        debug!("%s", {
+        debug2!("Dataflow result:");
+        debug2!("{}", {
             let this = @(*self).clone();
             this.pretty_print_to(io::stderr(), blk);
             ""
@@ -374,7 +374,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
                   blk: &ast::Block,
                   in_out: &mut [uint],
                   loop_scopes: &mut ~[LoopScope]) {
-        debug!("DataFlowContext::walk_block(blk.id=%?, in_out=%s)",
+        debug2!("DataFlowContext::walk_block(blk.id={:?}, in_out={})",
                blk.id, bits_to_str(reslice(in_out)));
 
         self.merge_with_entry_set(blk.id, in_out);
@@ -425,7 +425,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
                  expr: &ast::Expr,
                  in_out: &mut [uint],
                  loop_scopes: &mut ~[LoopScope]) {
-        debug!("DataFlowContext::walk_expr(expr=%s, in_out=%s)",
+        debug2!("DataFlowContext::walk_expr(expr={}, in_out={})",
                expr.repr(self.dfcx.tcx), bits_to_str(reslice(in_out)));
 
         self.merge_with_entry_set(expr.id, in_out);
@@ -569,7 +569,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
                 copy_bits(new_loop_scope.break_bits, in_out);
             }
 
-            ast::ExprForLoop(*) => fail!("non-desugared expr_for_loop"),
+            ast::ExprForLoop(*) => fail2!("non-desugared expr_for_loop"),
 
             ast::ExprLoop(ref blk, _) => {
                 //
@@ -756,7 +756,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
         let tcx = self.tcx();
         let region_maps = tcx.region_maps;
 
-        debug!("pop_scopes(from_expr=%s, to_scope=%?, in_out=%s)",
+        debug2!("pop_scopes(from_expr={}, to_scope={:?}, in_out={})",
                from_expr.repr(tcx), to_scope.loop_id,
                bits_to_str(reslice(in_out)));
 
@@ -769,7 +769,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
                 None => {
                     tcx.sess.span_bug(
                         from_expr.span,
-                        fmt!("pop_scopes(from_expr=%s, to_scope=%?) \
+                        format!("pop_scopes(from_expr={}, to_scope={:?}) \
                               to_scope does not enclose from_expr",
                              from_expr.repr(tcx), to_scope.loop_id));
                 }
@@ -784,7 +784,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
         self.pop_scopes(from_expr, to_scope, in_out);
         self.dfcx.apply_kill(from_expr.id, in_out);
         join_bits(&self.dfcx.oper, reslice(in_out), to_scope.break_bits);
-        debug!("break_from_to(from_expr=%s, to_scope=%?) final break_bits=%s",
+        debug2!("break_from_to(from_expr={}, to_scope={:?}) final break_bits={}",
                from_expr.repr(self.tcx()),
                to_scope.loop_id,
                bits_to_str(reslice(in_out)));
@@ -833,11 +833,11 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
                 pat: @ast::Pat,
                 in_out: &mut [uint],
                 _loop_scopes: &mut ~[LoopScope]) {
-        debug!("DataFlowContext::walk_pat(pat=%s, in_out=%s)",
+        debug2!("DataFlowContext::walk_pat(pat={}, in_out={})",
                pat.repr(self.dfcx.tcx), bits_to_str(reslice(in_out)));
 
         do ast_util::walk_pat(pat) |p| {
-            debug!("  p.id=%? in_out=%s", p.id, bits_to_str(reslice(in_out)));
+            debug2!("  p.id={:?} in_out={}", p.id, bits_to_str(reslice(in_out)));
             self.merge_with_entry_set(p.id, in_out);
             self.dfcx.apply_gen_kill(p.id, in_out);
             true
@@ -882,7 +882,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
                             None => {
                                 self.tcx().sess.span_bug(
                                     expr.span,
-                                    fmt!("No loop scope for id %?", loop_id));
+                                    format!("No loop scope for id {:?}", loop_id));
                             }
                         }
                     }
@@ -890,7 +890,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
                     r => {
                         self.tcx().sess.span_bug(
                             expr.span,
-                            fmt!("Bad entry `%?` in def_map for label", r));
+                            format!("Bad entry `{:?}` in def_map for label", r));
                     }
                 }
             }
@@ -909,7 +909,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
     }
 
     fn add_to_entry_set(&mut self, id: ast::NodeId, pred_bits: &[uint]) {
-        debug!("add_to_entry_set(id=%?, pred_bits=%s)",
+        debug2!("add_to_entry_set(id={:?}, pred_bits={})",
                id, bits_to_str(pred_bits));
         let (start, end) = self.dfcx.compute_id_range(id);
         let changed = { // FIXME(#5074) awkward construction
@@ -917,7 +917,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
             join_bits(&self.dfcx.oper, pred_bits, on_entry)
         };
         if changed {
-            debug!("changed entry set for %? to %s",
+            debug2!("changed entry set for {:?} to {}",
                    id, bits_to_str(self.dfcx.on_entry.slice(start, end)));
             self.changed = true;
         }
@@ -926,7 +926,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
     fn merge_with_entry_set(&mut self,
                             id: ast::NodeId,
                             pred_bits: &mut [uint]) {
-        debug!("merge_with_entry_set(id=%?, pred_bits=%s)",
+        debug2!("merge_with_entry_set(id={:?}, pred_bits={})",
                id, mut_bits_to_str(pred_bits));
         let (start, end) = self.dfcx.compute_id_range(id);
         let changed = { // FIXME(#5074) awkward construction
@@ -936,7 +936,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
             changed
         };
         if changed {
-            debug!("changed entry set for %? to %s",
+            debug2!("changed entry set for {:?} to {}",
                    id, bits_to_str(self.dfcx.on_entry.slice(start, end)));
             self.changed = true;
         }
@@ -957,7 +957,7 @@ fn bits_to_str(words: &[uint]) -> ~str {
         let mut v = word;
         for _ in range(0u, uint::bytes) {
             result.push_char(sep);
-            result.push_str(fmt!("%02x", v & 0xFF));
+            result.push_str(format!("{:02x}", v & 0xFF));
             v >>= 8;
             sep = '-';
         }
@@ -992,12 +992,12 @@ fn bitwise(out_vec: &mut [uint],
 }
 
 fn set_bit(words: &mut [uint], bit: uint) -> bool {
-    debug!("set_bit: words=%s bit=%s",
+    debug2!("set_bit: words={} bit={}",
            mut_bits_to_str(words), bit_str(bit));
     let word = bit / uint::bits;
     let bit_in_word = bit % uint::bits;
     let bit_mask = 1 << bit_in_word;
-    debug!("word=%u bit_in_word=%u bit_mask=%u", word, bit_in_word, word);
+    debug2!("word={} bit_in_word={} bit_mask={}", word, bit_in_word, word);
     let oldv = words[word];
     let newv = oldv | bit_mask;
     words[word] = newv;
@@ -1007,7 +1007,7 @@ fn set_bit(words: &mut [uint], bit: uint) -> bool {
 fn bit_str(bit: uint) -> ~str {
     let byte = bit >> 8;
     let lobits = 1 << (bit & 0xFF);
-    fmt!("[%u:%u-%02x]", bit, byte, lobits)
+    format!("[{}:{}-{:02x}]", bit, byte, lobits)
 }
 
 fn reslice<'a>(v: &'a mut [uint]) -> &'a [uint] {
diff --git a/src/librustc/middle/effect.rs b/src/librustc/middle/effect.rs
index 9c02f544fba..6d479ca220a 100644
--- a/src/librustc/middle/effect.rs
+++ b/src/librustc/middle/effect.rs
@@ -58,12 +58,12 @@ impl EffectCheckVisitor {
             SafeContext => {
                 // Report an error.
                 self.tcx.sess.span_err(span,
-                                  fmt!("%s requires unsafe function or block",
+                                  format!("{} requires unsafe function or block",
                                        description))
             }
             UnsafeBlock(block_id) => {
                 // OK, but record this.
-                debug!("effect: recording unsafe block as used: %?", block_id);
+                debug2!("effect: recording unsafe block as used: {:?}", block_id);
                 let _ = self.tcx.used_unsafe.insert(block_id);
             }
             UnsafeFn => {}
@@ -119,7 +119,7 @@ impl Visitor<()> for EffectCheckVisitor {
             match expr.node {
                 ExprMethodCall(callee_id, _, _, _, _, _) => {
                     let base_type = ty::node_id_to_type(self.tcx, callee_id);
-                    debug!("effect: method call case, base type is %s",
+                    debug2!("effect: method call case, base type is {}",
                            ppaux::ty_to_str(self.tcx, base_type));
                     if type_is_unsafe_function(base_type) {
                         self.require_unsafe(expr.span,
@@ -128,7 +128,7 @@ impl Visitor<()> for EffectCheckVisitor {
                 }
                 ExprCall(base, _, _) => {
                     let base_type = ty::node_id_to_type(self.tcx, base.id);
-                    debug!("effect: call case, base type is %s",
+                    debug2!("effect: call case, base type is {}",
                            ppaux::ty_to_str(self.tcx, base_type));
                     if type_is_unsafe_function(base_type) {
                         self.require_unsafe(expr.span, "call to unsafe function")
@@ -136,7 +136,7 @@ impl Visitor<()> for EffectCheckVisitor {
                 }
                 ExprUnary(_, UnDeref, base) => {
                     let base_type = ty::node_id_to_type(self.tcx, base.id);
-                    debug!("effect: unary case, base type is %s",
+                    debug2!("effect: unary case, base type is {}",
                            ppaux::ty_to_str(self.tcx, base_type));
                     match ty::get(base_type).sty {
                         ty_ptr(_) => {
diff --git a/src/librustc/middle/freevars.rs b/src/librustc/middle/freevars.rs
index ea6ff90634a..383c37952d7 100644
--- a/src/librustc/middle/freevars.rs
+++ b/src/librustc/middle/freevars.rs
@@ -53,7 +53,7 @@ impl Visitor<int> for CollectFreevarsVisitor {
               ast::ExprPath(*) | ast::ExprSelf => {
                   let mut i = 0;
                   match self.def_map.find(&expr.id) {
-                    None => fail!("path not found"),
+                    None => fail2!("path not found"),
                     Some(&df) => {
                       let mut def = df;
                       while i < depth {
@@ -137,7 +137,7 @@ pub fn annotate_freevars(def_map: resolve::DefMap, crate: &ast::Crate) ->
 
 pub fn get_freevars(tcx: ty::ctxt, fid: ast::NodeId) -> freevar_info {
     match tcx.freevars.find(&fid) {
-      None => fail!("get_freevars: %d has no freevars", fid),
+      None => fail2!("get_freevars: {} has no freevars", fid),
       Some(&d) => return d
     }
 }
diff --git a/src/librustc/middle/graph.rs b/src/librustc/middle/graph.rs
index 46394454d00..98912b57572 100644
--- a/src/librustc/middle/graph.rs
+++ b/src/librustc/middle/graph.rs
@@ -343,7 +343,7 @@ mod test {
         do graph.each_incoming_edge(start_index) |edge_index, edge| {
             assert_eq!(graph.edge_data(edge_index), &edge.data);
             assert!(counter < expected_incoming.len());
-            debug!("counter=%? expected=%? edge_index=%? edge=%?",
+            debug2!("counter={:?} expected={:?} edge_index={:?} edge={:?}",
                    counter, expected_incoming[counter], edge_index, edge);
             match expected_incoming[counter] {
                 (ref e, ref n) => {
@@ -361,7 +361,7 @@ mod test {
         do graph.each_outgoing_edge(start_index) |edge_index, edge| {
             assert_eq!(graph.edge_data(edge_index), &edge.data);
             assert!(counter < expected_outgoing.len());
-            debug!("counter=%? expected=%? edge_index=%? edge=%?",
+            debug2!("counter={:?} expected={:?} edge_index={:?} edge={:?}",
                    counter, expected_outgoing[counter], edge_index, edge);
             match expected_outgoing[counter] {
                 (ref e, ref n) => {
diff --git a/src/librustc/middle/kind.rs b/src/librustc/middle/kind.rs
index 270babb9cf3..b20cb8ed809 100644
--- a/src/librustc/middle/kind.rs
+++ b/src/librustc/middle/kind.rs
@@ -124,13 +124,13 @@ fn check_impl_of_trait(cx: &mut Context, it: @item, trait_ref: &trait_ref, self_
 
     // If this trait has builtin-kind supertraits, meet them.
     let self_ty: ty::t = ty::node_id_to_type(cx.tcx, it.id);
-    debug!("checking impl with self type %?", ty::get(self_ty).sty);
+    debug2!("checking impl with self type {:?}", ty::get(self_ty).sty);
     do check_builtin_bounds(cx, self_ty, trait_def.bounds) |missing| {
         cx.tcx.sess.span_err(self_type.span,
-            fmt!("the type `%s', which does not fulfill `%s`, cannot implement this \
+            format!("the type `{}', which does not fulfill `{}`, cannot implement this \
                   trait", ty_to_str(cx.tcx, self_ty), missing.user_string(cx.tcx)));
         cx.tcx.sess.span_note(self_type.span,
-            fmt!("types implementing this trait must fulfill `%s`",
+            format!("types implementing this trait must fulfill `{}`",
                  trait_def.bounds.user_string(cx.tcx)));
     }
 
@@ -238,7 +238,7 @@ fn with_appropriate_checker(cx: &Context, id: NodeId,
         }
         ref s => {
             cx.tcx.sess.bug(
-                fmt!("expect fn type in kind checker, not %?", s));
+                format!("expect fn type in kind checker, not {:?}", s));
         }
     }
 }
@@ -265,7 +265,7 @@ fn check_fn(
 }
 
 pub fn check_expr(cx: &mut Context, e: @Expr) {
-    debug!("kind::check_expr(%s)", expr_to_str(e, cx.tcx.sess.intr()));
+    debug2!("kind::check_expr({})", expr_to_str(e, cx.tcx.sess.intr()));
 
     // Handle any kind bounds on type parameters
     let type_parameter_id = match e.get_callee_id() {
@@ -292,9 +292,9 @@ pub fn check_expr(cx: &mut Context, e: @Expr) {
             };
             if ts.len() != type_param_defs.len() {
                 // Fail earlier to make debugging easier
-                fail!("internal error: in kind::check_expr, length \
+                fail2!("internal error: in kind::check_expr, length \
                       mismatch between actual and declared bounds: actual = \
-                      %s, declared = %s",
+                      {}, declared = {}",
                       ts.repr(cx.tcx),
                       type_param_defs.repr(cx.tcx));
             }
@@ -375,8 +375,8 @@ pub fn check_typaram_bounds(cx: &Context,
     do check_builtin_bounds(cx, ty, type_param_def.bounds.builtin_bounds) |missing| {
         cx.tcx.sess.span_err(
             sp,
-            fmt!("instantiating a type parameter with an incompatible type \
-                  `%s`, which does not fulfill `%s`",
+            format!("instantiating a type parameter with an incompatible type \
+                  `{}`, which does not fulfill `{}`",
                  ty_to_str(cx.tcx, ty),
                  missing.user_string(cx.tcx)));
     }
@@ -390,17 +390,17 @@ pub fn check_freevar_bounds(cx: &Context, sp: Span, ty: ty::t,
         // Emit a less mysterious error message in this case.
         match referenced_ty {
             Some(rty) => cx.tcx.sess.span_err(sp,
-                fmt!("cannot implicitly borrow variable of type `%s` in a bounded \
-                      stack closure (implicit reference does not fulfill `%s`)",
+                format!("cannot implicitly borrow variable of type `{}` in a bounded \
+                      stack closure (implicit reference does not fulfill `{}`)",
                      ty_to_str(cx.tcx, rty), missing.user_string(cx.tcx))),
             None => cx.tcx.sess.span_err(sp,
-                fmt!("cannot capture variable of type `%s`, which does \
-                      not fulfill `%s`, in a bounded closure",
+                format!("cannot capture variable of type `{}`, which does \
+                      not fulfill `{}`, in a bounded closure",
                      ty_to_str(cx.tcx, ty), missing.user_string(cx.tcx))),
         }
         cx.tcx.sess.span_note(
             sp,
-            fmt!("this closure's environment must satisfy `%s`",
+            format!("this closure's environment must satisfy `{}`",
                  bounds.user_string(cx.tcx)));
     }
 }
@@ -409,8 +409,8 @@ pub fn check_trait_cast_bounds(cx: &Context, sp: Span, ty: ty::t,
                                bounds: ty::BuiltinBounds) {
     do check_builtin_bounds(cx, ty, bounds) |missing| {
         cx.tcx.sess.span_err(sp,
-            fmt!("cannot pack type `%s`, which does not fulfill \
-                  `%s`, as a trait bounded by %s",
+            format!("cannot pack type `{}`, which does not fulfill \
+                  `{}`, as a trait bounded by {}",
                  ty_to_str(cx.tcx, ty), missing.user_string(cx.tcx),
                  bounds.user_string(cx.tcx)));
     }
@@ -445,27 +445,27 @@ fn check_imm_free_var(cx: &Context, def: Def, sp: Span) {
         _ => {
             cx.tcx.sess.span_bug(
                 sp,
-                fmt!("unknown def for free variable: %?", def));
+                format!("unknown def for free variable: {:?}", def));
         }
     }
 }
 
 fn check_copy(cx: &Context, ty: ty::t, sp: Span, reason: &str) {
-    debug!("type_contents(%s)=%s",
+    debug2!("type_contents({})={}",
            ty_to_str(cx.tcx, ty),
            ty::type_contents(cx.tcx, ty).to_str());
     if ty::type_moves_by_default(cx.tcx, ty) {
         cx.tcx.sess.span_err(
-            sp, fmt!("copying a value of non-copyable type `%s`",
+            sp, format!("copying a value of non-copyable type `{}`",
                      ty_to_str(cx.tcx, ty)));
-        cx.tcx.sess.span_note(sp, fmt!("%s", reason));
+        cx.tcx.sess.span_note(sp, format!("{}", reason));
     }
 }
 
 pub fn check_send(cx: &Context, ty: ty::t, sp: Span) -> bool {
     if !ty::type_is_sendable(cx.tcx, ty) {
         cx.tcx.sess.span_err(
-            sp, fmt!("value has non-sendable type `%s`",
+            sp, format!("value has non-sendable type `{}`",
                      ty_to_str(cx.tcx, ty)));
         false
     } else {
@@ -565,8 +565,8 @@ pub fn check_cast_for_escaping_regions(
             // if !target_regions.iter().any(|t_r| is_subregion_of(cx, *t_r, r)) {
             //     cx.tcx.sess.span_err(
             //         source.span,
-            //         fmt!("source contains borrowed pointer with lifetime \
-            //               not found in the target type `%s`",
+            //         format!("source contains borrowed pointer with lifetime \
+            //               not found in the target type `{}`",
             //              ty_to_str(cx.tcx, target_ty)));
             //     note_and_explain_region(
             //         cx.tcx, "source data is only valid for ", r, "");
diff --git a/src/librustc/middle/lang_items.rs b/src/librustc/middle/lang_items.rs
index 92c619eba0e..f154255e7b6 100644
--- a/src/librustc/middle/lang_items.rs
+++ b/src/librustc/middle/lang_items.rs
@@ -154,7 +154,7 @@ impl LanguageItems {
     pub fn require(&self, it: LangItem) -> Result<DefId, ~str> {
         match self.items[it as uint] {
             Some(id) => Ok(id),
-            None => Err(fmt!("requires `%s` lang_item",
+            None => Err(format!("requires `{}` lang_item",
                              LanguageItems::item_name(it as uint)))
         }
     }
@@ -398,7 +398,7 @@ impl<'self> LanguageItemCollector<'self> {
         // Check for duplicates.
         match self.items.items[item_index] {
             Some(original_def_id) if original_def_id != item_def_id => {
-                self.session.err(fmt!("duplicate entry for `%s`",
+                self.session.err(format!("duplicate entry for `{}`",
                                       LanguageItems::item_name(item_index)));
             }
             Some(_) | None => {
diff --git a/src/librustc/middle/lint.rs b/src/librustc/middle/lint.rs
index 3c6ebc9311d..591ca2ada5a 100644
--- a/src/librustc/middle/lint.rs
+++ b/src/librustc/middle/lint.rs
@@ -430,7 +430,7 @@ impl Context {
                 return *k;
             }
         }
-        fail!("unregistered lint %?", lint);
+        fail2!("unregistered lint {:?}", lint);
     }
 
     fn span_lint(&self, lint: lint, span: Span, msg: &str) {
@@ -444,9 +444,9 @@ impl Context {
         let mut note = None;
         let msg = match src {
             Default | CommandLine => {
-                fmt!("%s [-%c %s%s]", msg, match level {
+                format!("{} [-{} {}{}]", msg, match level {
                         warn => 'W', deny => 'D', forbid => 'F',
-                        allow => fail!()
+                        allow => fail2!()
                     }, self.lint_to_str(lint).replace("_", "-"),
                     if src == Default { " (default)" } else { "" })
             },
@@ -458,7 +458,7 @@ impl Context {
         match level {
             warn =>          { self.tcx.sess.span_warn(span, msg); }
             deny | forbid => { self.tcx.sess.span_err(span, msg);  }
-            allow => fail!(),
+            allow => fail2!(),
         }
 
         for &span in note.iter() {
@@ -483,7 +483,7 @@ impl Context {
                     self.span_lint(
                         unrecognized_lint,
                         meta.span,
-                        fmt!("unknown `%s` attribute: `%s`",
+                        format!("unknown `{}` attribute: `{}`",
                         level_to_str(level), lintname));
                 }
                 Some(lint) => {
@@ -491,7 +491,7 @@ impl Context {
                     let now = self.get_level(lint);
                     if now == forbid && level != forbid {
                         self.tcx.sess.span_err(meta.span,
-                        fmt!("%s(%s) overruled by outer forbid(%s)",
+                        format!("{}({}) overruled by outer forbid({})",
                         level_to_str(level),
                         lintname, lintname));
                     } else if now != level {
@@ -757,7 +757,7 @@ impl TypeLimitsLintVisitor {
             ast::BiGt => v >= min,
             ast::BiGe => v > min,
             ast::BiEq | ast::BiNe => v >= min && v <= max,
-            _ => fail!()
+            _ => fail2!()
         }
     }
 
@@ -821,7 +821,7 @@ impl TypeLimitsLintVisitor {
                         ast::lit_int_unsuffixed(v) => v,
                         _ => return true
                     },
-                    _ => fail!()
+                    _ => fail2!()
                 };
                 self.is_valid(norm_binop, lit_val, min, max)
             }
@@ -834,7 +834,7 @@ impl TypeLimitsLintVisitor {
                         ast::lit_int_unsuffixed(v) => v as u64,
                         _ => return true
                     },
-                    _ => fail!()
+                    _ => fail2!()
                 };
                 self.is_valid(norm_binop, lit_val, min, max)
             }
@@ -1071,7 +1071,7 @@ fn check_item_non_camel_case_types(cx: &Context, it: &ast::item) {
         if !is_camel_case(cx.tcx, ident) {
             cx.span_lint(
                 non_camel_case_types, span,
-                fmt!("%s `%s` should have a camel case identifier",
+                format!("{} `{}` should have a camel case identifier",
                     sort, cx.tcx.sess.str_of(ident)));
         }
     }
@@ -1437,7 +1437,7 @@ impl StabilityLintVisitor {
                         None => return
                     }
                 }
-                _ => cx.tcx.sess.bug(fmt!("handle_def: %? not found", id))
+                _ => cx.tcx.sess.bug(format!("handle_def: {:?} not found", id))
             }
         } else {
             // cross-crate
@@ -1466,9 +1466,9 @@ impl StabilityLintVisitor {
 
         let msg = match stability {
             Some(attr::Stability { text: Some(ref s), _ }) => {
-                fmt!("use of %s item: %s", label, *s)
+                format!("use of {} item: {}", label, *s)
             }
-            _ => fmt!("use of %s item", label)
+            _ => format!("use of {} item", label)
         };
 
         cx.span_lint(lint, sp, msg);
@@ -1613,8 +1613,8 @@ pub fn check_crate(tcx: ty::ctxt, crate: &ast::Crate) {
         for t in v.iter() {
             match *t {
                 (lint, span, ref msg) =>
-                    tcx.sess.span_bug(span, fmt!("unprocessed lint %? at %s: \
-                                                  %s",
+                    tcx.sess.span_bug(span, format!("unprocessed lint {:?} at {}: \
+                                                  {}",
                                                  lint,
                                                  ast_map::node_id_to_str(
                                                  tcx.items,
diff --git a/src/librustc/middle/liveness.rs b/src/librustc/middle/liveness.rs
index 9e28bfcb964..e9119e75287 100644
--- a/src/librustc/middle/liveness.rs
+++ b/src/librustc/middle/liveness.rs
@@ -144,9 +144,9 @@ enum LiveNodeKind {
 fn live_node_kind_to_str(lnk: LiveNodeKind, cx: ty::ctxt) -> ~str {
     let cm = cx.sess.codemap;
     match lnk {
-        FreeVarNode(s) => fmt!("Free var node [%s]", cm.span_to_str(s)),
-        ExprNode(s)    => fmt!("Expr node [%s]", cm.span_to_str(s)),
-        VarDefNode(s)  => fmt!("Var def node [%s]", cm.span_to_str(s)),
+        FreeVarNode(s) => format!("Free var node [{}]", cm.span_to_str(s)),
+        ExprNode(s)    => format!("Expr node [{}]", cm.span_to_str(s)),
+        VarDefNode(s)  => format!("Var def node [{}]", cm.span_to_str(s)),
         ExitNode       => ~"Exit node"
     }
 }
@@ -176,11 +176,11 @@ pub fn check_crate(tcx: ty::ctxt,
 }
 
 impl to_str::ToStr for LiveNode {
-    fn to_str(&self) -> ~str { fmt!("ln(%u)", **self) }
+    fn to_str(&self) -> ~str { format!("ln({})", **self) }
 }
 
 impl to_str::ToStr for Variable {
-    fn to_str(&self) -> ~str { fmt!("v(%u)", **self) }
+    fn to_str(&self) -> ~str { format!("v({})", **self) }
 }
 
 // ______________________________________________________________________
@@ -276,7 +276,7 @@ impl IrMaps {
         self.lnks.push(lnk);
         self.num_live_nodes += 1;
 
-        debug!("%s is of kind %s", ln.to_str(),
+        debug2!("{} is of kind {}", ln.to_str(),
                live_node_kind_to_str(lnk, self.tcx));
 
         ln
@@ -288,7 +288,7 @@ impl IrMaps {
         let ln = self.add_live_node(lnk);
         self.live_node_map.insert(node_id, ln);
 
-        debug!("%s is node %d", ln.to_str(), node_id);
+        debug2!("{} is node {}", ln.to_str(), node_id);
     }
 
     pub fn add_variable(&mut self, vk: VarKind) -> Variable {
@@ -303,7 +303,7 @@ impl IrMaps {
             ImplicitRet => {}
         }
 
-        debug!("%s is %?", v.to_str(), vk);
+        debug2!("{} is {:?}", v.to_str(), vk);
 
         v
     }
@@ -313,7 +313,7 @@ impl IrMaps {
           Some(&var) => var,
           None => {
             self.tcx.sess.span_bug(
-                span, fmt!("No variable registered for id %d", node_id));
+                span, format!("No variable registered for id {}", node_id));
           }
         }
     }
@@ -367,7 +367,7 @@ fn visit_fn(v: &mut LivenessVisitor,
             sp: Span,
             id: NodeId,
             this: @mut IrMaps) {
-    debug!("visit_fn: id=%d", id);
+    debug2!("visit_fn: id={}", id);
     let _i = ::util::common::indenter();
 
     // swap in a new set of IR maps for this function body:
@@ -376,13 +376,13 @@ fn visit_fn(v: &mut LivenessVisitor,
                               this.capture_map);
 
     unsafe {
-        debug!("creating fn_maps: %x", transmute(&*fn_maps));
+        debug2!("creating fn_maps: {}", transmute::<&IrMaps, *IrMaps>(fn_maps));
     }
 
     for arg in decl.inputs.iter() {
         do pat_util::pat_bindings(this.tcx.def_map, arg.pat)
                 |_bm, arg_id, _x, path| {
-            debug!("adding argument %d", arg_id);
+            debug2!("adding argument {}", arg_id);
             let ident = ast_util::path_to_ident(path);
             fn_maps.add_variable(Arg(arg_id, ident));
         }
@@ -429,7 +429,7 @@ fn visit_fn(v: &mut LivenessVisitor,
 fn visit_local(v: &mut LivenessVisitor, local: @Local, this: @mut IrMaps) {
     let def_map = this.tcx.def_map;
     do pat_util::pat_bindings(def_map, local.pat) |_bm, p_id, sp, path| {
-        debug!("adding local variable %d", p_id);
+        debug2!("adding local variable {}", p_id);
         let name = ast_util::path_to_ident(path);
         this.add_live_node_for_node(p_id, VarDefNode(sp));
         let kind = match local.init {
@@ -450,7 +450,7 @@ fn visit_arm(v: &mut LivenessVisitor, arm: &Arm, this: @mut IrMaps) {
     let def_map = this.tcx.def_map;
     for pat in arm.pats.iter() {
         do pat_util::pat_bindings(def_map, *pat) |bm, p_id, sp, path| {
-            debug!("adding local variable %d from match with bm %?",
+            debug2!("adding local variable {} from match with bm {:?}",
                    p_id, bm);
             let name = ast_util::path_to_ident(path);
             this.add_live_node_for_node(p_id, VarDefNode(sp));
@@ -470,7 +470,7 @@ fn visit_expr(v: &mut LivenessVisitor, expr: @Expr, this: @mut IrMaps) {
       // live nodes required for uses or definitions of variables:
       ExprPath(_) | ExprSelf => {
         let def = this.tcx.def_map.get_copy(&expr.id);
-        debug!("expr %d: path that leads to %?", expr.id, def);
+        debug2!("expr {}: path that leads to {:?}", expr.id, def);
         if moves::moved_variable_node_id_from_def(def).is_some() {
             this.add_live_node_for_node(expr.id, ExprNode(expr.span));
         }
@@ -515,7 +515,7 @@ fn visit_expr(v: &mut LivenessVisitor, expr: @Expr, this: @mut IrMaps) {
         this.add_live_node_for_node(expr.id, ExprNode(expr.span));
         visit::walk_expr(v, expr, this);
       }
-      ExprForLoop(*) => fail!("non-desugared expr_for_loop"),
+      ExprForLoop(*) => fail2!("non-desugared expr_for_loop"),
       ExprBinary(_, op, _, _) if ast_util::lazy_binop(op) => {
         this.add_live_node_for_node(expr.id, ExprNode(expr.span));
         visit::walk_expr(v, expr, this);
@@ -609,7 +609,7 @@ impl Liveness {
             // code have to agree about which AST nodes are worth
             // creating liveness nodes for.
             self.tcx.sess.span_bug(
-                span, fmt!("No live node registered for node %d",
+                span, format!("No live node registered for node {}",
                            node_id));
           }
         }
@@ -788,7 +788,7 @@ impl Liveness {
             wr.write_str("[ln(");
             wr.write_uint(*ln);
             wr.write_str(") of kind ");
-            wr.write_str(fmt!("%?", self.ir.lnks[*ln]));
+            wr.write_str(format!("{:?}", self.ir.lnks[*ln]));
             wr.write_str(" reads");
             self.write_vars(wr, ln, |idx| self.users[idx].reader );
             wr.write_str("  writes");
@@ -819,7 +819,7 @@ impl Liveness {
         self.indices2(ln, succ_ln, |idx, succ_idx| {
             self.users[idx] = self.users[succ_idx]
         });
-        debug!("init_from_succ(ln=%s, succ=%s)",
+        debug2!("init_from_succ(ln={}, succ={})",
                self.ln_str(ln), self.ln_str(succ_ln));
     }
 
@@ -843,7 +843,7 @@ impl Liveness {
             }
         }
 
-        debug!("merge_from_succ(ln=%s, succ=%s, first_merge=%b, changed=%b)",
+        debug2!("merge_from_succ(ln={}, succ={}, first_merge={}, changed={})",
                ln.to_str(), self.ln_str(succ_ln), first_merge, changed);
         return changed;
 
@@ -866,7 +866,7 @@ impl Liveness {
         self.users[idx].reader = invalid_node();
         self.users[idx].writer = invalid_node();
 
-        debug!("%s defines %s (idx=%u): %s", writer.to_str(), var.to_str(),
+        debug2!("{} defines {} (idx={}): {}", writer.to_str(), var.to_str(),
                idx, self.ln_str(writer));
     }
 
@@ -891,7 +891,7 @@ impl Liveness {
             user.used = true;
         }
 
-        debug!("%s accesses[%x] %s: %s",
+        debug2!("{} accesses[{:x}] {}: {}",
                ln.to_str(), acc, var.to_str(), self.ln_str(ln));
     }
 
@@ -902,18 +902,18 @@ impl Liveness {
         // effectively a return---this only occurs in `for` loops,
         // where the body is really a closure.
 
-        debug!("compute: using id for block, %s", block_to_str(body,
+        debug2!("compute: using id for block, {}", block_to_str(body,
                       self.tcx.sess.intr()));
 
         let entry_ln: LiveNode =
             self.with_loop_nodes(body.id, self.s.exit_ln, self.s.exit_ln,
               || { self.propagate_through_fn_block(decl, body) });
 
-        // hack to skip the loop unless debug! is enabled:
-        debug!("^^ liveness computation results for body %d (entry=%s)",
+        // hack to skip the loop unless debug2! is enabled:
+        debug2!("^^ liveness computation results for body {} (entry={})",
                {
                    for ln_idx in range(0u, self.ir.num_live_nodes) {
-                       debug!("%s", self.ln_str(LiveNode(ln_idx)));
+                       debug2!("{}", self.ln_str(LiveNode(ln_idx)));
                    }
                    body.id
                },
@@ -1007,7 +1007,7 @@ impl Liveness {
 
     pub fn propagate_through_expr(&self, expr: @Expr, succ: LiveNode)
                                   -> LiveNode {
-        debug!("propagate_through_expr: %s",
+        debug2!("propagate_through_expr: {}",
              expr_to_str(expr, self.tcx.sess.intr()));
 
         match expr.node {
@@ -1022,7 +1022,7 @@ impl Liveness {
           }
 
           ExprFnBlock(_, ref blk) => {
-              debug!("%s is an expr_fn_block",
+              debug2!("{} is an expr_fn_block",
                    expr_to_str(expr, self.tcx.sess.intr()));
 
               /*
@@ -1070,7 +1070,7 @@ impl Liveness {
             self.propagate_through_loop(expr, Some(cond), blk, succ)
           }
 
-          ExprForLoop(*) => fail!("non-desugared expr_for_loop"),
+          ExprForLoop(*) => fail2!("non-desugared expr_for_loop"),
 
           // Note that labels have been resolved, so we don't need to look
           // at the label ident
@@ -1379,7 +1379,7 @@ impl Liveness {
             self.merge_from_succ(ln, succ, first_merge);
             first_merge = false;
         }
-        debug!("propagate_through_loop: using id for loop body %d %s",
+        debug2!("propagate_through_loop: using id for loop body {} {}",
                expr.id, block_to_str(body, self.tcx.sess.intr()));
 
         let cond_ln = self.propagate_through_opt_expr(cond, ln);
@@ -1407,7 +1407,7 @@ impl Liveness {
                               cont_ln: LiveNode,
                               f: &fn() -> R)
                               -> R {
-      debug!("with_loop_nodes: %d %u", loop_node_id, *break_ln);
+      debug2!("with_loop_nodes: {} {}", loop_node_id, *break_ln);
         self.loop_scope.push(loop_node_id);
         self.break_ln.insert(loop_node_id, break_ln);
         self.cont_ln.insert(loop_node_id, cont_ln);
@@ -1430,7 +1430,7 @@ fn check_local(this: &mut Liveness, local: @Local) {
         // No initializer: the variable might be unused; if not, it
         // should not be live at this point.
 
-        debug!("check_local() with no initializer");
+        debug2!("check_local() with no initializer");
         do this.pat_bindings(local.pat) |ln, var, sp, id| {
             if !this.warn_about_unused(sp, id, ln, var) {
                 match this.live_on_exit(ln, var) {
@@ -1501,7 +1501,7 @@ fn check_expr(this: &mut Liveness, expr: @Expr) {
       ExprParen(*) | ExprFnBlock(*) | ExprPath(*) | ExprSelf(*) => {
         visit::walk_expr(this, expr, ());
       }
-      ExprForLoop(*) => fail!("non-desugared expr_for_loop")
+      ExprForLoop(*) => fail2!("non-desugared expr_for_loop")
     }
 }
 
@@ -1596,17 +1596,17 @@ impl Liveness {
           FreeVarNode(span) => {
             self.tcx.sess.span_err(
                 span,
-                fmt!("capture of %s: `%s`", msg, name));
+                format!("capture of {}: `{}`", msg, name));
           }
           ExprNode(span) => {
             self.tcx.sess.span_err(
                 span,
-                fmt!("use of %s: `%s`", msg, name));
+                format!("use of {}: `{}`", msg, name));
           }
           ExitNode | VarDefNode(_) => {
             self.tcx.sess.span_bug(
                 chk_span,
-                fmt!("illegal reader: %?", lnk));
+                format!("illegal reader: {:?}", lnk));
           }
         }
     }
@@ -1655,11 +1655,11 @@ impl Liveness {
 
                 if is_assigned {
                     self.tcx.sess.add_lint(unused_variable, id, sp,
-                        fmt!("variable `%s` is assigned to, \
+                        format!("variable `{}` is assigned to, \
                                   but never used", *name));
                 } else {
                     self.tcx.sess.add_lint(unused_variable, id, sp,
-                        fmt!("unused variable: `%s`", *name));
+                        format!("unused variable: `{}`", *name));
                 }
             }
             true
@@ -1677,7 +1677,7 @@ impl Liveness {
             let r = self.should_warn(var);
             for name in r.iter() {
                 self.tcx.sess.add_lint(dead_assignment, id, sp,
-                    fmt!("value assigned to `%s` is never read", *name));
+                    format!("value assigned to `{}` is never read", *name));
             }
         }
     }
diff --git a/src/librustc/middle/mem_categorization.rs b/src/librustc/middle/mem_categorization.rs
index 9cc95b873d2..19be4d041ed 100644
--- a/src/librustc/middle/mem_categorization.rs
+++ b/src/librustc/middle/mem_categorization.rs
@@ -214,7 +214,7 @@ pub fn deref_kind(tcx: ty::ctxt, t: ty::t) -> deref_kind {
       Some(k) => k,
       None => {
         tcx.sess.bug(
-            fmt!("deref_cat() invoked on non-derefable type %s",
+            format!("deref_cat() invoked on non-derefable type {}",
                  ty_to_str(tcx, t)));
       }
     }
@@ -288,7 +288,7 @@ pub struct mem_categorization_ctxt {
 
 impl ToStr for MutabilityCategory {
     fn to_str(&self) -> ~str {
-        fmt!("%?", *self)
+        format!("{:?}", *self)
     }
 }
 
@@ -383,7 +383,7 @@ impl mem_categorization_ctxt {
     }
 
     pub fn cat_expr_unadjusted(&self, expr: @ast::Expr) -> cmt {
-        debug!("cat_expr: id=%d expr=%s",
+        debug2!("cat_expr: id={} expr={}",
                expr.id, pprust::expr_to_str(expr, self.tcx.sess.intr()));
 
         let expr_ty = self.expr_ty(expr);
@@ -436,7 +436,7 @@ impl mem_categorization_ctxt {
             return self.cat_rvalue_node(expr, expr_ty);
           }
 
-          ast::ExprForLoop(*) => fail!("non-desugared expr_for_loop")
+          ast::ExprForLoop(*) => fail2!("non-desugared expr_for_loop")
         }
     }
 
@@ -544,7 +544,7 @@ impl mem_categorization_ctxt {
                   _ => {
                       self.tcx.sess.span_bug(
                           span,
-                          fmt!("Upvar of non-closure %? - %s",
+                          format!("Upvar of non-closure {:?} - {}",
                                fn_node_id, ty.repr(self.tcx)));
                   }
               }
@@ -651,7 +651,7 @@ impl mem_categorization_ctxt {
             None => {
                 self.tcx.sess.span_bug(
                     node.span(),
-                    fmt!("Explicit deref of non-derefable type: %s",
+                    format!("Explicit deref of non-derefable type: {}",
                          ty_to_str(self.tcx, base_cmt.ty)));
             }
         };
@@ -741,7 +741,7 @@ impl mem_categorization_ctxt {
           None => {
             self.tcx.sess.span_bug(
                 elt.span(),
-                fmt!("Explicit index of non-index type `%s`",
+                format!("Explicit index of non-index type `{}`",
                      ty_to_str(self.tcx, base_cmt.ty)));
           }
         };
@@ -872,7 +872,7 @@ impl mem_categorization_ctxt {
         // get the type of the *subpattern* and use that.
 
         let tcx = self.tcx;
-        debug!("cat_pattern: id=%d pat=%s cmt=%s",
+        debug2!("cat_pattern: id={} pat={} cmt={}",
                pat.id, pprust::pat_to_str(pat, tcx.sess.intr()),
                cmt.repr(tcx));
         let _i = indenter();
@@ -1020,7 +1020,7 @@ impl mem_categorization_ctxt {
               ~"argument"
           }
           cat_deref(_, _, pk) => {
-              fmt!("dereference of %s pointer", ptr_sigil(pk))
+              format!("dereference of {} pointer", ptr_sigil(pk))
           }
           cat_interior(_, InteriorField(NamedField(_))) => {
               ~"field"
@@ -1177,7 +1177,7 @@ impl cmt_ {
 
 impl Repr for cmt_ {
     fn repr(&self, tcx: ty::ctxt) -> ~str {
-        fmt!("{%s id:%d m:%? ty:%s}",
+        format!("\\{{} id:{} m:{:?} ty:{}\\}",
              self.cat.repr(tcx),
              self.id,
              self.mutbl,
@@ -1194,19 +1194,19 @@ impl Repr for categorization {
             cat_local(*) |
             cat_self(*) |
             cat_arg(*) => {
-                fmt!("%?", *self)
+                format!("{:?}", *self)
             }
             cat_deref(cmt, derefs, ptr) => {
-                fmt!("%s->(%s, %u)", cmt.cat.repr(tcx),
+                format!("{}->({}, {})", cmt.cat.repr(tcx),
                      ptr_sigil(ptr), derefs)
             }
             cat_interior(cmt, interior) => {
-                fmt!("%s.%s",
+                format!("{}.{}",
                      cmt.cat.repr(tcx),
                      interior.repr(tcx))
             }
             cat_downcast(cmt) => {
-                fmt!("%s->(enum)", cmt.cat.repr(tcx))
+                format!("{}->(enum)", cmt.cat.repr(tcx))
             }
             cat_stack_upvar(cmt) |
             cat_discr(cmt, _) => {
@@ -1229,7 +1229,7 @@ impl Repr for InteriorKind {
     fn repr(&self, _tcx: ty::ctxt) -> ~str {
         match *self {
             InteriorField(NamedField(fld)) => token::interner_get(fld).to_owned(),
-            InteriorField(PositionalField(i)) => fmt!("#%?", i),
+            InteriorField(PositionalField(i)) => format!("\\#{:?}", i),
             InteriorElement(_) => ~"[]",
         }
     }
diff --git a/src/librustc/middle/moves.rs b/src/librustc/middle/moves.rs
index b7bdb9a1e5d..71d0621fc16 100644
--- a/src/librustc/middle/moves.rs
+++ b/src/librustc/middle/moves.rs
@@ -275,7 +275,7 @@ impl VisitContext {
          * meaning either copied or moved depending on its type.
          */
 
-        debug!("consume_expr(expr=%s)",
+        debug2!("consume_expr(expr={})",
                expr.repr(self.tcx));
 
         let expr_ty = ty::expr_ty_adjusted(self.tcx, expr);
@@ -293,7 +293,7 @@ impl VisitContext {
          * meaning either copied or moved depending on its type.
          */
 
-        debug!("consume_block(blk.id=%?)", blk.id);
+        debug2!("consume_block(blk.id={:?})", blk.id);
 
         for stmt in blk.stmts.iter() {
             self.visit_stmt(*stmt, ());
@@ -312,7 +312,7 @@ impl VisitContext {
          * in turn trigger calls to the subcomponents of `expr`.
          */
 
-        debug!("use_expr(expr=%s, mode=%?)",
+        debug2!("use_expr(expr={}, mode={:?})",
                expr.repr(self.tcx),
                expr_mode);
 
@@ -326,7 +326,7 @@ impl VisitContext {
             _ => expr_mode
         };
 
-        debug!("comp_mode = %?", comp_mode);
+        debug2!("comp_mode = {:?}", comp_mode);
 
         match expr.node {
             ExprPath(*) | ExprSelf => {
@@ -375,7 +375,7 @@ impl VisitContext {
                     ty::ty_bare_fn(*) => Read,
                     ref x =>
                         self.tcx.sess.span_bug(callee.span,
-                            fmt!("non-function type in moves for expr_call: %?", x)),
+                            format!("non-function type in moves for expr_call: {:?}", x)),
                 };
                 // Note we're not using consume_expr, which uses type_moves_by_default
                 // to determine the mode, for this. The reason is that while stack
@@ -411,7 +411,7 @@ impl VisitContext {
                         ref r => {
                            self.tcx.sess.span_bug(
                                 with_expr.span,
-                                fmt!("bad base expr type in record: %?", r))
+                                format!("bad base expr type in record: {:?}", r))
                         }
                     };
 
@@ -435,7 +435,7 @@ impl VisitContext {
                     if consume_with {
                         if has_dtor(self.tcx, with_ty) {
                             self.tcx.sess.span_err(with_expr.span,
-                                                   fmt!("cannot move out of type `%s`, \
+                                                   format!("cannot move out of type `{}`, \
                                                          which defines the `Drop` trait",
                                                         with_ty.user_string(self.tcx)));
                         }
@@ -500,7 +500,7 @@ impl VisitContext {
                 self.consume_block(blk);
             }
 
-            ExprForLoop(*) => fail!("non-desugared expr_for_loop"),
+            ExprForLoop(*) => fail2!("non-desugared expr_for_loop"),
 
             ExprUnary(_, _, lhs) => {
                 if !self.use_overloaded_operator(expr, lhs, [])
@@ -620,7 +620,7 @@ impl VisitContext {
                 BindByRef(_) => false,
                 BindInfer => {
                     let pat_ty = ty::node_id_to_type(self.tcx, id);
-                    debug!("pattern %? %s type is %s",
+                    debug2!("pattern {:?} {} type is {}",
                            id,
                            ast_util::path_to_ident(path).repr(self.tcx),
                            pat_ty.repr(self.tcx));
@@ -628,7 +628,7 @@ impl VisitContext {
                 }
             };
 
-            debug!("pattern binding %?: bm=%?, binding_moves=%b",
+            debug2!("pattern binding {:?}: bm={:?}, binding_moves={}",
                    id, bm, binding_moves);
 
             if binding_moves {
@@ -678,7 +678,7 @@ impl VisitContext {
     }
 
     pub fn compute_captures(&mut self, fn_expr_id: NodeId) -> @[CaptureVar] {
-        debug!("compute_capture_vars(fn_expr_id=%?)", fn_expr_id);
+        debug2!("compute_capture_vars(fn_expr_id={:?})", fn_expr_id);
         let _indenter = indenter();
 
         let fn_ty = ty::node_id_to_type(self.tcx, fn_expr_id);
@@ -696,7 +696,7 @@ impl VisitContext {
                 let fvar = &freevars[i];
                 let fvar_def_id = ast_util::def_id_of_def(fvar.def).node;
                 let fvar_ty = ty::node_id_to_type(self.tcx, fvar_def_id);
-                debug!("fvar_def_id=%? fvar_ty=%s",
+                debug2!("fvar_def_id={:?} fvar_ty={}",
                        fvar_def_id, ppaux::ty_to_str(self.tcx, fvar_ty));
                 let mode = if ty::type_moves_by_default(self.tcx, fvar_ty) {
                     CapMove
diff --git a/src/librustc/middle/privacy.rs b/src/librustc/middle/privacy.rs
index 3c60bd67362..8b2e581836b 100644
--- a/src/librustc/middle/privacy.rs
+++ b/src/librustc/middle/privacy.rs
@@ -111,8 +111,8 @@ impl PrivacyVisitor {
             // WRONG
             Public
         };
-        debug!("parental_privacy = %?", parental_privacy);
-        debug!("vis = %?, priv = %?",
+        debug2!("parental_privacy = {:?}", parental_privacy);
+        debug2!("vis = {:?}, priv = {:?}",
                variant_info.vis,
                visibility_to_privacy(variant_info.vis))
         // inherited => privacy of the enum item
@@ -175,7 +175,7 @@ impl PrivacyVisitor {
             }
             Some(_) => {
                 self.tcx.sess.span_bug(span,
-                                  fmt!("method_is_private: method was a %s?!",
+                                  format!("method_is_private: method was a {}?!",
                                        ast_map::node_id_to_str(
                                             self.tcx.items,
                                             method_id,
@@ -205,8 +205,8 @@ impl PrivacyVisitor {
                 Some(&node_trait_method(_, trait_did, _)) => f(trait_did.node),
                 Some(_) => {
                     self.tcx.sess.span_bug(span,
-                                      fmt!("local_item_is_private: item was \
-                                            a %s?!",
+                                      format!("local_item_is_private: item was \
+                                            a {}?!",
                                            ast_map::node_id_to_str(
                                                 self.tcx.items,
                                                 item_id,
@@ -227,7 +227,7 @@ impl PrivacyVisitor {
         for field in fields.iter() {
             if field.name != ident.name { loop; }
             if field.vis == private {
-                self.tcx.sess.span_err(span, fmt!("field `%s` is private",
+                self.tcx.sess.span_err(span, format!("field `{}` is private",
                                              token::ident_to_str(&ident)));
             }
             break;
@@ -248,7 +248,7 @@ impl PrivacyVisitor {
                     (container_id.crate != LOCAL_CRATE ||
                      !self.privileged_items.iter().any(|x| x == &(container_id.node))) {
                 self.tcx.sess.span_err(span,
-                                  fmt!("method `%s` is private",
+                                  format!("method `{}` is private",
                                        token::ident_to_str(name)));
             }
         } else {
@@ -256,7 +256,7 @@ impl PrivacyVisitor {
                 csearch::get_item_visibility(self.tcx.sess.cstore, method_id);
             if visibility != public {
                 self.tcx.sess.span_err(span,
-                                  fmt!("method `%s` is private",
+                                  format!("method `{}` is private",
                                        token::ident_to_str(name)));
             }
         }
@@ -264,10 +264,10 @@ impl PrivacyVisitor {
 
     // Checks that a private path is in scope.
     fn check_path(&mut self, span: Span, def: Def, path: &Path) {
-        debug!("checking path");
+        debug2!("checking path");
         match def {
             DefStaticMethod(method_id, _, _) => {
-                debug!("found static method def, checking it");
+                debug2!("found static method def, checking it");
                 self.check_method_common(span,
                                          method_id,
                                          &path.segments.last().identifier)
@@ -277,7 +277,7 @@ impl PrivacyVisitor {
                     if self.local_item_is_private(span, def_id.node) &&
                             !self.privileged_items.iter().any(|x| x == &def_id.node) {
                         self.tcx.sess.span_err(span,
-                                          fmt!("function `%s` is private",
+                                          format!("function `{}` is private",
                                                token::ident_to_str(
                                                 &path.segments
                                                      .last()
@@ -286,7 +286,7 @@ impl PrivacyVisitor {
                 //} else if csearch::get_item_visibility(self.tcx.sess.cstore,
                 //                                       def_id) != public {
                 //    self.tcx.sess.span_err(span,
-                //                      fmt!("function `%s` is private",
+                //                      format!("function `{}` is private",
                 //                           token::ident_to_str(
                 //                                &path.segments
                 //                                     .last()
@@ -333,7 +333,7 @@ impl PrivacyVisitor {
                                              !self.privileged_items.iter()
                                              .any(|x| x == &(trait_id.node)) => {
                                             self.tcx.sess.span_err(span,
-                                                              fmt!("method `%s` is private",
+                                                              format!("method `{}` is private",
                                                                    token::ident_to_str(&method
                                                                                         .ident)));
                                         }
@@ -476,7 +476,7 @@ impl<'self> Visitor<Context<'self>> for PrivacyVisitor {
                         ty_struct(id, _)
                         if id.crate != LOCAL_CRATE || !self.privileged_items.iter()
                                 .any(|x| x == &(id.node)) => {
-                            debug!("(privacy checking) checking field access");
+                            debug2!("(privacy checking) checking field access");
                             self.check_field(expr.span, id, ident);
                         }
                         _ => {}
@@ -497,7 +497,7 @@ impl<'self> Visitor<Context<'self>> for PrivacyVisitor {
                                                        method map");
                                 }
                                 Some(ref entry) => {
-                                    debug!("(privacy checking) checking \
+                                    debug2!("(privacy checking) checking \
                                             impl method");
                                     self.check_method(expr.span, &entry.origin, ident);
                                 }
@@ -515,7 +515,7 @@ impl<'self> Visitor<Context<'self>> for PrivacyVisitor {
                             if id.crate != LOCAL_CRATE ||
                                     !self.privileged_items.iter().any(|x| x == &(id.node)) {
                                 for field in (*fields).iter() {
-                                        debug!("(privacy checking) checking \
+                                        debug2!("(privacy checking) checking \
                                                 field in struct literal");
                                     self.check_field(expr.span, id, field.ident);
                                 }
@@ -527,7 +527,7 @@ impl<'self> Visitor<Context<'self>> for PrivacyVisitor {
                                 match self.tcx.def_map.get_copy(&expr.id) {
                                     DefVariant(_, variant_id, _) => {
                                         for field in (*fields).iter() {
-                                                debug!("(privacy checking) \
+                                                debug2!("(privacy checking) \
                                                         checking field in \
                                                         struct variant \
                                                         literal");
@@ -582,7 +582,7 @@ impl<'self> Visitor<Context<'self>> for PrivacyVisitor {
                             if id.crate != LOCAL_CRATE ||
                                     !self.privileged_items.iter().any(|x| x == &(id.node)) {
                                 for field in fields.iter() {
-                                        debug!("(privacy checking) checking \
+                                        debug2!("(privacy checking) checking \
                                                 struct pattern");
                                     self.check_field(pattern.span, id, field.ident);
                                 }
@@ -594,7 +594,7 @@ impl<'self> Visitor<Context<'self>> for PrivacyVisitor {
                                 match self.tcx.def_map.find(&pattern.id) {
                                     Some(&DefVariant(_, variant_id, _)) => {
                                         for field in fields.iter() {
-                                            debug!("(privacy checking) \
+                                            debug2!("(privacy checking) \
                                                     checking field in \
                                                     struct variant pattern");
                                             self.check_field(pattern.span, variant_id, field.ident);
diff --git a/src/librustc/middle/reachable.rs b/src/librustc/middle/reachable.rs
index 718f8005b74..6973b46c92c 100644
--- a/src/librustc/middle/reachable.rs
+++ b/src/librustc/middle/reachable.rs
@@ -400,14 +400,14 @@ impl ReachableContext {
                     let desc = ast_map::node_id_to_str(self.tcx.items,
                                                        search_item,
                                                        ident_interner);
-                    self.tcx.sess.bug(fmt!("found unexpected thingy in \
-                                            worklist: %s",
-                                            desc))
+                    self.tcx.sess.bug(format!("found unexpected thingy in \
+                                               worklist: {}",
+                                               desc))
                 }
                 None => {
-                    self.tcx.sess.bug(fmt!("found unmapped ID in worklist: \
-                                            %d",
-                                           search_item))
+                    self.tcx.sess.bug(format!("found unmapped ID in worklist: \
+                                               {}",
+                                              search_item))
                 }
             }
         }
diff --git a/src/librustc/middle/region.rs b/src/librustc/middle/region.rs
index 5b6bb3a7b75..0afcf87817a 100644
--- a/src/librustc/middle/region.rs
+++ b/src/librustc/middle/region.rs
@@ -93,13 +93,13 @@ impl RegionMaps {
             None => {}
         }
 
-        debug!("relate_free_regions(sub=%?, sup=%?)", sub, sup);
+        debug2!("relate_free_regions(sub={:?}, sup={:?})", sub, sup);
 
         self.free_region_map.insert(sub, ~[sup]);
     }
 
     pub fn record_parent(&mut self, sub: ast::NodeId, sup: ast::NodeId) {
-        debug!("record_parent(sub=%?, sup=%?)", sub, sup);
+        debug2!("record_parent(sub={:?}, sup={:?})", sub, sup);
         assert!(sub != sup);
 
         self.scope_map.insert(sub, sup);
@@ -125,7 +125,7 @@ impl RegionMaps {
 
         match self.scope_map.find(&id) {
             Some(&r) => r,
-            None => { fail!("No enclosing scope for id %?", id); }
+            None => { fail2!("No enclosing scope for id {:?}", id); }
         }
     }
 
@@ -168,7 +168,7 @@ impl RegionMaps {
         while superscope != s {
             match self.scope_map.find(&s) {
                 None => {
-                    debug!("is_subscope_of(%?, %?, s=%?)=false",
+                    debug2!("is_subscope_of({:?}, {:?}, s={:?})=false",
                            subscope, superscope, s);
 
                     return false;
@@ -177,7 +177,7 @@ impl RegionMaps {
             }
         }
 
-        debug!("is_subscope_of(%?, %?)=true",
+        debug2!("is_subscope_of({:?}, {:?})=true",
                subscope, superscope);
 
         return true;
@@ -231,7 +231,7 @@ impl RegionMaps {
          * duplicated with the code in infer.rs.
          */
 
-        debug!("is_subregion_of(sub_region=%?, super_region=%?)",
+        debug2!("is_subregion_of(sub_region={:?}, super_region={:?})",
                sub_region, super_region);
 
         sub_region == super_region || {
@@ -303,7 +303,7 @@ impl RegionMaps {
         fn ancestors_of(this: &RegionMaps, scope: ast::NodeId)
             -> ~[ast::NodeId]
         {
-            // debug!("ancestors_of(scope=%d)", scope);
+            // debug2!("ancestors_of(scope={})", scope);
             let mut result = ~[scope];
             let mut scope = scope;
             loop {
@@ -314,7 +314,7 @@ impl RegionMaps {
                         scope = superscope;
                     }
                 }
-                // debug!("ancestors_of_loop(scope=%d)", scope);
+                // debug2!("ancestors_of_loop(scope={})", scope);
             }
         }
     }
@@ -323,7 +323,7 @@ impl RegionMaps {
 /// Records the current parent (if any) as the parent of `child_id`.
 fn parent_to_expr(visitor: &mut RegionResolutionVisitor,
                   cx: Context, child_id: ast::NodeId, sp: Span) {
-    debug!("region::parent_to_expr(span=%?)",
+    debug2!("region::parent_to_expr(span={:?})",
            visitor.sess.codemap.span_to_str(sp));
     for parent_id in cx.parent.iter() {
         visitor.region_maps.record_parent(child_id, *parent_id);
@@ -437,10 +437,10 @@ fn resolve_fn(visitor: &mut RegionResolutionVisitor,
               sp: Span,
               id: ast::NodeId,
               cx: Context) {
-    debug!("region::resolve_fn(id=%?, \
-                               span=%?, \
-                               body.id=%?, \
-                               cx.parent=%?)",
+    debug2!("region::resolve_fn(id={:?}, \
+                               span={:?}, \
+                               body.id={:?}, \
+                               cx.parent={:?})",
            id,
            visitor.sess.codemap.span_to_str(sp),
            body.id,
@@ -619,7 +619,7 @@ impl DetermineRpCtxt {
           Some(v) => join_variance(v, variance)
         };
 
-        debug!("add_rp() variance for %s: %? == %? ^ %?",
+        debug2!("add_rp() variance for {}: {:?} == {:?} ^ {:?}",
                ast_map::node_id_to_str(self.ast_map, id,
                                        token::get_ident_interner()),
                joined_variance, old_variance, variance);
@@ -637,7 +637,7 @@ impl DetermineRpCtxt {
     /// contains a value of type `from`, so if `from` is
     /// region-parameterized, so is the current item.
     pub fn add_dep(&mut self, from: ast::NodeId) {
-        debug!("add dependency from %d -> %d (%s -> %s) with variance %?",
+        debug2!("add dependency from {} -> {} ({} -> {}) with variance {:?}",
                from, self.item_id,
                ast_map::node_id_to_str(self.ast_map, from,
                                        token::get_ident_interner()),
@@ -715,7 +715,7 @@ impl DetermineRpCtxt {
         let old_anon_implies_rp = self.anon_implies_rp;
         self.item_id = item_id;
         self.anon_implies_rp = anon_implies_rp;
-        debug!("with_item_id(%d, %b)",
+        debug2!("with_item_id({}, {})",
                item_id,
                anon_implies_rp);
         let _i = ::util::common::indenter();
@@ -787,7 +787,7 @@ fn determine_rp_in_ty(visitor: &mut DetermineRpVisitor,
     let sess = cx.sess;
     match ty.node {
         ast::ty_rptr(ref r, _) => {
-            debug!("referenced rptr type %s",
+            debug2!("referenced rptr type {}",
                    pprust::ty_to_str(ty, sess.intr()));
 
             if cx.region_is_relevant(r) {
@@ -797,7 +797,7 @@ fn determine_rp_in_ty(visitor: &mut DetermineRpVisitor,
         }
 
         ast::ty_closure(ref f) => {
-            debug!("referenced fn type: %s",
+            debug2!("referenced fn type: {}",
                    pprust::ty_to_str(ty, sess.intr()));
             match f.region {
                 Some(_) => {
@@ -837,7 +837,7 @@ fn determine_rp_in_ty(visitor: &mut DetermineRpVisitor,
                 match csearch::get_region_param(cstore, did) {
                   None => {}
                   Some(variance) => {
-                    debug!("reference to external, rp'd type %s",
+                    debug2!("reference to external, rp'd type {}",
                            pprust::ty_to_str(ty, sess.intr()));
                     if cx.region_is_relevant(&path.segments.last().lifetime) {
                         let rv = cx.add_variance(variance);
@@ -967,7 +967,7 @@ pub fn determine_rp_in_crate(sess: Session,
         while cx.worklist.len() != 0 {
             let c_id = cx.worklist.pop();
             let c_variance = cx.region_paramd_items.get_copy(&c_id);
-            debug!("popped %d from worklist", c_id);
+            debug2!("popped {} from worklist", c_id);
             match cx.dep_map.find(&c_id) {
               None => {}
               Some(deps) => {
@@ -980,11 +980,11 @@ pub fn determine_rp_in_crate(sess: Session,
         }
     }
 
-    debug!("%s", {
-        debug!("Region variance results:");
+    debug2!("{}", {
+        debug2!("Region variance results:");
         let region_paramd_items = cx.region_paramd_items;
         for (&key, &value) in region_paramd_items.iter() {
-            debug!("item %? (%s) is parameterized with variance %?",
+            debug2!("item {:?} ({}) is parameterized with variance {:?}",
                    key,
                    ast_map::node_id_to_str(ast_map, key,
                                            token::get_ident_interner()),
diff --git a/src/librustc/middle/resolve.rs b/src/librustc/middle/resolve.rs
index f0ce22d5f33..4b5141f1630 100644
--- a/src/librustc/middle/resolve.rs
+++ b/src/librustc/middle/resolve.rs
@@ -646,7 +646,7 @@ impl NameBindings {
     pub fn get_module(&mut self) -> @mut Module {
         match self.get_module_if_available() {
             None => {
-                fail!("get_module called on a node with no module \
+                fail2!("get_module called on a node with no module \
                        definition!")
             }
             Some(module_def) => module_def
@@ -1096,14 +1096,14 @@ impl Resolver {
                     // had the duplicate.
                     let ns = ns.unwrap();
                     self.resolve_error(sp,
-                        fmt!("duplicate definition of %s `%s`",
+                        format!("duplicate definition of {} `{}`",
                              namespace_error_to_str(duplicate_type),
                              self.session.str_of(name)));
                     {
                         let r = child.span_for_namespace(ns);
                         for sp in r.iter() {
                             self.session.span_note(*sp,
-                                 fmt!("first definition of %s `%s` here",
+                                 format!("first definition of {} `{}` here",
                                       namespace_error_to_str(duplicate_type),
                                       self.session.str_of(name)));
                         }
@@ -1427,7 +1427,7 @@ impl Resolver {
                     }
                     match self.method_map.find_mut(name) {
                         Some(s) => { s.insert(def_id); },
-                        _ => fail!("Can't happen"),
+                        _ => fail2!("Can't happen"),
                     }
                 }
 
@@ -1436,7 +1436,7 @@ impl Resolver {
             }
 
             item_mac(*) => {
-                fail!("item macros unimplemented")
+                fail2!("item macros unimplemented")
             }
         }
     }
@@ -1620,8 +1620,8 @@ impl Resolver {
         if self.block_needs_anonymous_module(block) {
             let block_id = block.id;
 
-            debug!("(building reduced graph for block) creating a new \
-                    anonymous module for block %d",
+            debug2!("(building reduced graph for block) creating a new \
+                    anonymous module for block {}",
                    block_id);
 
             let parent_module = self.get_module_from_parent(parent);
@@ -1645,22 +1645,22 @@ impl Resolver {
                            ident: Ident,
                            new_parent: ReducedGraphParent) {
         let privacy = visibility_to_privacy(visibility);
-        debug!("(building reduced graph for \
-                external crate) building external def, priv %?",
+        debug2!("(building reduced graph for \
+                external crate) building external def, priv {:?}",
                privacy);
         match def {
           DefMod(def_id) | DefForeignMod(def_id) | DefStruct(def_id) |
           DefTy(def_id) => {
             match child_name_bindings.type_def {
               Some(TypeNsDef { module_def: Some(module_def), _ }) => {
-                debug!("(building reduced graph for external crate) \
+                debug2!("(building reduced graph for external crate) \
                         already created module");
                 module_def.def_id = Some(def_id);
               }
               Some(_) | None => {
-                debug!("(building reduced graph for \
+                debug2!("(building reduced graph for \
                         external crate) building module \
-                        %s", final_ident);
+                        {}", final_ident);
                 let parent_link = self.get_parent_link(new_parent, ident);
 
                 child_name_bindings.define_module(privacy,
@@ -1678,8 +1678,8 @@ impl Resolver {
         match def {
           DefMod(_) | DefForeignMod(_) => {}
           DefVariant(_, variant_id, is_struct) => {
-            debug!("(building reduced graph for external crate) building \
-                    variant %s",
+            debug2!("(building reduced graph for external crate) building \
+                    variant {}",
                    final_ident);
             // We assume the parent is visible, or else we wouldn't have seen
             // it.
@@ -1693,13 +1693,13 @@ impl Resolver {
             }
           }
           DefFn(*) | DefStaticMethod(*) | DefStatic(*) => {
-            debug!("(building reduced graph for external \
-                    crate) building value (fn/static) %s", final_ident);
+            debug2!("(building reduced graph for external \
+                    crate) building value (fn/static) {}", final_ident);
             child_name_bindings.define_value(privacy, def, dummy_sp());
           }
           DefTrait(def_id) => {
-              debug!("(building reduced graph for external \
-                      crate) building type %s", final_ident);
+              debug2!("(building reduced graph for external \
+                      crate) building type {}", final_ident);
 
               // If this is a trait, add all the method names
               // to the trait info.
@@ -1712,9 +1712,9 @@ impl Resolver {
                       get_method_name_and_explicit_self(self.session.cstore,
                                                         method_def_id);
 
-                  debug!("(building reduced graph for \
+                  debug2!("(building reduced graph for \
                           external crate) ... adding \
-                          trait method '%s'",
+                          trait method '{}'",
                          self.session.str_of(method_name));
 
                   // Add it to the trait info if not static.
@@ -1728,7 +1728,7 @@ impl Resolver {
                   }
                   match self.method_map.find_mut(name) {
                       Some(s) => { s.insert(def_id); },
-                      _ => fail!("Can't happen"),
+                      _ => fail2!("Can't happen"),
                   }
               }
 
@@ -1744,14 +1744,14 @@ impl Resolver {
                                                   dummy_sp())
           }
           DefTy(_) => {
-              debug!("(building reduced graph for external \
-                      crate) building type %s", final_ident);
+              debug2!("(building reduced graph for external \
+                      crate) building type {}", final_ident);
 
               child_name_bindings.define_type(privacy, def, dummy_sp());
           }
           DefStruct(def_id) => {
-            debug!("(building reduced graph for external \
-                    crate) building type and value for %s",
+            debug2!("(building reduced graph for external \
+                    crate) building type and value for {}",
                    final_ident);
             child_name_bindings.define_type(privacy, def, dummy_sp());
             if get_struct_fields(self.session.cstore, def_id).len() == 0 {
@@ -1766,7 +1766,7 @@ impl Resolver {
           DefPrimTy(*) | DefTyParam(*) | DefBinding(*) |
           DefUse(*) | DefUpvar(*) | DefRegion(*) |
           DefTyParamBinder(*) | DefLabel(*) | DefSelfTy(*) => {
-            fail!("didn't expect `%?`", def);
+            fail2!("didn't expect `{:?}`", def);
           }
         }
     }
@@ -1821,9 +1821,9 @@ impl Resolver {
                         match static_methods_opt {
                             Some(ref static_methods) if
                                 static_methods.len() >= 1 => {
-                                debug!("(building reduced graph for \
+                                debug2!("(building reduced graph for \
                                         external crate) processing \
-                                        static methods for type name %s",
+                                        static methods for type name {}",
                                         self.session.str_of(
                                             final_ident));
 
@@ -1873,9 +1873,9 @@ impl Resolver {
                                 for static_method_info in
                                         static_methods.iter() {
                                     let ident = static_method_info.ident;
-                                    debug!("(building reduced graph for \
+                                    debug2!("(building reduced graph for \
                                              external crate) creating \
-                                             static method '%s'",
+                                             static method '{}'",
                                            self.session.str_of(ident));
 
                                     let (method_name_bindings, _) =
@@ -1901,7 +1901,7 @@ impl Resolver {
                 }
             }
             DlField => {
-                debug!("(building reduced graph for external crate) \
+                debug2!("(building reduced graph for external crate) \
                         ignoring field");
             }
         }
@@ -1909,12 +1909,12 @@ impl Resolver {
 
     /// Builds the reduced graph rooted at the given external module.
     fn populate_external_module(&mut self, module: @mut Module) {
-        debug!("(populating external module) attempting to populate %s",
+        debug2!("(populating external module) attempting to populate {}",
                self.module_to_str(module));
 
         let def_id = match module.def_id {
             None => {
-                debug!("(populating external module) ... no def ID!");
+                debug2!("(populating external module) ... no def ID!");
                 return
             }
             Some(def_id) => def_id,
@@ -1922,7 +1922,7 @@ impl Resolver {
 
         do csearch::each_child_of_item(self.session.cstore, def_id)
                 |def_like, child_ident, visibility| {
-            debug!("(populating external module) ... found ident: %s",
+            debug2!("(populating external module) ... found ident: {}",
                    token::ident_to_str(&child_ident));
             self.build_reduced_graph_for_external_crate_def(module,
                                                             def_like,
@@ -1972,15 +1972,15 @@ impl Resolver {
 
         match *subclass {
             SingleImport(target, _) => {
-                debug!("(building import directive) building import \
-                        directive: privacy %? %s::%s",
+                debug2!("(building import directive) building import \
+                        directive: privacy {:?} {}::{}",
                        privacy,
                        self.idents_to_str(directive.module_path),
                        self.session.str_of(target));
 
                 match module_.import_resolutions.find(&target.name) {
                     Some(&resolution) => {
-                        debug!("(building import directive) bumping \
+                        debug2!("(building import directive) bumping \
                                 reference");
                         resolution.outstanding_references += 1;
 
@@ -1990,7 +1990,7 @@ impl Resolver {
                         resolution.value_id = id;
                     }
                     None => {
-                        debug!("(building import directive) creating new");
+                        debug2!("(building import directive) creating new");
                         let resolution = @mut ImportResolution::new(privacy, id);
                         resolution.outstanding_references = 1;
                         module_.import_resolutions.insert(target.name, resolution);
@@ -2022,14 +2022,14 @@ impl Resolver {
         let mut i = 0;
         let mut prev_unresolved_imports = 0;
         loop {
-            debug!("(resolving imports) iteration %u, %u imports left",
+            debug2!("(resolving imports) iteration {}, {} imports left",
                    i, self.unresolved_imports);
 
             let module_root = self.graph_root.get_module();
             self.resolve_imports_for_module_subtree(module_root);
 
             if self.unresolved_imports == 0 {
-                debug!("(resolving imports) success");
+                debug2!("(resolving imports) success");
                 break;
             }
 
@@ -2047,7 +2047,7 @@ impl Resolver {
     /// submodules.
     pub fn resolve_imports_for_module_subtree(&mut self,
                                               module_: @mut Module) {
-        debug!("(resolving imports for module subtree) resolving %s",
+        debug2!("(resolving imports for module subtree) resolving {}",
                self.module_to_str(module_));
         self.resolve_imports_for_module(module_);
 
@@ -2071,8 +2071,8 @@ impl Resolver {
     /// Attempts to resolve imports for the given module only.
     pub fn resolve_imports_for_module(&mut self, module: @mut Module) {
         if module.all_imports_resolved() {
-            debug!("(resolving imports for module) all imports resolved for \
-                   %s",
+            debug2!("(resolving imports for module) all imports resolved for \
+                   {}",
                    self.module_to_str(module));
             return;
         }
@@ -2085,7 +2085,7 @@ impl Resolver {
             match self.resolve_import_for_module(module, import_directive) {
                 Failed => {
                     // We presumably emitted an error. Continue.
-                    let msg = fmt!("failed to resolve import `%s`",
+                    let msg = format!("failed to resolve import `{}`",
                                    self.import_path_to_str(
                                        import_directive.module_path,
                                        *import_directive.subclass));
@@ -2142,7 +2142,7 @@ impl Resolver {
         if idents.is_empty() {
             self.import_directive_subclass_to_str(subclass)
         } else {
-            (fmt!("%s::%s",
+            (format!("{}::{}",
                   self.idents_to_str(idents),
                   self.import_directive_subclass_to_str(subclass))).to_managed()
         }
@@ -2160,8 +2160,8 @@ impl Resolver {
         let mut resolution_result = Failed;
         let module_path = &import_directive.module_path;
 
-        debug!("(resolving import for module) resolving import `%s::...` in \
-                `%s`",
+        debug2!("(resolving import for module) resolving import `{}::...` in \
+                `{}`",
                self.idents_to_str(*module_path),
                self.module_to_str(module_));
 
@@ -2263,8 +2263,8 @@ impl Resolver {
                                  source: Ident,
                                  directive: &ImportDirective)
                                  -> ResolveResult<()> {
-        debug!("(resolving single import) resolving `%s` = `%s::%s` from \
-                `%s`",
+        debug2!("(resolving single import) resolving `{}` = `{}::{}` from \
+                `{}`",
                self.session.str_of(target),
                self.module_to_str(containing_module),
                self.session.str_of(source),
@@ -2304,7 +2304,7 @@ impl Resolver {
                 // able to resolve this import.
 
                 if containing_module.glob_count > 0 {
-                    debug!("(resolving single import) unresolved glob; \
+                    debug2!("(resolving single import) unresolved glob; \
                             bailing out");
                     return Indeterminate;
                 }
@@ -2369,7 +2369,7 @@ impl Resolver {
                     }
                     Some(_) => {
                         // The import is unresolved. Bail out.
-                        debug!("(resolving single import) unresolved import; \
+                        debug2!("(resolving single import) unresolved import; \
                                 bailing out");
                         return Indeterminate;
                     }
@@ -2402,19 +2402,19 @@ impl Resolver {
 
         match value_result {
             BoundResult(target_module, name_bindings) => {
-                debug!("(resolving single import) found value target");
+                debug2!("(resolving single import) found value target");
                 import_resolution.value_target =
                     Some(Target::new(target_module, name_bindings));
                 import_resolution.value_id = directive.id;
             }
             UnboundResult => { /* Continue. */ }
             UnknownResult => {
-                fail!("value result should be known at this point");
+                fail2!("value result should be known at this point");
             }
         }
         match type_result {
             BoundResult(target_module, name_bindings) => {
-                debug!("(resolving single import) found type target: %?",
+                debug2!("(resolving single import) found type target: {:?}",
                         name_bindings.type_def.unwrap().type_def);
                 import_resolution.type_target =
                     Some(Target::new(target_module, name_bindings));
@@ -2422,7 +2422,7 @@ impl Resolver {
             }
             UnboundResult => { /* Continue. */ }
             UnknownResult => {
-                fail!("type result should be known at this point");
+                fail2!("type result should be known at this point");
             }
         }
 
@@ -2469,15 +2469,15 @@ impl Resolver {
 
         let span = directive.span;
         if resolve_fail {
-            let msg = fmt!("unresolved import: there is no `%s` in `%s`",
-                           self.session.str_of(source),
-                           self.module_to_str(containing_module));
+            let msg = format!("unresolved import: there is no `{}` in `{}`",
+                              self.session.str_of(source),
+                              self.module_to_str(containing_module));
             self.resolve_error(span, msg);
             return Failed;
         } else if priv_fail {
-            let msg = fmt!("unresolved import: found `%s` in `%s` but it is \
-                           private", self.session.str_of(source),
-                           self.module_to_str(containing_module));
+            let msg = format!("unresolved import: found `{}` in `{}` but it is \
+                              private", self.session.str_of(source),
+                              self.module_to_str(containing_module));
             self.resolve_error(span, msg);
             return Failed;
         }
@@ -2505,7 +2505,7 @@ impl Resolver {
             None => {}
         }
 
-        debug!("(resolving single import) successfully resolved import");
+        debug2!("(resolving single import) successfully resolved import");
         return Success(());
     }
 
@@ -2521,12 +2521,12 @@ impl Resolver {
         // This function works in a highly imperative manner; it eagerly adds
         // everything it can to the list of import resolutions of the module
         // node.
-        debug!("(resolving glob import) resolving %? glob import", privacy);
+        debug2!("(resolving glob import) resolving {:?} glob import", privacy);
 
         // We must bail out if the node has unresolved imports of any kind
         // (including globs).
         if !(*containing_module).all_imports_resolved() {
-            debug!("(resolving glob import) target module has unresolved \
+            debug2!("(resolving glob import) target module has unresolved \
                     imports; bailing out");
             return Indeterminate;
         }
@@ -2536,8 +2536,8 @@ impl Resolver {
         // Add all resolved imports from the containing module.
         for (ident, target_import_resolution) in containing_module.import_resolutions.iter() {
 
-            debug!("(resolving glob import) writing module resolution \
-                    %? into `%s`",
+            debug2!("(resolving glob import) writing module resolution \
+                    {:?} into `{}`",
                    target_import_resolution.type_target.is_none(),
                    self.module_to_str(module_));
 
@@ -2597,8 +2597,8 @@ impl Resolver {
                 }
             }
 
-            debug!("(resolving glob import) writing resolution `%s` in `%s` \
-                    to `%s`, privacy=%?",
+            debug2!("(resolving glob import) writing resolution `{}` in `{}` \
+                    to `{}`, privacy={:?}",
                    interner_get(name),
                    self.module_to_str(containing_module),
                    self.module_to_str(module_),
@@ -2606,13 +2606,13 @@ impl Resolver {
 
             // Merge the child item into the import resolution.
             if name_bindings.defined_in_public_namespace(ValueNS) {
-                debug!("(resolving glob import) ... for value target");
+                debug2!("(resolving glob import) ... for value target");
                 dest_import_resolution.value_target =
                     Some(Target::new(containing_module, name_bindings));
                 dest_import_resolution.value_id = id;
             }
             if name_bindings.defined_in_public_namespace(TypeNS) {
-                debug!("(resolving glob import) ... for type target");
+                debug2!("(resolving glob import) ... for type target");
                 dest_import_resolution.type_target =
                     Some(Target::new(containing_module, name_bindings));
                 dest_import_resolution.type_id = id;
@@ -2640,7 +2640,7 @@ impl Resolver {
             None => {}
         }
 
-        debug!("(resolving glob import) successfully resolved import");
+        debug2!("(resolving glob import) successfully resolved import");
         return Success(());
     }
 
@@ -2675,19 +2675,19 @@ impl Resolver {
                             expn_info: span.expn_info,
                         };
                         self.resolve_error(span,
-                                              fmt!("unresolved import. maybe \
+                                              format!("unresolved import. maybe \
                                                     a missing `extern mod \
-                                                    %s`?",
+                                                    {}`?",
                                                     segment_name));
                         return Failed;
                     }
-                    self.resolve_error(span, fmt!("unresolved import: could not find `%s` in \
-                                                     `%s`.", segment_name, module_name));
+                    self.resolve_error(span, format!("unresolved import: could not find `{}` in \
+                                                     `{}`.", segment_name, module_name));
                     return Failed;
                 }
                 Indeterminate => {
-                    debug!("(resolving module path for import) module \
-                            resolution is indeterminate: %s",
+                    debug2!("(resolving module path for import) module \
+                            resolution is indeterminate: {}",
                             self.session.str_of(name));
                     return Indeterminate;
                 }
@@ -2700,8 +2700,8 @@ impl Resolver {
                                 None => {
                                     // Not a module.
                                     self.resolve_error(span,
-                                                          fmt!("not a \
-                                                                module `%s`",
+                                                          format!("not a \
+                                                                module `{}`",
                                                                self.session.
                                                                    str_of(
                                                                     name)));
@@ -2729,7 +2729,7 @@ impl Resolver {
                         None => {
                             // There are no type bindings at all.
                             self.resolve_error(span,
-                                                  fmt!("not a module `%s`",
+                                                  format!("not a module `{}`",
                                                        self.session.str_of(
                                                             name)));
                             return Failed;
@@ -2764,8 +2764,8 @@ impl Resolver {
         let module_path_len = module_path.len();
         assert!(module_path_len > 0);
 
-        debug!("(resolving module path for import) processing `%s` rooted at \
-               `%s`",
+        debug2!("(resolving module path for import) processing `{}` rooted at \
+               `{}`",
                self.idents_to_str(module_path),
                self.module_to_str(module_));
 
@@ -2780,8 +2780,8 @@ impl Resolver {
                 let mpath = self.idents_to_str(module_path);
                 match mpath.rfind(':') {
                     Some(idx) => {
-                        self.resolve_error(span, fmt!("unresolved import: could not find `%s` \
-                                                         in `%s`",
+                        self.resolve_error(span, format!("unresolved import: could not find `{}` \
+                                                         in `{}`",
                                                          // idx +- 1 to account for the colons
                                                          // on either side
                                                          mpath.slice_from(idx + 1),
@@ -2792,7 +2792,7 @@ impl Resolver {
                 return Failed;
             }
             Indeterminate => {
-                debug!("(resolving module path for import) indeterminate; \
+                debug2!("(resolving module path for import) indeterminate; \
                         bailing");
                 return Indeterminate;
             }
@@ -2820,7 +2820,7 @@ impl Resolver {
                                 return Failed;
                             }
                             Indeterminate => {
-                                debug!("(resolving module path for import) \
+                                debug2!("(resolving module path for import) \
                                         indeterminate; bailing");
                                 return Indeterminate;
                             }
@@ -2854,8 +2854,8 @@ impl Resolver {
                                          search_through_modules:
                                          SearchThroughModulesFlag)
                                          -> ResolveResult<Target> {
-        debug!("(resolving item in lexical scope) resolving `%s` in \
-                namespace %? in `%s`",
+        debug2!("(resolving item in lexical scope) resolving `{}` in \
+                namespace {:?} in `{}`",
                self.session.str_of(name),
                namespace,
                self.module_to_str(module_));
@@ -2883,12 +2883,12 @@ impl Resolver {
                 match (*import_resolution).target_for_namespace(namespace) {
                     None => {
                         // Not found; continue.
-                        debug!("(resolving item in lexical scope) found \
-                                import resolution, but not in namespace %?",
+                        debug2!("(resolving item in lexical scope) found \
+                                import resolution, but not in namespace {:?}",
                                namespace);
                     }
                     Some(target) => {
-                        debug!("(resolving item in lexical scope) using \
+                        debug2!("(resolving item in lexical scope) using \
                                 import resolution");
                         self.used_imports.insert(import_resolution.id(namespace));
                         return Success(target);
@@ -2917,7 +2917,7 @@ impl Resolver {
             match search_module.parent_link {
                 NoParentLink => {
                     // No more parents. This module was unresolved.
-                    debug!("(resolving item in lexical scope) unresolved \
+                    debug2!("(resolving item in lexical scope) unresolved \
                             module");
                     return Failed;
                 }
@@ -2927,7 +2927,7 @@ impl Resolver {
                             match search_module.kind {
                                 NormalModuleKind => {
                                     // We stop the search here.
-                                    debug!("(resolving item in lexical \
+                                    debug2!("(resolving item in lexical \
                                             scope) unresolved module: not \
                                             searching through module \
                                             parents");
@@ -2963,7 +2963,7 @@ impl Resolver {
                     // We couldn't see through the higher scope because of an
                     // unresolved import higher up. Bail.
 
-                    debug!("(resolving item in lexical scope) indeterminate \
+                    debug2!("(resolving item in lexical scope) indeterminate \
                             higher scope; bailing");
                     return Indeterminate;
                 }
@@ -2991,7 +2991,7 @@ impl Resolver {
                     Some(ref type_def) => {
                         match (*type_def).module_def {
                             None => {
-                                error!("!!! (resolving module in lexical \
+                                error2!("!!! (resolving module in lexical \
                                         scope) module wasn't actually a \
                                         module!");
                                 return Failed;
@@ -3002,19 +3002,19 @@ impl Resolver {
                         }
                     }
                     None => {
-                        error!("!!! (resolving module in lexical scope) module
+                        error2!("!!! (resolving module in lexical scope) module
                                 wasn't actually a module!");
                         return Failed;
                     }
                 }
             }
             Indeterminate => {
-                debug!("(resolving module in lexical scope) indeterminate; \
+                debug2!("(resolving module in lexical scope) indeterminate; \
                         bailing");
                 return Indeterminate;
             }
             Failed => {
-                debug!("(resolving module in lexical scope) failed to \
+                debug2!("(resolving module in lexical scope) failed to \
                         resolve");
                 return Failed;
             }
@@ -3087,7 +3087,7 @@ impl Resolver {
         // Now loop through all the `super`s we find.
         while i < module_path.len() &&
                 "super" == token::ident_to_str(&module_path[i]) {
-            debug!("(resolving module prefix) resolving `super` at %s",
+            debug2!("(resolving module prefix) resolving `super` at {}",
                    self.module_to_str(containing_module));
             match self.get_nearest_normal_module_parent(containing_module) {
                 None => return Failed,
@@ -3098,7 +3098,7 @@ impl Resolver {
             }
         }
 
-        debug!("(resolving module prefix) finished resolving prefix at %s",
+        debug2!("(resolving module prefix) finished resolving prefix at {}",
                self.module_to_str(containing_module));
 
         return Success(PrefixFound(containing_module, i));
@@ -3113,7 +3113,7 @@ impl Resolver {
                                   namespace: Namespace,
                                   name_search_type: NameSearchType)
                                   -> ResolveResult<Target> {
-        debug!("(resolving name in module) resolving `%s` in `%s`",
+        debug2!("(resolving name in module) resolving `{}` in `{}`",
                self.session.str_of(name),
                self.module_to_str(module_));
 
@@ -3122,7 +3122,7 @@ impl Resolver {
         match module_.children.find(&name.name) {
             Some(name_bindings)
                     if name_bindings.defined_in_namespace(namespace) => {
-                debug!("(resolving name in module) found node as child");
+                debug2!("(resolving name in module) found node as child");
                 return Success(Target::new(module_, *name_bindings));
             }
             Some(_) | None => {
@@ -3144,28 +3144,28 @@ impl Resolver {
             Some(import_resolution) => {
                 if import_resolution.privacy == Public &&
                         import_resolution.outstanding_references != 0 {
-                    debug!("(resolving name in module) import \
+                    debug2!("(resolving name in module) import \
                             unresolved; bailing out");
                     return Indeterminate;
                 }
 
                 match import_resolution.target_for_namespace(namespace) {
                     None => {
-                        debug!("(resolving name in module) name found, \
-                                but not in namespace %?",
+                        debug2!("(resolving name in module) name found, \
+                                but not in namespace {:?}",
                                namespace);
                     }
                     Some(target)
                             if name_search_type ==
                                 PathPublicOrPrivateSearch ||
                             import_resolution.privacy == Public => {
-                        debug!("(resolving name in module) resolved to \
+                        debug2!("(resolving name in module) resolved to \
                                 import");
                         self.used_imports.insert(import_resolution.id(namespace));
                         return Success(target);
                     }
                     Some(_) => {
-                        debug!("(resolving name in module) name found, \
+                        debug2!("(resolving name in module) name found, \
                                 but not public");
                     }
                 }
@@ -3187,7 +3187,7 @@ impl Resolver {
         }
 
         // We're out of luck.
-        debug!("(resolving name in module) failed to resolve `%s`",
+        debug2!("(resolving name in module) failed to resolve `{}`",
                self.session.str_of(name));
         return Failed;
     }
@@ -3201,7 +3201,7 @@ impl Resolver {
             if sn.contains("::") {
                 self.resolve_error(imports[index].span, "unresolved import");
             } else {
-                let err = fmt!("unresolved import (maybe you meant `%s::*`?)",
+                let err = format!("unresolved import (maybe you meant `{}::*`?)",
                                sn.slice(0, sn.len()));
                 self.resolve_error(imports[index].span, err);
             }
@@ -3247,20 +3247,20 @@ impl Resolver {
         match module_.def_id {
             Some(def_id) if def_id.crate == LOCAL_CRATE => {
                 // OK. Continue.
-                debug!("(recording exports for module subtree) recording \
-                        exports for local module `%s`",
+                debug2!("(recording exports for module subtree) recording \
+                        exports for local module `{}`",
                        self.module_to_str(module_));
             }
             None => {
                 // Record exports for the root module.
-                debug!("(recording exports for module subtree) recording \
-                        exports for root module `%s`",
+                debug2!("(recording exports for module subtree) recording \
+                        exports for root module `{}`",
                        self.module_to_str(module_));
             }
             Some(_) => {
                 // Bail out.
-                debug!("(recording exports for module subtree) not recording \
-                        exports for `%s`",
+                debug2!("(recording exports for module subtree) not recording \
+                        exports for `{}`",
                        self.module_to_str(module_));
                 return;
             }
@@ -3292,7 +3292,7 @@ impl Resolver {
         match module_.def_id {
             Some(def_id) => {
                 self.export_map2.insert(def_id.node, exports2);
-                debug!("(computing exports) writing exports for %d (some)",
+                debug2!("(computing exports) writing exports for {} (some)",
                        def_id.node);
             }
             None => {}
@@ -3308,7 +3308,7 @@ impl Resolver {
         match (namebindings.def_for_namespace(ns),
                namebindings.privacy_for_namespace(ns)) {
             (Some(d), Some(Public)) => {
-                debug!("(computing exports) YES: %s '%s' => %?",
+                debug2!("(computing exports) YES: {} '{}' => {:?}",
                        if reexport { ~"reexport" } else { ~"export"},
                        interner_get(name),
                        def_id_of_def(d));
@@ -3319,10 +3319,10 @@ impl Resolver {
                 });
             }
             (Some(_), Some(privacy)) => {
-                debug!("(computing reexports) NO: privacy %?", privacy);
+                debug2!("(computing reexports) NO: privacy {:?}", privacy);
             }
             (d_opt, p_opt) => {
-                debug!("(computing reexports) NO: %?, %?", d_opt, p_opt);
+                debug2!("(computing reexports) NO: {:?}, {:?}", d_opt, p_opt);
             }
         }
     }
@@ -3332,7 +3332,7 @@ impl Resolver {
                                   module_: @mut Module) {
         for (name, importresolution) in module_.import_resolutions.iter() {
             if importresolution.privacy != Public {
-                debug!("(computing exports) not reexporting private `%s`",
+                debug2!("(computing exports) not reexporting private `{}`",
                        interner_get(*name));
                 loop;
             }
@@ -3340,7 +3340,7 @@ impl Resolver {
             for ns in xs.iter() {
                 match importresolution.target_for_namespace(*ns) {
                     Some(target) => {
-                        debug!("(computing exports) maybe reexport '%s'",
+                        debug2!("(computing exports) maybe reexport '{}'",
                                interner_get(*name));
                         self.add_exports_of_namebindings(&mut *exports2,
                                                          *name,
@@ -3384,15 +3384,15 @@ impl Resolver {
                 self.populate_module_if_necessary(orig_module);
                 match orig_module.children.find(&name.name) {
                     None => {
-                        debug!("!!! (with scope) didn't find `%s` in `%s`",
+                        debug2!("!!! (with scope) didn't find `{}` in `{}`",
                                self.session.str_of(name),
                                self.module_to_str(orig_module));
                     }
                     Some(name_bindings) => {
                         match (*name_bindings).get_module_if_available() {
                             None => {
-                                debug!("!!! (with scope) didn't find module \
-                                        for `%s` in `%s`",
+                                debug2!("!!! (with scope) didn't find module \
+                                        for `{}` in `{}`",
                                        self.session.str_of(name),
                                        self.module_to_str(orig_module));
                             }
@@ -3551,13 +3551,13 @@ impl Resolver {
     }
 
     pub fn resolve_crate(&mut self, crate: &ast::Crate) {
-        debug!("(resolving crate) starting");
+        debug2!("(resolving crate) starting");
 
         visit::walk_crate(self, crate, ());
     }
 
     pub fn resolve_item(&mut self, item: @item) {
-        debug!("(resolving item) resolving %s",
+        debug2!("(resolving item) resolving {}",
                self.session.str_of(item.ident));
 
         // Items with the !resolve_unexported attribute are X-ray contexts.
@@ -3727,7 +3727,7 @@ impl Resolver {
             }
 
           item_mac(*) => {
-            fail!("item macros unimplemented")
+            fail2!("item macros unimplemented")
           }
         }
 
@@ -3746,7 +3746,7 @@ impl Resolver {
 
                 for (index, type_parameter) in generics.ty_params.iter().enumerate() {
                     let ident = type_parameter.ident;
-                    debug!("with_type_parameter_rib: %d %d", node_id,
+                    debug2!("with_type_parameter_rib: {} {}", node_id,
                            type_parameter.id);
                     let def_like = DlDef(DefTyParam
                         (local_def(type_parameter.id),
@@ -3844,7 +3844,7 @@ impl Resolver {
 
                         this.resolve_type(&argument.ty);
 
-                        debug!("(resolving function) recorded argument");
+                        debug2!("(resolving function) recorded argument");
                     }
 
                     this.resolve_type(&declaration.output);
@@ -3854,7 +3854,7 @@ impl Resolver {
             // Resolve the function body.
             this.resolve_block(block);
 
-            debug!("(resolving function) leaving function");
+            debug2!("(resolving function) leaving function");
         }
 
         self.label_ribs.pop();
@@ -3894,11 +3894,11 @@ impl Resolver {
                     TraitDerivation            => "derive"
                 };
 
-                let msg = fmt!("attempt to %s a nonexistent trait `%s`", usage_str, path_str);
+                let msg = format!("attempt to {} a nonexistent trait `{}`", usage_str, path_str);
                 self.resolve_error(trait_reference.path.span, msg);
             }
             Some(def) => {
-                debug!("(resolving trait) found trait def: %?", def);
+                debug2!("(resolving trait) found trait def: {:?}", def);
                 self.record_def(trait_reference.ref_id, def);
             }
         }
@@ -3916,7 +3916,7 @@ impl Resolver {
                         Some(&prev_field) => {
                             let ident_str = self.session.str_of(ident);
                             self.resolve_error(field.span,
-                                fmt!("field `%s` is already declared", ident_str));
+                                format!("field `{}` is already declared", ident_str));
                             self.session.span_note(prev_field.span,
                                 "Previously declared here");
                         },
@@ -4049,7 +4049,7 @@ impl Resolver {
                           _name: Ident,
                           id: NodeId) {
         // Write the implementations in scope into the module metadata.
-        debug!("(resolving module) resolving module ID %d", id);
+        debug2!("(resolving module) resolving module ID {}", id);
         visit::walk_mod(self, module_, ());
     }
 
@@ -4101,16 +4101,16 @@ impl Resolver {
                   None => {
                     self.resolve_error(
                         p.span,
-                        fmt!("variable `%s` from pattern #1 is \
-                                  not bound in pattern #%u",
+                        format!("variable `{}` from pattern \\#1 is \
+                                  not bound in pattern \\#{}",
                              interner_get(key), i + 1));
                   }
                   Some(binding_i) => {
                     if binding_0.binding_mode != binding_i.binding_mode {
                         self.resolve_error(
                             binding_i.span,
-                            fmt!("variable `%s` is bound with different \
-                                      mode in pattern #%u than in pattern #1",
+                            format!("variable `{}` is bound with different \
+                                      mode in pattern \\#{} than in pattern \\#1",
                                  interner_get(key), i + 1));
                     }
                   }
@@ -4121,8 +4121,8 @@ impl Resolver {
                 if !map_0.contains_key(&key) {
                     self.resolve_error(
                         binding.span,
-                        fmt!("variable `%s` from pattern #%u is \
-                                  not bound in pattern #1",
+                        format!("variable `{}` from pattern \\#{} is \
+                                  not bound in pattern \\#1",
                              interner_get(key), i + 1));
                 }
             }
@@ -4149,7 +4149,7 @@ impl Resolver {
     }
 
     pub fn resolve_block(&mut self, block: &Block) {
-        debug!("(resolving block) entering block");
+        debug2!("(resolving block) entering block");
         self.value_ribs.push(@Rib::new(NormalRibKind));
 
         // Move down in the graph, if there's an anonymous module rooted here.
@@ -4157,7 +4157,7 @@ impl Resolver {
         match self.current_module.anonymous_children.find(&block.id) {
             None => { /* Nothing to do. */ }
             Some(&anonymous_module) => {
-                debug!("(resolving block) found anonymous module, moving \
+                debug2!("(resolving block) found anonymous module, moving \
                         down");
                 self.current_module = anonymous_module;
             }
@@ -4170,7 +4170,7 @@ impl Resolver {
         self.current_module = orig_module;
 
         self.value_ribs.pop();
-        debug!("(resolving block) leaving block");
+        debug2!("(resolving block) leaving block");
     }
 
     pub fn resolve_type(&mut self, ty: &Ty) {
@@ -4224,8 +4224,8 @@ impl Resolver {
                                                 TypeNS,
                                                 true) {
                             Some(def) => {
-                                debug!("(resolving type) resolved `%s` to \
-                                        type %?",
+                                debug2!("(resolving type) resolved `{}` to \
+                                        type {:?}",
                                        self.session.str_of(path.segments
                                                                .last()
                                                                .identifier),
@@ -4243,15 +4243,15 @@ impl Resolver {
                 match result_def {
                     Some(def) => {
                         // Write the result into the def map.
-                        debug!("(resolving type) writing resolution for `%s` \
-                                (id %d)",
+                        debug2!("(resolving type) writing resolution for `{}` \
+                                (id {})",
                                self.path_idents_to_str(path),
                                path_id);
                         self.record_def(path_id, def);
                     }
                     None => {
-                        let msg = fmt!("use of undeclared type name `%s`",
-                                       self.path_idents_to_str(path));
+                        let msg = format!("use of undeclared type name `{}`",
+                                          self.path_idents_to_str(path));
                         self.resolve_error(ty.span, msg);
                     }
                 }
@@ -4307,7 +4307,7 @@ impl Resolver {
                     match self.resolve_bare_identifier_pattern(ident) {
                         FoundStructOrEnumVariant(def)
                                 if mode == RefutableMode => {
-                            debug!("(resolving pattern) resolving `%s` to \
+                            debug2!("(resolving pattern) resolving `{}` to \
                                     struct or enum variant",
                                    interner_get(renamed));
 
@@ -4319,14 +4319,14 @@ impl Resolver {
                         }
                         FoundStructOrEnumVariant(_) => {
                             self.resolve_error(pattern.span,
-                                                  fmt!("declaration of `%s` \
+                                                  format!("declaration of `{}` \
                                                         shadows an enum \
                                                         variant or unit-like \
                                                         struct in scope",
                                                        interner_get(renamed)));
                         }
                         FoundConst(def) if mode == RefutableMode => {
-                            debug!("(resolving pattern) resolving `%s` to \
+                            debug2!("(resolving pattern) resolving `{}` to \
                                     constant",
                                    interner_get(renamed));
 
@@ -4342,7 +4342,7 @@ impl Resolver {
                                                    allowed here");
                         }
                         BareIdentifierPatternUnresolved => {
-                            debug!("(resolving pattern) binding `%s`",
+                            debug2!("(resolving pattern) binding `{}`",
                                    interner_get(renamed));
 
                             let is_mutable = mutability == Mutable;
@@ -4392,7 +4392,7 @@ impl Resolver {
                                       // in the same disjunct, which is an
                                       // error
                                      self.resolve_error(pattern.span,
-                                       fmt!("Identifier `%s` is bound more \
+                                       format!("Identifier `{}` is bound more \
                                              than once in the same pattern",
                                             path_to_str(path, self.session
                                                         .intr())));
@@ -4435,7 +4435,7 @@ impl Resolver {
                         Some(_) => {
                             self.resolve_error(
                                 path.span,
-                                fmt!("`%s` is not an enum variant or constant",
+                                format!("`{}` is not an enum variant or constant",
                                      self.session.str_of(
                                          path.segments.last().identifier)))
                         }
@@ -4465,7 +4465,7 @@ impl Resolver {
                         Some(_) => {
                             self.resolve_error(
                                 path.span,
-                                fmt!("`%s` is not an enum variant, struct or const",
+                                format!("`{}` is not an enum variant, struct or const",
                                      self.session
                                          .str_of(path.segments
                                                      .last()
@@ -4473,8 +4473,8 @@ impl Resolver {
                         }
                         None => {
                             self.resolve_error(path.span,
-                                               fmt!("unresolved enum variant, \
-                                                    struct or const `%s`",
+                                               format!("unresolved enum variant, \
+                                                    struct or const `{}`",
                                                     self.session
                                                         .str_of(path.segments
                                                                     .last()
@@ -4515,10 +4515,10 @@ impl Resolver {
                             self.record_def(pattern.id, definition);
                         }
                         result => {
-                            debug!("(resolving pattern) didn't find struct \
-                                    def: %?", result);
-                            let msg = fmt!("`%s` does not name a structure",
-                                           self.path_idents_to_str(path));
+                            debug2!("(resolving pattern) didn't find struct \
+                                    def: {:?}", result);
+                            let msg = format!("`{}` does not name a structure",
+                                              self.path_idents_to_str(path));
                             self.resolve_error(path.span, msg);
                         }
                     }
@@ -4542,7 +4542,7 @@ impl Resolver {
             Success(target) => {
                 match target.bindings.value_def {
                     None => {
-                        fail!("resolved name in the value namespace to a \
+                        fail2!("resolved name in the value namespace to a \
                               set of name bindings with no def?!");
                     }
                     Some(def) => {
@@ -4562,7 +4562,7 @@ impl Resolver {
             }
 
             Indeterminate => {
-                fail!("unexpected indeterminate result");
+                fail2!("unexpected indeterminate result");
             }
 
             Failed => {
@@ -4732,14 +4732,14 @@ impl Resolver {
                                        path.span,
                                        PathPublicOnlySearch) {
             Failed => {
-                let msg = fmt!("use of undeclared module `%s`",
-                               self.idents_to_str(module_path_idents));
+                let msg = format!("use of undeclared module `{}`",
+                                  self.idents_to_str(module_path_idents));
                 self.resolve_error(path.span, msg);
                 return None;
             }
 
             Indeterminate => {
-                fail!("indeterminate unexpected");
+                fail2!("indeterminate unexpected");
             }
 
             Success(resulting_module) => {
@@ -4766,7 +4766,7 @@ impl Resolver {
                     Some(s) => {
                         match containing_module.def_id {
                             Some(def_id) if s.contains(&def_id) => {
-                                debug!("containing module was a trait or impl \
+                                debug2!("containing module was a trait or impl \
                                         and name was a method -> not resolved");
                                 return None;
                             },
@@ -4799,14 +4799,14 @@ impl Resolver {
                                                  path.span,
                                                  PathPublicOrPrivateSearch) {
             Failed => {
-                let msg = fmt!("use of undeclared module `::%s`",
-                               self.idents_to_str(module_path_idents));
+                let msg = format!("use of undeclared module `::{}`",
+                                  self.idents_to_str(module_path_idents));
                 self.resolve_error(path.span, msg);
                 return None;
             }
 
             Indeterminate => {
-                fail!("indeterminate unexpected");
+                fail2!("indeterminate unexpected");
             }
 
             Success(resulting_module) => {
@@ -4852,8 +4852,8 @@ impl Resolver {
 
         match search_result {
             Some(DlDef(def)) => {
-                debug!("(resolving path in local ribs) resolved `%s` to \
-                        local: %?",
+                debug2!("(resolving path in local ribs) resolved `{}` to \
+                        local: {:?}",
                        self.session.str_of(ident),
                        def);
                 return Some(def);
@@ -4913,15 +4913,15 @@ impl Resolver {
                         return None;
                     }
                     Some(def) => {
-                        debug!("(resolving item path in lexical scope) \
-                                resolved `%s` to item",
+                        debug2!("(resolving item path in lexical scope) \
+                                resolved `{}` to item",
                                self.session.str_of(ident));
                         return Some(def);
                     }
                 }
             }
             Indeterminate => {
-                fail!("unexpected indeterminate result");
+                fail2!("unexpected indeterminate result");
             }
             Failed => {
                 return None;
@@ -5000,7 +5000,7 @@ impl Resolver {
                 match self.resolve_path(expr.id, path, ValueNS, true) {
                     Some(def) => {
                         // Write the result into the def map.
-                        debug!("(resolving expr) resolved `%s`",
+                        debug2!("(resolving expr) resolved `{}`",
                                self.path_idents_to_str(path));
 
                         // First-class methods are not supported yet; error
@@ -5031,11 +5031,15 @@ impl Resolver {
                             Some(DefTy(struct_id))
                               if self.structs.contains(&struct_id) => {
                                 self.resolve_error(expr.span,
-                                        fmt!("`%s` is a structure name, but this expression \
-                                            uses it like a function name", wrong_name));
+                                        format!("`{}` is a structure name, but \
+                                                 this expression \
+                                                 uses it like a function name",
+                                                wrong_name));
 
-                                self.session.span_note(expr.span, fmt!("Did you mean to write: \
-                                            `%s { /* fields */ }`?", wrong_name));
+                                self.session.span_note(expr.span,
+                                    format!("Did you mean to write: \
+                                            `{} \\{ /* fields */ \\}`?",
+                                            wrong_name));
 
                             }
                             _ =>
@@ -5044,14 +5048,14 @@ impl Resolver {
                                match self.find_best_match_for_name(wrong_name, 5) {
                                    Some(m) => {
                                        self.resolve_error(expr.span,
-                                           fmt!("unresolved name `%s`. \
-                                               Did you mean `%s`?",
-                                               wrong_name, m));
+                                           format!("unresolved name `{}`. \
+                                                    Did you mean `{}`?",
+                                                    wrong_name, m));
                                    }
                                    None => {
                                        self.resolve_error(expr.span,
-                                            fmt!("unresolved name `%s`.",
-                                                wrong_name));
+                                            format!("unresolved name `{}`.",
+                                                    wrong_name));
                                    }
                                }
                         }
@@ -5082,10 +5086,10 @@ impl Resolver {
                         self.record_def(expr.id, definition);
                     }
                     result => {
-                        debug!("(resolving expression) didn't find struct \
-                                def: %?", result);
-                        let msg = fmt!("`%s` does not name a structure",
-                                       self.path_idents_to_str(path));
+                        debug2!("(resolving expression) didn't find struct \
+                                def: {:?}", result);
+                        let msg = format!("`{}` does not name a structure",
+                                          self.path_idents_to_str(path));
                         self.resolve_error(path.span, msg);
                     }
                 }
@@ -5104,15 +5108,15 @@ impl Resolver {
                 }
             }
 
-            ExprForLoop(*) => fail!("non-desugared expr_for_loop"),
+            ExprForLoop(*) => fail2!("non-desugared expr_for_loop"),
 
             ExprBreak(Some(label)) | ExprAgain(Some(label)) => {
                 match self.search_ribs(self.label_ribs, label, expr.span,
                                        DontAllowCapturingSelf) {
                     None =>
                         self.resolve_error(expr.span,
-                                              fmt!("use of undeclared label \
-                                                   `%s`",
+                                              format!("use of undeclared label \
+                                                   `{}`",
                                                    interner_get(label))),
                     Some(DlDef(def @ DefLabel(_))) => {
                         self.record_def(expr.id, def)
@@ -5154,8 +5158,8 @@ impl Resolver {
                 self.trait_map.insert(expr.id, @mut traits);
             }
             ExprMethodCall(_, _, ident, _, _, _) => {
-                debug!("(recording candidate traits for expr) recording \
-                        traits for %d",
+                debug2!("(recording candidate traits for expr) recording \
+                        traits for {}",
                        expr.id);
                 let traits = self.search_for_traits_containing_method(ident);
                 self.trait_map.insert(expr.id, @mut traits);
@@ -5229,7 +5233,7 @@ impl Resolver {
 
     pub fn search_for_traits_containing_method(&mut self, name: Ident)
                                                -> ~[DefId] {
-        debug!("(searching for traits containing method) looking for '%s'",
+        debug2!("(searching for traits containing method) looking for '{}'",
                self.session.str_of(name));
 
         let mut found_traits = ~[];
@@ -5331,7 +5335,7 @@ impl Resolver {
                           found_traits: &mut ~[DefId],
                           trait_def_id: DefId,
                           name: Ident) {
-        debug!("(adding trait info) found trait %d:%d for method '%s'",
+        debug2!("(adding trait info) found trait {}:{} for method '{}'",
                trait_def_id.crate,
                trait_def_id.node,
                self.session.str_of(name));
@@ -5350,14 +5354,14 @@ impl Resolver {
     }
 
     pub fn record_def(&mut self, node_id: NodeId, def: Def) {
-        debug!("(recording def) recording %? for %?", def, node_id);
+        debug2!("(recording def) recording {:?} for {:?}", def, node_id);
         do self.def_map.insert_or_update_with(node_id, def) |_, old_value| {
             // Resolve appears to "resolve" the same ID multiple
             // times, so here is a sanity check it at least comes to
             // the same conclusion! - nmatsakis
             if def != *old_value {
-                self.session.bug(fmt!("node_id %? resolved first to %? \
-                                      and then %?", node_id, *old_value, def));
+                self.session.bug(format!("node_id {:?} resolved first to {:?} \
+                                      and then {:?}", node_id, *old_value, def));
             }
         };
     }
@@ -5371,7 +5375,7 @@ impl Resolver {
             BindByRef(*) => {
                 self.resolve_error(
                     pat.span,
-                    fmt!("cannot use `ref` binding mode with %s",
+                    format!("cannot use `ref` binding mode with {}",
                          descr));
             }
         }
@@ -5459,15 +5463,15 @@ impl Resolver {
     }
 
     pub fn dump_module(&mut self, module_: @mut Module) {
-        debug!("Dump of module `%s`:", self.module_to_str(module_));
+        debug2!("Dump of module `{}`:", self.module_to_str(module_));
 
-        debug!("Children:");
+        debug2!("Children:");
         self.populate_module_if_necessary(module_);
         for (&name, _) in module_.children.iter() {
-            debug!("* %s", interner_get(name));
+            debug2!("* {}", interner_get(name));
         }
 
-        debug!("Import resolutions:");
+        debug2!("Import resolutions:");
         for (name, import_resolution) in module_.import_resolutions.iter() {
             let value_repr;
             match import_resolution.target_for_namespace(ValueNS) {
@@ -5487,7 +5491,7 @@ impl Resolver {
                 }
             }
 
-            debug!("* %s:%s%s", interner_get(*name),
+            debug2!("* {}:{}{}", interner_get(*name),
                    value_repr, type_repr);
         }
     }
diff --git a/src/librustc/middle/stack_check.rs b/src/librustc/middle/stack_check.rs
index 44de6fde050..1c572b2cbad 100644
--- a/src/librustc/middle/stack_check.rs
+++ b/src/librustc/middle/stack_check.rs
@@ -123,20 +123,20 @@ fn stack_check_fn<'a>(v: &mut StackCheckVisitor,
         }
     };
     let new_cx = Context {safe_stack: safe_stack};
-    debug!("stack_check_fn(safe_stack=%b, id=%?)", safe_stack, id);
+    debug2!("stack_check_fn(safe_stack={}, id={:?})", safe_stack, id);
     visit::walk_fn(v, fk, decl, body, sp, id, new_cx);
 }
 
 fn stack_check_expr<'a>(v: &mut StackCheckVisitor,
                         expr: @ast::Expr,
                         cx: Context) {
-    debug!("stack_check_expr(safe_stack=%b, expr=%s)",
+    debug2!("stack_check_expr(safe_stack={}, expr={})",
            cx.safe_stack, expr.repr(v.tcx));
     if !cx.safe_stack {
         match expr.node {
             ast::ExprCall(callee, _, _) => {
                 let callee_ty = ty::expr_ty(v.tcx, callee);
-                debug!("callee_ty=%s", callee_ty.repr(v.tcx));
+                debug2!("callee_ty={}", callee_ty.repr(v.tcx));
                 match ty::get(callee_ty).sty {
                     ty::ty_bare_fn(ref fty) => {
                         if !fty.abis.is_rust() && !fty.abis.is_intrinsic() {
@@ -177,6 +177,6 @@ fn call_to_extern_fn(v: &mut StackCheckVisitor, callee: @ast::Expr) {
     v.tcx.sess.add_lint(lint::cstack,
                          callee.id,
                          callee.span,
-                         fmt!("invoking non-Rust fn in fn without \
-                              #[fixed_stack_segment]"));
+                         format!("invoking non-Rust fn in fn without \
+                              \\#[fixed_stack_segment]"));
 }
diff --git a/src/librustc/middle/subst.rs b/src/librustc/middle/subst.rs
index 7b2b130bc68..40cd693b5c1 100644
--- a/src/librustc/middle/subst.rs
+++ b/src/librustc/middle/subst.rs
@@ -183,9 +183,9 @@ impl Subst for ty::Region {
                     ty::NonerasedRegions(ref regions) => {
                         if regions.len() != 1 {
                             tcx.sess.bug(
-                                fmt!("ty::Region#subst(): \
+                                format!("ty::Region\\#subst(): \
                                       Reference to self region when \
-                                      given substs with no self region: %s",
+                                      given substs with no self region: {}",
                                      substs.repr(tcx)));
                         }
                         *regions.get(0)
diff --git a/src/librustc/middle/trans/_match.rs b/src/librustc/middle/trans/_match.rs
index c2dbcfa3b57..a159512aee5 100644
--- a/src/librustc/middle/trans/_match.rs
+++ b/src/librustc/middle/trans/_match.rs
@@ -264,7 +264,7 @@ fn opt_eq(tcx: ty::ctxt, a: &Opt, b: &Opt) -> bool {
                                 a_expr = e.unwrap();
                             }
                         UnitLikeStructLit(_) => {
-                            fail!("UnitLikeStructLit should have been handled \
+                            fail2!("UnitLikeStructLit should have been handled \
                                     above")
                         }
                     }
@@ -277,14 +277,14 @@ fn opt_eq(tcx: ty::ctxt, a: &Opt, b: &Opt) -> bool {
                                 b_expr = e.unwrap();
                             }
                         UnitLikeStructLit(_) => {
-                            fail!("UnitLikeStructLit should have been handled \
+                            fail2!("UnitLikeStructLit should have been handled \
                                     above")
                         }
                     }
 
                     match const_eval::compare_lit_exprs(tcx, a_expr, b_expr) {
                         Some(val1) => val1 == 0,
-                        None => fail!("compare_list_exprs: type mismatch"),
+                        None => fail2!("compare_list_exprs: type mismatch"),
                     }
                 }
             }
@@ -294,7 +294,7 @@ fn opt_eq(tcx: ty::ctxt, a: &Opt, b: &Opt) -> bool {
             let m2 = const_eval::compare_lit_exprs(tcx, a2, b2);
             match (m1, m2) {
                 (Some(val1), Some(val2)) => (val1 == 0 && val2 == 0),
-                _ => fail!("compare_list_exprs: type mismatch"),
+                _ => fail2!("compare_list_exprs: type mismatch"),
             }
         }
         (&var(a, _), &var(b, _)) => a == b,
@@ -419,7 +419,7 @@ impl<'self> Repr for Match<'self> {
             // for many programs, this just take too long to serialize
             self.pats.repr(tcx)
         } else {
-            fmt!("%u pats", self.pats.len())
+            format!("{} pats", self.pats.len())
         }
     }
 }
@@ -439,7 +439,7 @@ fn expand_nested_bindings<'r>(bcx: @mut Block,
                                   col: uint,
                                   val: ValueRef)
                               -> ~[Match<'r>] {
-    debug!("expand_nested_bindings(bcx=%s, m=%s, col=%u, val=%s)",
+    debug2!("expand_nested_bindings(bcx={}, m={}, col={}, val={})",
            bcx.to_str(),
            m.repr(bcx.tcx()),
            col,
@@ -472,7 +472,7 @@ fn assert_is_binding_or_wild(bcx: @mut Block, p: @ast::Pat) {
     if !pat_is_binding_or_wild(bcx.tcx().def_map, p) {
         bcx.sess().span_bug(
             p.span,
-            fmt!("Expected an identifier pattern but found p: %s",
+            format!("Expected an identifier pattern but found p: {}",
                  p.repr(bcx.tcx())));
     }
 }
@@ -486,7 +486,7 @@ fn enter_match<'r>(bcx: @mut Block,
                        val: ValueRef,
                        e: enter_pat)
                     -> ~[Match<'r>] {
-    debug!("enter_match(bcx=%s, m=%s, col=%u, val=%s)",
+    debug2!("enter_match(bcx={}, m={}, col={}, val={})",
            bcx.to_str(),
            m.repr(bcx.tcx()),
            col,
@@ -523,7 +523,7 @@ fn enter_match<'r>(bcx: @mut Block,
         }
     }
 
-    debug!("result=%s", result.repr(bcx.tcx()));
+    debug2!("result={}", result.repr(bcx.tcx()));
 
     return result;
 }
@@ -535,7 +535,7 @@ fn enter_default<'r>(bcx: @mut Block,
                      val: ValueRef,
                      chk: FailureHandler)
                       -> ~[Match<'r>] {
-    debug!("enter_default(bcx=%s, m=%s, col=%u, val=%s)",
+    debug2!("enter_default(bcx={}, m={}, col={}, val={})",
            bcx.to_str(),
            m.repr(bcx.tcx()),
            col,
@@ -605,7 +605,7 @@ fn enter_opt<'r>(bcx: @mut Block,
                      variant_size: uint,
                      val: ValueRef)
                   -> ~[Match<'r>] {
-    debug!("enter_opt(bcx=%s, m=%s, opt=%?, col=%u, val=%s)",
+    debug2!("enter_opt(bcx={}, m={}, opt={:?}, col={}, val={})",
            bcx.to_str(),
            m.repr(bcx.tcx()),
            *opt,
@@ -741,7 +741,7 @@ fn enter_rec_or_struct<'r>(bcx: @mut Block,
                                fields: &[ast::Ident],
                                val: ValueRef)
                             -> ~[Match<'r>] {
-    debug!("enter_rec_or_struct(bcx=%s, m=%s, col=%u, val=%s)",
+    debug2!("enter_rec_or_struct(bcx={}, m={}, col={}, val={})",
            bcx.to_str(),
            m.repr(bcx.tcx()),
            col,
@@ -776,7 +776,7 @@ fn enter_tup<'r>(bcx: @mut Block,
                      val: ValueRef,
                      n_elts: uint)
                   -> ~[Match<'r>] {
-    debug!("enter_tup(bcx=%s, m=%s, col=%u, val=%s)",
+    debug2!("enter_tup(bcx={}, m={}, col={}, val={})",
            bcx.to_str(),
            m.repr(bcx.tcx()),
            col,
@@ -802,7 +802,7 @@ fn enter_tuple_struct<'r>(bcx: @mut Block,
                               val: ValueRef,
                               n_elts: uint)
                           -> ~[Match<'r>] {
-    debug!("enter_tuple_struct(bcx=%s, m=%s, col=%u, val=%s)",
+    debug2!("enter_tuple_struct(bcx={}, m={}, col={}, val={})",
            bcx.to_str(),
            m.repr(bcx.tcx()),
            col,
@@ -827,7 +827,7 @@ fn enter_box<'r>(bcx: @mut Block,
                      col: uint,
                      val: ValueRef)
                  -> ~[Match<'r>] {
-    debug!("enter_box(bcx=%s, m=%s, col=%u, val=%s)",
+    debug2!("enter_box(bcx={}, m={}, col={}, val={})",
            bcx.to_str(),
            m.repr(bcx.tcx()),
            col,
@@ -854,7 +854,7 @@ fn enter_uniq<'r>(bcx: @mut Block,
                       col: uint,
                       val: ValueRef)
                   -> ~[Match<'r>] {
-    debug!("enter_uniq(bcx=%s, m=%s, col=%u, val=%s)",
+    debug2!("enter_uniq(bcx={}, m={}, col={}, val={})",
            bcx.to_str(),
            m.repr(bcx.tcx()),
            col,
@@ -881,7 +881,7 @@ fn enter_region<'r>(bcx: @mut Block,
                         col: uint,
                         val: ValueRef)
                     -> ~[Match<'r>] {
-    debug!("enter_region(bcx=%s, m=%s, col=%u, val=%s)",
+    debug2!("enter_region(bcx={}, m={}, col={}, val={})",
            bcx.to_str(),
            m.repr(bcx.tcx()),
            col,
@@ -1232,7 +1232,7 @@ impl FailureHandler {
     fn handle_fail(&self) -> BasicBlockRef {
         match *self {
             Infallible => {
-                fail!("attempted to fail in infallible failure handler!")
+                fail2!("attempted to fail in infallible failure handler!")
             }
             JumpToBasicBlock(basic_block) => basic_block,
             CustomFailureHandlerClass(custom_failure_handler) => {
@@ -1295,7 +1295,7 @@ fn compare_values(cx: @mut Block,
             let scratch_rhs = alloca(cx, val_ty(rhs), "__rhs");
             Store(cx, rhs, scratch_rhs);
             let did = langcall(cx, None,
-                               fmt!("comparison of `%s`", cx.ty_to_str(rhs_t)),
+                               format!("comparison of `{}`", cx.ty_to_str(rhs_t)),
                                UniqStrEqFnLangItem);
             let result = callee::trans_lang_call(cx, did, [scratch_lhs, scratch_rhs], None);
             Result {
@@ -1305,7 +1305,7 @@ fn compare_values(cx: @mut Block,
         }
         ty::ty_estr(_) => {
             let did = langcall(cx, None,
-                               fmt!("comparison of `%s`", cx.ty_to_str(rhs_t)),
+                               format!("comparison of `{}`", cx.ty_to_str(rhs_t)),
                                StrEqFnLangItem);
             let result = callee::trans_lang_call(cx, did, [lhs, rhs], None);
             Result {
@@ -1383,7 +1383,7 @@ fn insert_lllocals(bcx: @mut Block,
             }
         };
 
-        debug!("binding %? to %s", binding_info.id, bcx.val_to_str(llval));
+        debug2!("binding {:?} to {}", binding_info.id, bcx.val_to_str(llval));
         llmap.insert(binding_info.id, llval);
 
         if bcx.sess().opts.extra_debuginfo {
@@ -1404,7 +1404,7 @@ fn compile_guard(bcx: @mut Block,
                      vals: &[ValueRef],
                      chk: FailureHandler)
                   -> @mut Block {
-    debug!("compile_guard(bcx=%s, guard_expr=%s, m=%s, vals=%s)",
+    debug2!("compile_guard(bcx={}, guard_expr={}, m={}, vals={})",
            bcx.to_str(),
            bcx.expr_to_str(guard_expr),
            m.repr(bcx.tcx()),
@@ -1458,7 +1458,7 @@ fn compile_submatch(bcx: @mut Block,
                     m: &[Match],
                     vals: &[ValueRef],
                     chk: FailureHandler) {
-    debug!("compile_submatch(bcx=%s, m=%s, vals=%s)",
+    debug2!("compile_submatch(bcx={}, m={}, vals={})",
            bcx.to_str(),
            m.repr(bcx.tcx()),
            vec_map_to_str(vals, |v| bcx.val_to_str(*v)));
@@ -1624,7 +1624,7 @@ fn compile_submatch_continue(mut bcx: @mut Block,
 
     // Decide what kind of branch we need
     let opts = get_options(bcx, m, col);
-    debug!("options=%?", opts);
+    debug2!("options={:?}", opts);
     let mut kind = no_branch;
     let mut test_val = val;
     if opts.len() > 0u {
@@ -2113,13 +2113,13 @@ fn bind_irrefutable_pat(bcx: @mut Block,
      * - binding_mode: is this for an argument or a local variable?
      */
 
-    debug!("bind_irrefutable_pat(bcx=%s, pat=%s, binding_mode=%?)",
+    debug2!("bind_irrefutable_pat(bcx={}, pat={}, binding_mode={:?})",
            bcx.to_str(),
            pat.repr(bcx.tcx()),
            binding_mode);
 
     if bcx.sess().asm_comments() {
-        add_comment(bcx, fmt!("bind_irrefutable_pat(pat=%s)",
+        add_comment(bcx, format!("bind_irrefutable_pat(pat={})",
                               pat.repr(bcx.tcx())));
     }
 
@@ -2241,7 +2241,7 @@ fn bind_irrefutable_pat(bcx: @mut Block,
         ast::PatVec(*) => {
             bcx.tcx().sess.span_bug(
                 pat.span,
-                fmt!("vector patterns are never irrefutable!"));
+                format!("vector patterns are never irrefutable!"));
         }
         ast::PatWild | ast::PatLit(_) | ast::PatRange(_, _) => ()
     }
diff --git a/src/librustc/middle/trans/adt.rs b/src/librustc/middle/trans/adt.rs
index 5c255ad0818..0fdbc04a6c1 100644
--- a/src/librustc/middle/trans/adt.rs
+++ b/src/librustc/middle/trans/adt.rs
@@ -113,13 +113,13 @@ pub fn represent_node(bcx: @mut Block, node: ast::NodeId) -> @Repr {
 
 /// Decides how to represent a given type.
 pub fn represent_type(cx: &mut CrateContext, t: ty::t) -> @Repr {
-    debug!("Representing: %s", ty_to_str(cx.tcx, t));
+    debug2!("Representing: {}", ty_to_str(cx.tcx, t));
     match cx.adt_reprs.find(&t) {
         Some(repr) => return *repr,
         None => { }
     }
     let repr = @represent_type_uncached(cx, t);
-    debug!("Represented as: %?", repr)
+    debug2!("Represented as: {:?}", repr)
     cx.adt_reprs.insert(t, repr);
     return repr;
 }
@@ -179,7 +179,7 @@ fn represent_type_uncached(cx: &mut CrateContext, t: ty::t) -> Repr {
             // non-empty body, explicit discriminants should have
             // been rejected by a checker before this point.
             if !cases.iter().enumerate().all(|(i,c)| c.discr == (i as Disr)) {
-                cx.sess.bug(fmt!("non-C-like enum %s with specified \
+                cx.sess.bug(format!("non-C-like enum {} with specified \
                                   discriminants",
                                  ty::item_path_str(cx.tcx, def_id)))
             }
diff --git a/src/librustc/middle/trans/asm.rs b/src/librustc/middle/trans/asm.rs
index de4ea331041..4a960b1721d 100644
--- a/src/librustc/middle/trans/asm.rs
+++ b/src/librustc/middle/trans/asm.rs
@@ -47,7 +47,7 @@ pub fn trans_inline_asm(bcx: @mut Block, ia: &ast::inline_asm) -> @mut Block {
 
         let e = match out.node {
             ast::ExprAddrOf(_, e) => e,
-            _ => fail!("Expression must be addr of")
+            _ => fail2!("Expression must be addr of")
         };
 
         unpack_result!(bcx, {
@@ -89,7 +89,7 @@ pub fn trans_inline_asm(bcx: @mut Block, ia: &ast::inline_asm) -> @mut Block {
 
     let mut clobbers = getClobbers();
     if !ia.clobbers.is_empty() && !clobbers.is_empty() {
-        clobbers = fmt!("%s,%s", ia.clobbers, clobbers);
+        clobbers = format!("{},{}", ia.clobbers, clobbers);
     } else {
         clobbers.push_str(ia.clobbers);
     };
@@ -102,7 +102,7 @@ pub fn trans_inline_asm(bcx: @mut Block, ia: &ast::inline_asm) -> @mut Block {
         constraints.push_str(clobbers);
     }
 
-    debug!("Asm Constraints: %?", constraints);
+    debug2!("Asm Constraints: {:?}", constraints);
 
     let numOutputs = outputs.len();
 
diff --git a/src/librustc/middle/trans/base.rs b/src/librustc/middle/trans/base.rs
index 264ad3c7c57..3a35f144ab5 100644
--- a/src/librustc/middle/trans/base.rs
+++ b/src/librustc/middle/trans/base.rs
@@ -351,7 +351,7 @@ pub fn malloc_raw_dyn(bcx: @mut Block,
         match li.require(it) {
             Ok(id) => id,
             Err(s) => {
-                bcx.tcx().sess.fatal(fmt!("allocation of `%s` %s",
+                bcx.tcx().sess.fatal(format!("allocation of `{}` {}",
                                           bcx.ty_to_str(t), s));
             }
         }
@@ -379,7 +379,7 @@ pub fn malloc_raw_dyn(bcx: @mut Block,
                 (ty::mk_imm_box,
                  require_alloc_fn(bcx, t, ClosureExchangeMallocFnLangItem))
             }
-            _ => fail!("heap_exchange already handled")
+            _ => fail2!("heap_exchange already handled")
         };
 
         // Grab the TypeRef type of box_ptr_ty.
@@ -911,20 +911,18 @@ pub fn invoke(bcx: @mut Block, llfn: ValueRef, llargs: ~[ValueRef],
     }
 
     match bcx.node_info {
-        None => debug!("invoke at ???"),
+        None => debug2!("invoke at ???"),
         Some(node_info) => {
-            debug!("invoke at %s",
+            debug2!("invoke at {}",
                    bcx.sess().codemap.span_to_str(node_info.span));
         }
     }
 
     if need_invoke(bcx) {
         unsafe {
-            debug!("invoking %x at %x",
-                   ::std::cast::transmute(llfn),
-                   ::std::cast::transmute(bcx.llbb));
+            debug2!("invoking {} at {}", llfn, bcx.llbb);
             for &llarg in llargs.iter() {
-                debug!("arg: %x", ::std::cast::transmute(llarg));
+                debug2!("arg: {}", llarg);
             }
         }
         let normal_bcx = sub_block(bcx, "normal return");
@@ -937,11 +935,9 @@ pub fn invoke(bcx: @mut Block, llfn: ValueRef, llargs: ~[ValueRef],
         return (llresult, normal_bcx);
     } else {
         unsafe {
-            debug!("calling %x at %x",
-                   ::std::cast::transmute(llfn),
-                   ::std::cast::transmute(bcx.llbb));
+            debug2!("calling {} at {}", llfn, bcx.llbb);
             for &llarg in llargs.iter() {
-                debug!("arg: %x", ::std::cast::transmute(llarg));
+                debug2!("arg: {}", llarg);
             }
         }
         let llresult = Call(bcx, llfn, llargs, attributes);
@@ -1092,7 +1088,7 @@ pub fn find_bcx_for_scope(bcx: @mut Block, scope_id: ast::NodeId) -> @mut Block
             }
             None => {
                 bcx_sid = match bcx_sid.parent {
-                    None => bcx.tcx().sess.bug(fmt!("no enclosing scope with id %d", scope_id)),
+                    None => bcx.tcx().sess.bug(format!("no enclosing scope with id {}", scope_id)),
                     Some(bcx_par) => bcx_par
                 };
                 bcx_sid.scope
@@ -1161,7 +1157,7 @@ pub fn ignore_lhs(_bcx: @mut Block, local: &ast::Local) -> bool {
 
 pub fn init_local(bcx: @mut Block, local: &ast::Local) -> @mut Block {
 
-    debug!("init_local(bcx=%s, local.id=%?)",
+    debug2!("init_local(bcx={}, local.id={:?})",
            bcx.to_str(), local.id);
     let _indenter = indenter();
 
@@ -1182,7 +1178,7 @@ pub fn init_local(bcx: @mut Block, local: &ast::Local) -> @mut Block {
 
 pub fn trans_stmt(cx: @mut Block, s: &ast::Stmt) -> @mut Block {
     let _icx = push_ctxt("trans_stmt");
-    debug!("trans_stmt(%s)", stmt_to_str(s, cx.tcx().sess.intr()));
+    debug2!("trans_stmt({})", stmt_to_str(s, cx.tcx().sess.intr()));
 
     if cx.sess().asm_comments() {
         add_span_comment(cx, s.span, stmt_to_str(s, cx.ccx().sess.intr()));
@@ -1345,12 +1341,12 @@ pub fn cleanup_and_leave(bcx: @mut Block,
     let mut bcx = bcx;
     let is_lpad = leave == None;
     loop {
-        debug!("cleanup_and_leave: leaving %s", cur.to_str());
+        debug2!("cleanup_and_leave: leaving {}", cur.to_str());
 
         if bcx.sess().trace() {
             trans_trace(
                 bcx, None,
-                (fmt!("cleanup_and_leave(%s)", cur.to_str())).to_managed());
+                (format!("cleanup_and_leave({})", cur.to_str())).to_managed());
         }
 
         let mut cur_scope = cur.scope;
@@ -1419,12 +1415,12 @@ pub fn cleanup_block(bcx: @mut Block, upto: Option<BasicBlockRef>) -> @mut Block
     let mut cur = bcx;
     let mut bcx = bcx;
     loop {
-        debug!("cleanup_block: %s", cur.to_str());
+        debug2!("cleanup_block: {}", cur.to_str());
 
         if bcx.sess().trace() {
             trans_trace(
                 bcx, None,
-                (fmt!("cleanup_block(%s)", cur.to_str())).to_managed());
+                (format!("cleanup_block({})", cur.to_str())).to_managed());
         }
 
         let mut cur_scope = cur.scope;
@@ -1469,7 +1465,7 @@ pub fn with_scope(bcx: @mut Block,
                   f: &fn(@mut Block) -> @mut Block) -> @mut Block {
     let _icx = push_ctxt("with_scope");
 
-    debug!("with_scope(bcx=%s, opt_node_info=%?, name=%s)",
+    debug2!("with_scope(bcx={}, opt_node_info={:?}, name={})",
            bcx.to_str(), opt_node_info, name);
     let _indenter = indenter();
 
@@ -1599,7 +1595,7 @@ pub fn alloc_ty(bcx: @mut Block, t: ty::t, name: &str) -> ValueRef {
     let _icx = push_ctxt("alloc_ty");
     let ccx = bcx.ccx();
     let ty = type_of::type_of(ccx, t);
-    assert!(!ty::type_has_params(t), "Type has params: %s", ty_to_str(ccx.tcx, t));
+    assert!(!ty::type_has_params(t));
     let val = alloca(bcx, ty, name);
     return val;
 }
@@ -1688,8 +1684,8 @@ pub fn new_fn_ctxt_w_id(ccx: @mut CrateContext,
                      -> @mut FunctionContext {
     for p in param_substs.iter() { p.validate(); }
 
-    debug!("new_fn_ctxt_w_id(path=%s, id=%?, \
-            param_substs=%s)",
+    debug2!("new_fn_ctxt_w_id(path={}, id={:?}, \
+            param_substs={})",
            path_str(ccx.sess, path),
            id,
            param_substs.repr(ccx.tcx));
@@ -1802,7 +1798,7 @@ pub fn copy_args_to_allocas(fcx: @mut FunctionContext,
                             args: &[ast::arg],
                             raw_llargs: &[ValueRef],
                             arg_tys: &[ty::t]) -> @mut Block {
-    debug!("copy_args_to_allocas: raw_llargs=%s arg_tys=%s",
+    debug2!("copy_args_to_allocas: raw_llargs={} arg_tys={}",
            raw_llargs.llrepr(fcx.ccx),
            arg_tys.repr(fcx.ccx.tcx));
 
@@ -1926,7 +1922,7 @@ pub fn trans_closure(ccx: @mut CrateContext,
     let _icx = push_ctxt("trans_closure");
     set_uwtable(llfndecl);
 
-    debug!("trans_closure(..., param_substs=%s)",
+    debug2!("trans_closure(..., param_substs={})",
            param_substs.repr(ccx.tcx));
 
     let fcx = new_fn_ctxt_w_id(ccx,
@@ -2006,7 +2002,7 @@ pub fn trans_fn(ccx: @mut CrateContext,
 
     let the_path_str = path_str(ccx.sess, path);
     let _s = StatRecorder::new(ccx, the_path_str);
-    debug!("trans_fn(self_arg=%?, param_substs=%s)",
+    debug2!("trans_fn(self_arg={:?}, param_substs={})",
            self_arg,
            param_substs.repr(ccx.tcx));
     let _icx = push_ctxt("trans_fn");
@@ -2042,7 +2038,7 @@ fn insert_synthetic_type_entries(bcx: @mut Block,
 
     let tcx = bcx.tcx();
     for i in range(0u, fn_args.len()) {
-        debug!("setting type of argument %u (pat node %d) to %s",
+        debug2!("setting type of argument {} (pat node {}) to {}",
                i, fn_args[i].pat.id, bcx.ty_to_str(arg_tys[i]));
 
         let pat_id = fn_args[i].pat.id;
@@ -2141,8 +2137,8 @@ pub fn trans_enum_variant_or_tuple_like_struct<A:IdAndTy>(
     let result_ty = match ty::get(ctor_ty).sty {
         ty::ty_bare_fn(ref bft) => bft.sig.output,
         _ => ccx.sess.bug(
-            fmt!("trans_enum_variant_or_tuple_like_struct: \
-                  unexpected ctor return type %s",
+            format!("trans_enum_variant_or_tuple_like_struct: \
+                  unexpected ctor return type {}",
                  ty_to_str(ccx.tcx, ctor_ty)))
     };
 
@@ -2218,7 +2214,7 @@ pub fn trans_item(ccx: @mut CrateContext, item: &ast::item) {
     let path = match ccx.tcx.items.get_copy(&item.id) {
         ast_map::node_item(_, p) => p,
         // tjc: ?
-        _ => fail!("trans_item"),
+        _ => fail2!("trans_item"),
     };
     match item.node {
       ast::item_fn(ref decl, purity, _abis, ref generics, ref body) => {
@@ -2360,7 +2356,7 @@ pub fn register_fn(ccx: @mut CrateContext,
             assert!(f.abis.is_rust() || f.abis.is_intrinsic());
             f
         }
-        _ => fail!("expected bare rust fn or an intrinsic")
+        _ => fail2!("expected bare rust fn or an intrinsic")
     };
 
     let llfn = decl_rust_fn(ccx, f.sig.inputs, f.sig.output, sym);
@@ -2376,7 +2372,7 @@ pub fn register_fn_llvmty(ccx: @mut CrateContext,
                           cc: lib::llvm::CallConv,
                           fn_ty: Type)
                           -> ValueRef {
-    debug!("register_fn_fuller creating fn for item %d with path %s",
+    debug2!("register_fn_fuller creating fn for item {} with path {}",
            node_id,
            ast_map::path_to_str(item_path(ccx, &node_id), token::get_ident_interner()));
 
@@ -2455,7 +2451,7 @@ pub fn create_entry_wrapper(ccx: @mut CrateContext,
                 };
                 (start_fn, args)
             } else {
-                debug!("using user-defined start fn");
+                debug2!("using user-defined start fn");
                 let args = ~[
                     C_null(Type::opaque_box(ccx).ptr_to()),
                     llvm::LLVMGetParam(llfn, 0 as c_uint),
@@ -2503,7 +2499,7 @@ fn exported_name(ccx: &mut CrateContext, path: path, ty: ty::t, attrs: &[ast::At
 }
 
 pub fn get_item_val(ccx: @mut CrateContext, id: ast::NodeId) -> ValueRef {
-    debug!("get_item_val(id=`%?`)", id);
+    debug2!("get_item_val(id=`{:?}`)", id);
 
     let val = ccx.item_vals.find_copy(&id);
     match val {
@@ -2525,10 +2521,10 @@ pub fn get_item_val(ccx: @mut CrateContext, id: ast::NodeId) -> ValueRef {
                             // we need to get the symbol from csearch instead of
                             // using the current crate's name/version
                             // information in the hash of the symbol
-                            debug!("making %s", sym);
+                            debug2!("making {}", sym);
                             let sym = match ccx.external_srcs.find(&i.id) {
                                 Some(&did) => {
-                                    debug!("but found in other crate...");
+                                    debug2!("but found in other crate...");
                                     csearch::get_symbol(ccx.sess.cstore, did)
                                 }
                                 None => sym
@@ -2579,7 +2575,7 @@ pub fn get_item_val(ccx: @mut CrateContext, id: ast::NodeId) -> ValueRef {
                                 }
 
                                 if !inlineable {
-                                    debug!("%s not inlined", sym);
+                                    debug2!("{} not inlined", sym);
                                     ccx.non_inlineable_statics.insert(id);
                                 }
                                 ccx.item_symbols.insert(i.id, sym);
@@ -2600,7 +2596,7 @@ pub fn get_item_val(ccx: @mut CrateContext, id: ast::NodeId) -> ValueRef {
                             llfn
                         }
 
-                        _ => fail!("get_item_val: weird result in table")
+                        _ => fail2!("get_item_val: weird result in table")
                     };
 
                     match (attr::first_attr_value_str_by_name(i.attrs, "link_section")) {
@@ -2616,7 +2612,7 @@ pub fn get_item_val(ccx: @mut CrateContext, id: ast::NodeId) -> ValueRef {
                 }
 
                 ast_map::node_trait_method(trait_method, _, pth) => {
-                    debug!("get_item_val(): processing a node_trait_method");
+                    debug2!("get_item_val(): processing a node_trait_method");
                     match *trait_method {
                         ast::required(_) => {
                             ccx.sess.bug("unexpected variant: required trait method in \
@@ -2673,11 +2669,11 @@ pub fn get_item_val(ccx: @mut CrateContext, id: ast::NodeId) -> ValueRef {
                                 ast::item_enum(_, _) => {
                                     register_fn(ccx, (*v).span, sym, id, ty)
                                 }
-                                _ => fail!("node_variant, shouldn't happen")
+                                _ => fail2!("node_variant, shouldn't happen")
                             };
                         }
                         ast::struct_variant_kind(_) => {
-                            fail!("struct variant kind unexpected in get_item_val")
+                            fail2!("struct variant kind unexpected in get_item_val")
                         }
                     }
                     set_inline_hint(llfn);
@@ -2704,7 +2700,7 @@ pub fn get_item_val(ccx: @mut CrateContext, id: ast::NodeId) -> ValueRef {
                 }
 
                 ref variant => {
-                    ccx.sess.bug(fmt!("get_item_val(): unexpected variant: %?",
+                    ccx.sess.bug(format!("get_item_val(): unexpected variant: {:?}",
                                  variant))
                 }
             };
@@ -2959,7 +2955,7 @@ pub fn decl_crate_map(sess: session::Session, mapmeta: LinkMeta,
     let cstore = sess.cstore;
     while cstore::have_crate_data(cstore, n_subcrates) { n_subcrates += 1; }
     let mapname = if *sess.building_library {
-        fmt!("%s_%s_%s", mapmeta.name, mapmeta.vers, mapmeta.extras_hash)
+        format!("{}_{}_{}", mapmeta.name, mapmeta.vers, mapmeta.extras_hash)
     } else {
         ~"toplevel"
     };
@@ -2988,7 +2984,7 @@ pub fn fill_crate_map(ccx: &mut CrateContext, map: ValueRef) {
     let cstore = ccx.sess.cstore;
     while cstore::have_crate_data(cstore, i) {
         let cdata = cstore::get_crate_data(cstore, i);
-        let nm = fmt!("_rust_crate_map_%s_%s_%s",
+        let nm = format!("_rust_crate_map_{}_{}_{}",
                       cdata.name,
                       cstore::get_crate_vers(cstore, i),
                       cstore::get_crate_hash(cstore, i));
diff --git a/src/librustc/middle/trans/build.rs b/src/librustc/middle/trans/build.rs
index 1cad4f8a93f..1754741a1f4 100644
--- a/src/librustc/middle/trans/build.rs
+++ b/src/librustc/middle/trans/build.rs
@@ -29,7 +29,7 @@ pub fn terminate(cx: &mut Block, _: &str) {
 
 pub fn check_not_terminated(cx: &Block) {
     if cx.terminated {
-        fail!("already terminated!");
+        fail2!("already terminated!");
     }
 }
 
@@ -117,7 +117,7 @@ pub fn Invoke(cx: @mut Block,
     }
     check_not_terminated(cx);
     terminate(cx, "Invoke");
-    debug!("Invoke(%s with arguments (%s))",
+    debug2!("Invoke({} with arguments ({}))",
            cx.val_to_str(Fn),
            Args.map(|a| cx.val_to_str(*a)).connect(", "));
     B(cx).invoke(Fn, Args, Then, Catch, attributes)
diff --git a/src/librustc/middle/trans/builder.rs b/src/librustc/middle/trans/builder.rs
index d7a4dbb3510..febe4de730d 100644
--- a/src/librustc/middle/trans/builder.rs
+++ b/src/librustc/middle/trans/builder.rs
@@ -476,7 +476,7 @@ impl Builder {
     }
 
     pub fn store(&self, val: ValueRef, ptr: ValueRef) {
-        debug!("Store %s -> %s",
+        debug2!("Store {} -> {}",
                self.ccx.tn.val_to_str(val),
                self.ccx.tn.val_to_str(ptr));
         assert!(is_not_null(self.llbuilder));
@@ -487,7 +487,7 @@ impl Builder {
     }
 
     pub fn atomic_store(&self, val: ValueRef, ptr: ValueRef, order: AtomicOrdering) {
-        debug!("Store %s -> %s",
+        debug2!("Store {} -> {}",
                self.ccx.tn.val_to_str(val),
                self.ccx.tn.val_to_str(ptr));
         self.count_insn("store.atomic");
@@ -725,8 +725,8 @@ impl Builder {
 
     pub fn add_span_comment(&self, sp: Span, text: &str) {
         if self.ccx.sess.asm_comments() {
-            let s = fmt!("%s (%s)", text, self.ccx.sess.codemap.span_to_str(sp));
-            debug!("%s", s);
+            let s = format!("{} ({})", text, self.ccx.sess.codemap.span_to_str(sp));
+            debug2!("{}", s);
             self.add_comment(s);
         }
     }
@@ -734,7 +734,7 @@ impl Builder {
     pub fn add_comment(&self, text: &str) {
         if self.ccx.sess.asm_comments() {
             let sanitized = text.replace("$", "");
-            let comment_text = fmt!("# %s", sanitized.replace("\n", "\n\t# "));
+            let comment_text = format!("\\# {}", sanitized.replace("\n", "\n\t# "));
             self.count_insn("inlineasm");
             let asm = do comment_text.with_c_str |c| {
                 unsafe {
@@ -758,11 +758,11 @@ impl Builder {
                          else          { lib::llvm::False };
 
         let argtys = do inputs.map |v| {
-            debug!("Asm Input Type: %?", self.ccx.tn.val_to_str(*v));
+            debug2!("Asm Input Type: {:?}", self.ccx.tn.val_to_str(*v));
             val_ty(*v)
         };
 
-        debug!("Asm Output Type: %?", self.ccx.tn.type_to_str(output));
+        debug2!("Asm Output Type: {:?}", self.ccx.tn.type_to_str(output));
         let fty = Type::func(argtys, &output);
         unsafe {
             let v = llvm::LLVMInlineAsm(
diff --git a/src/librustc/middle/trans/cabi_arm.rs b/src/librustc/middle/trans/cabi_arm.rs
index 19f0b9b78eb..2cba0615310 100644
--- a/src/librustc/middle/trans/cabi_arm.rs
+++ b/src/librustc/middle/trans/cabi_arm.rs
@@ -49,7 +49,7 @@ fn ty_align(ty: Type) -> uint {
             let elt = ty.element_type();
             ty_align(elt)
         }
-        _ => fail!("ty_align: unhandled type")
+        _ => fail2!("ty_align: unhandled type")
     }
 }
 
@@ -79,7 +79,7 @@ fn ty_size(ty: Type) -> uint {
             let eltsz = ty_size(elt);
             len * eltsz
         }
-        _ => fail!("ty_size: unhandled type")
+        _ => fail2!("ty_size: unhandled type")
     }
 }
 
diff --git a/src/librustc/middle/trans/cabi_mips.rs b/src/librustc/middle/trans/cabi_mips.rs
index 4577bf11b84..3d11c3dafb2 100644
--- a/src/librustc/middle/trans/cabi_mips.rs
+++ b/src/librustc/middle/trans/cabi_mips.rs
@@ -51,7 +51,7 @@ fn ty_align(ty: Type) -> uint {
             let elt = ty.element_type();
             ty_align(elt)
         }
-        _ => fail!("ty_size: unhandled type")
+        _ => fail2!("ty_size: unhandled type")
     }
 }
 
@@ -81,7 +81,7 @@ fn ty_size(ty: Type) -> uint {
             let eltsz = ty_size(elt);
             len * eltsz
         }
-        _ => fail!("ty_size: unhandled type")
+        _ => fail2!("ty_size: unhandled type")
     }
 }
 
diff --git a/src/librustc/middle/trans/cabi_x86_64.rs b/src/librustc/middle/trans/cabi_x86_64.rs
index 17936687841..9f098fe3cc1 100644
--- a/src/librustc/middle/trans/cabi_x86_64.rs
+++ b/src/librustc/middle/trans/cabi_x86_64.rs
@@ -112,7 +112,7 @@ fn classify_ty(ty: Type) -> ~[RegClass] {
                 let elt = ty.element_type();
                 ty_align(elt)
             }
-            _ => fail!("ty_size: unhandled type")
+            _ => fail2!("ty_size: unhandled type")
         }
     }
 
@@ -141,7 +141,7 @@ fn classify_ty(ty: Type) -> ~[RegClass] {
                 let eltsz = ty_size(elt);
                 len * eltsz
             }
-            _ => fail!("ty_size: unhandled type")
+            _ => fail2!("ty_size: unhandled type")
         }
     }
 
@@ -232,7 +232,7 @@ fn classify_ty(ty: Type) -> ~[RegClass] {
                     i += 1u;
                 }
             }
-            _ => fail!("classify: unhandled type")
+            _ => fail2!("classify: unhandled type")
         }
     }
 
@@ -325,7 +325,7 @@ fn llreg_ty(cls: &[RegClass]) -> Type {
             SSEDs => {
                 tys.push(Type::f64());
             }
-            _ => fail!("llregtype: unhandled class")
+            _ => fail2!("llregtype: unhandled class")
         }
         i += 1u;
     }
diff --git a/src/librustc/middle/trans/callee.rs b/src/librustc/middle/trans/callee.rs
index a3788d7cbde..c1a9f764962 100644
--- a/src/librustc/middle/trans/callee.rs
+++ b/src/librustc/middle/trans/callee.rs
@@ -79,7 +79,7 @@ pub struct Callee {
 
 pub fn trans(bcx: @mut Block, expr: &ast::Expr) -> Callee {
     let _icx = push_ctxt("trans_callee");
-    debug!("callee::trans(expr=%s)", expr.repr(bcx.tcx()));
+    debug2!("callee::trans(expr={})", expr.repr(bcx.tcx()));
 
     // pick out special kinds of expressions that can be called:
     match expr.node {
@@ -105,7 +105,7 @@ pub fn trans(bcx: @mut Block, expr: &ast::Expr) -> Callee {
             _ => {
                 bcx.tcx().sess.span_bug(
                     expr.span,
-                    fmt!("Type of callee is neither bare-fn nor closure: %s",
+                    format!("Type of callee is neither bare-fn nor closure: {}",
                          bcx.ty_to_str(datum.ty)));
             }
         }
@@ -153,7 +153,7 @@ pub fn trans(bcx: @mut Block, expr: &ast::Expr) -> Callee {
             ast::DefSelfTy(*) | ast::DefMethod(*) => {
                 bcx.tcx().sess.span_bug(
                     ref_expr.span,
-                    fmt!("Cannot translate def %? \
+                    format!("Cannot translate def {:?} \
                           to a callable thing!", def));
             }
         }
@@ -180,7 +180,7 @@ pub fn trans_fn_ref(bcx: @mut Block,
 
     let type_params = node_id_type_params(bcx, ref_id);
     let vtables = node_vtables(bcx, ref_id);
-    debug!("trans_fn_ref(def_id=%s, ref_id=%?, type_params=%s, vtables=%s)",
+    debug2!("trans_fn_ref(def_id={}, ref_id={:?}, type_params={}, vtables={})",
            def_id.repr(bcx.tcx()), ref_id, type_params.repr(bcx.tcx()),
            vtables.repr(bcx.tcx()));
     trans_fn_ref_with_vtables(bcx, def_id, ref_id, type_params, vtables)
@@ -266,8 +266,8 @@ pub fn trans_fn_ref_with_vtables(
     let ccx = bcx.ccx();
     let tcx = ccx.tcx;
 
-    debug!("trans_fn_ref_with_vtables(bcx=%s, def_id=%s, ref_id=%?, \
-            type_params=%s, vtables=%s)",
+    debug2!("trans_fn_ref_with_vtables(bcx={}, def_id={}, ref_id={:?}, \
+            type_params={}, vtables={})",
            bcx.to_str(),
            def_id.repr(bcx.tcx()),
            ref_id,
@@ -329,11 +329,11 @@ pub fn trans_fn_ref_with_vtables(
                 resolve_default_method_vtables(bcx, impl_id,
                                                method, &substs, vtables);
 
-            debug!("trans_fn_with_vtables - default method: \
-                    substs = %s, trait_subst = %s, \
-                    first_subst = %s, new_subst = %s, \
-                    vtables = %s, \
-                    self_vtable = %s, param_vtables = %s",
+            debug2!("trans_fn_with_vtables - default method: \
+                    substs = {}, trait_subst = {}, \
+                    first_subst = {}, new_subst = {}, \
+                    vtables = {}, \
+                    self_vtable = {}, param_vtables = {}",
                    substs.repr(tcx), trait_ref.substs.repr(tcx),
                    first_subst.repr(tcx), new_substs.repr(tcx),
                    vtables.repr(tcx),
@@ -365,7 +365,7 @@ pub fn trans_fn_ref_with_vtables(
         let map_node = session::expect(
             ccx.sess,
             ccx.tcx.items.find(&def_id.node),
-            || fmt!("local item should be in ast map"));
+            || format!("local item should be in ast map"));
 
         match *map_node {
             ast_map::node_foreign_item(_, abis, _, _) => {
@@ -472,7 +472,7 @@ pub fn trans_method_call(in_cx: @mut Block,
                          dest: expr::Dest)
                          -> @mut Block {
     let _icx = push_ctxt("trans_method_call");
-    debug!("trans_method_call(call_ex=%s, rcvr=%s)",
+    debug2!("trans_method_call(call_ex={}, rcvr={})",
            call_ex.repr(in_cx.tcx()),
            rcvr.repr(in_cx.tcx()));
     trans_call_inner(
@@ -483,7 +483,7 @@ pub fn trans_method_call(in_cx: @mut Block,
         |cx| {
             match cx.ccx().maps.method_map.find_copy(&call_ex.id) {
                 Some(origin) => {
-                    debug!("origin for %s: %s",
+                    debug2!("origin for {}: {}",
                            call_ex.repr(in_cx.tcx()),
                            origin.repr(in_cx.tcx()));
 
@@ -562,7 +562,7 @@ pub fn trans_lang_call_with_type_params(bcx: @mut Block,
                                                       substituted);
                     new_llval = PointerCast(callee.bcx, fn_data.llfn, llfnty);
                 }
-                _ => fail!()
+                _ => fail2!()
             }
             Callee { bcx: callee.bcx, data: Fn(FnData { llfn: new_llval }) }
         },
@@ -840,7 +840,7 @@ pub fn trans_arg_expr(bcx: @mut Block,
     let _icx = push_ctxt("trans_arg_expr");
     let ccx = bcx.ccx();
 
-    debug!("trans_arg_expr(formal_arg_ty=(%s), self_mode=%?, arg_expr=%s)",
+    debug2!("trans_arg_expr(formal_arg_ty=({}), self_mode={:?}, arg_expr={})",
            formal_arg_ty.repr(bcx.tcx()),
            self_mode,
            arg_expr.repr(bcx.tcx()));
@@ -850,7 +850,7 @@ pub fn trans_arg_expr(bcx: @mut Block,
     let arg_datum = arg_datumblock.datum;
     let bcx = arg_datumblock.bcx;
 
-    debug!("   arg datum: %s", arg_datum.to_str(bcx.ccx()));
+    debug2!("   arg datum: {}", arg_datum.to_str(bcx.ccx()));
 
     let mut val;
     if ty::type_is_bot(arg_datum.ty) {
@@ -890,11 +890,11 @@ pub fn trans_arg_expr(bcx: @mut Block,
 
                 val = match self_mode {
                     ty::ByRef => {
-                        debug!("by ref arg with type %s", bcx.ty_to_str(arg_datum.ty));
+                        debug2!("by ref arg with type {}", bcx.ty_to_str(arg_datum.ty));
                         arg_datum.to_ref_llval(bcx)
                     }
                     ty::ByCopy => {
-                        debug!("by copy arg with type %s", bcx.ty_to_str(arg_datum.ty));
+                        debug2!("by copy arg with type {}", bcx.ty_to_str(arg_datum.ty));
                         arg_datum.to_appropriate_llval(bcx)
                     }
                 }
@@ -904,12 +904,12 @@ pub fn trans_arg_expr(bcx: @mut Block,
         if formal_arg_ty != arg_datum.ty {
             // this could happen due to e.g. subtyping
             let llformal_arg_ty = type_of::type_of_explicit_arg(ccx, formal_arg_ty);
-            debug!("casting actual type (%s) to match formal (%s)",
+            debug2!("casting actual type ({}) to match formal ({})",
                    bcx.val_to_str(val), bcx.llty_str(llformal_arg_ty));
             val = PointerCast(bcx, val, llformal_arg_ty);
         }
     }
 
-    debug!("--- trans_arg_expr passing %s", bcx.val_to_str(val));
+    debug2!("--- trans_arg_expr passing {}", bcx.val_to_str(val));
     return rslt(bcx, val);
 }
diff --git a/src/librustc/middle/trans/closure.rs b/src/librustc/middle/trans/closure.rs
index b5b181e22a6..875be5d3af5 100644
--- a/src/librustc/middle/trans/closure.rs
+++ b/src/librustc/middle/trans/closure.rs
@@ -127,7 +127,7 @@ impl EnvAction {
 
 impl EnvValue {
     pub fn to_str(&self, ccx: &CrateContext) -> ~str {
-        fmt!("%s(%s)", self.action.to_str(), self.datum.to_str(ccx))
+        format!("{}({})", self.action.to_str(), self.datum.to_str(ccx))
     }
 }
 
@@ -151,7 +151,7 @@ pub fn mk_closure_tys(tcx: ty::ctxt,
         }
     });
     let cdata_ty = ty::mk_tup(tcx, bound_tys);
-    debug!("cdata_ty=%s", ty_to_str(tcx, cdata_ty));
+    debug2!("cdata_ty={}", ty_to_str(tcx, cdata_ty));
     return cdata_ty;
 }
 
@@ -224,15 +224,15 @@ pub fn store_environment(bcx: @mut Block,
     let Result {bcx: bcx, val: llbox} = allocate_cbox(bcx, sigil, cdata_ty);
 
     let llbox = PointerCast(bcx, llbox, llboxptr_ty);
-    debug!("tuplify_box_ty = %s", ty_to_str(tcx, cbox_ty));
+    debug2!("tuplify_box_ty = {}", ty_to_str(tcx, cbox_ty));
 
     // Copy expr values into boxed bindings.
     let mut bcx = bcx;
     for (i, bv) in bound_values.iter().enumerate() {
-        debug!("Copy %s into closure", bv.to_str(ccx));
+        debug2!("Copy {} into closure", bv.to_str(ccx));
 
         if ccx.sess.asm_comments() {
-            add_comment(bcx, fmt!("Copy %s into closure",
+            add_comment(bcx, format!("Copy {} into closure",
                                   bv.to_str(ccx)));
         }
 
@@ -268,7 +268,7 @@ pub fn build_closure(bcx0: @mut Block,
     // Package up the captured upvars
     let mut env_vals = ~[];
     for cap_var in cap_vars.iter() {
-        debug!("Building closure: captured variable %?", *cap_var);
+        debug2!("Building closure: captured variable {:?}", *cap_var);
         let datum = expr::trans_local_var(bcx, cap_var.def);
         match cap_var.mode {
             moves::CapRef => {
@@ -384,7 +384,7 @@ pub fn trans_expr_fn(bcx: @mut Block,
     let fty = node_id_type(bcx, outer_id);
     let f = match ty::get(fty).sty {
         ty::ty_closure(ref f) => f,
-        _ => fail!("expected closure")
+        _ => fail2!("expected closure")
     };
 
     let sub_path = vec::append_one(bcx.fcx.path.clone(),
diff --git a/src/librustc/middle/trans/common.rs b/src/librustc/middle/trans/common.rs
index f030fb4996b..4d46ae385eb 100644
--- a/src/librustc/middle/trans/common.rs
+++ b/src/librustc/middle/trans/common.rs
@@ -169,7 +169,7 @@ impl param_substs {
 }
 
 fn param_substs_to_str(this: &param_substs, tcx: ty::ctxt) -> ~str {
-    fmt!("param_substs {tys:%s, vtables:%s}",
+    format!("param_substs \\{tys:{}, vtables:{}\\}",
          this.tys.repr(tcx),
          this.vtables.repr(tcx))
 }
@@ -436,7 +436,7 @@ pub fn add_clean(bcx: @mut Block, val: ValueRef, t: ty::t) {
         return
     }
 
-    debug!("add_clean(%s, %s, %s)", bcx.to_str(), bcx.val_to_str(val), t.repr(bcx.tcx()));
+    debug2!("add_clean({}, {}, {})", bcx.to_str(), bcx.val_to_str(val), t.repr(bcx.tcx()));
 
     let cleanup_type = cleanup_type(bcx.tcx(), t);
     do in_scope_cx(bcx, None) |scope_info| {
@@ -451,7 +451,7 @@ pub fn add_clean(bcx: @mut Block, val: ValueRef, t: ty::t) {
 
 pub fn add_clean_temp_immediate(cx: @mut Block, val: ValueRef, ty: ty::t) {
     if !ty::type_needs_drop(cx.tcx(), ty) { return; }
-    debug!("add_clean_temp_immediate(%s, %s, %s)",
+    debug2!("add_clean_temp_immediate({}, {}, {})",
            cx.to_str(), cx.val_to_str(val),
            ty.repr(cx.tcx()));
     let cleanup_type = cleanup_type(cx.tcx(), ty);
@@ -480,7 +480,7 @@ pub fn add_clean_temp_mem_in_scope(bcx: @mut Block,
 pub fn add_clean_temp_mem_in_scope_(bcx: @mut Block, scope_id: Option<ast::NodeId>,
                                     val: ValueRef, t: ty::t) {
     if !ty::type_needs_drop(bcx.tcx(), t) { return; }
-    debug!("add_clean_temp_mem(%s, %s, %s)",
+    debug2!("add_clean_temp_mem({}, {}, {})",
            bcx.to_str(), bcx.val_to_str(val),
            t.repr(bcx.tcx()));
     let cleanup_type = cleanup_type(bcx.tcx(), t);
@@ -509,7 +509,7 @@ pub fn add_clean_return_to_mut(bcx: @mut Block,
     //! box was frozen initially. Here, both `frozen_val_ref` and
     //! `bits_val_ref` are in fact pointers to stack slots.
 
-    debug!("add_clean_return_to_mut(%s, %s, %s)",
+    debug2!("add_clean_return_to_mut({}, {}, {})",
            bcx.to_str(),
            bcx.val_to_str(frozen_val_ref),
            bcx.val_to_str(bits_val_ref));
@@ -705,8 +705,8 @@ impl Block {
         match self.tcx().def_map.find(&nid) {
             Some(&v) => v,
             None => {
-                self.tcx().sess.bug(fmt!(
-                    "No def associated with node id %?", nid));
+                self.tcx().sess.bug(format!(
+                    "No def associated with node id {:?}", nid));
             }
         }
     }
@@ -726,8 +726,8 @@ impl Block {
     pub fn to_str(&self) -> ~str {
         unsafe {
             match self.node_info {
-                Some(node_info) => fmt!("[block %d]", node_info.id),
-                None => fmt!("[block %x]", transmute(&*self)),
+                Some(node_info) => format!("[block {}]", node_info.id),
+                None => format!("[block {}]", transmute::<&Block, *Block>(self)),
             }
         }
     }
@@ -763,7 +763,7 @@ pub fn in_scope_cx(cx: @mut Block, scope_id: Option<ast::NodeId>, f: &fn(si: &mu
             Some(inf) => match scope_id {
                 Some(wanted) => match inf.node_info {
                     Some(NodeInfo { id: actual, _ }) if wanted == actual => {
-                        debug!("in_scope_cx: selected cur=%s (cx=%s)",
+                        debug2!("in_scope_cx: selected cur={} (cx={})",
                                cur.to_str(), cx.to_str());
                         f(inf);
                         return;
@@ -771,7 +771,7 @@ pub fn in_scope_cx(cx: @mut Block, scope_id: Option<ast::NodeId>, f: &fn(si: &mu
                     _ => inf.parent,
                 },
                 None => {
-                    debug!("in_scope_cx: selected cur=%s (cx=%s)",
+                    debug2!("in_scope_cx: selected cur={} (cx={})",
                            cur.to_str(), cx.to_str());
                     f(inf);
                     return;
@@ -788,7 +788,7 @@ pub fn in_scope_cx(cx: @mut Block, scope_id: Option<ast::NodeId>, f: &fn(si: &mu
 pub fn block_parent(cx: @mut Block) -> @mut Block {
     match cx.parent {
       Some(b) => b,
-      None    => cx.sess().bug(fmt!("block_parent called on root block %?",
+      None    => cx.sess().bug(format!("block_parent called on root block {:?}",
                                    cx))
     }
 }
@@ -881,7 +881,7 @@ pub fn C_cstr(cx: &mut CrateContext, s: @str) -> ValueRef {
         };
 
         let gsym = token::gensym("str");
-        let g = do fmt!("str%u", gsym).with_c_str |buf| {
+        let g = do format!("str{}", gsym).with_c_str |buf| {
             llvm::LLVMAddGlobal(cx.llmod, val_ty(sc).to_ref(), buf)
         };
         llvm::LLVMSetInitializer(g, sc);
@@ -964,7 +964,7 @@ pub fn const_get_elt(cx: &CrateContext, v: ValueRef, us: &[c_uint])
             llvm::LLVMConstExtractValue(v, p, len as c_uint)
         };
 
-        debug!("const_get_elt(v=%s, us=%?, r=%s)",
+        debug2!("const_get_elt(v={}, us={:?}, r={})",
                cx.tn.val_to_str(v), us, cx.tn.val_to_str(r));
 
         return r;
@@ -1115,7 +1115,7 @@ pub fn node_id_type_params(bcx: &mut Block, id: ast::NodeId) -> ~[ty::t] {
 
     if !params.iter().all(|t| !ty::type_needs_infer(*t)) {
         bcx.sess().bug(
-            fmt!("Type parameters for node %d include inference types: %s",
+            format!("Type parameters for node {} include inference types: {}",
                  id, params.map(|t| bcx.ty_to_str(*t)).connect(",")));
     }
 
@@ -1193,7 +1193,7 @@ pub fn resolve_vtable_under_param_substs(tcx: ty::ctxt,
                     find_vtable(tcx, substs, n_param, n_bound)
                 }
                 _ => {
-                    tcx.sess.bug(fmt!(
+                    tcx.sess.bug(format!(
                         "resolve_vtable_under_param_substs: asked to lookup \
                          but no vtables in the fn_ctxt!"))
                 }
@@ -1207,7 +1207,7 @@ pub fn find_vtable(tcx: ty::ctxt,
                    n_param: typeck::param_index,
                    n_bound: uint)
                    -> typeck::vtable_origin {
-    debug!("find_vtable(n_param=%?, n_bound=%u, ps=%s)",
+    debug2!("find_vtable(n_param={:?}, n_bound={}, ps={})",
            n_param, n_bound, ps.repr(tcx));
 
     let param_bounds = match n_param {
@@ -1248,7 +1248,7 @@ pub fn langcall(bcx: @mut Block, span: Option<Span>, msg: &str,
     match bcx.tcx().lang_items.require(li) {
         Ok(id) => id,
         Err(s) => {
-            let msg = fmt!("%s %s", msg, s);
+            let msg = format!("{} {}", msg, s);
             match span {
                 Some(span) => { bcx.tcx().sess.span_fatal(span, msg); }
                 None => { bcx.tcx().sess.fatal(msg); }
diff --git a/src/librustc/middle/trans/consts.rs b/src/librustc/middle/trans/consts.rs
index 7d208c896b7..aa566314386 100644
--- a/src/librustc/middle/trans/consts.rs
+++ b/src/librustc/middle/trans/consts.rs
@@ -52,7 +52,7 @@ pub fn const_lit(cx: &mut CrateContext, e: &ast::Expr, lit: ast::lit)
             C_integral(Type::uint_from_ty(cx, t), i as u64, false)
           }
           _ => cx.sess.span_bug(lit.span,
-                   fmt!("integer literal has type %s (expected int or uint)",
+                   format!("integer literal has type {} (expected int or uint)",
                         ty_to_str(cx.tcx, lit_int_ty)))
         }
       }
@@ -144,14 +144,14 @@ fn const_deref(cx: &mut CrateContext, v: ValueRef, t: ty::t, explicit: bool)
                     const_deref_newtype(cx, v, t)
                 }
                 _ => {
-                    cx.sess.bug(fmt!("Unexpected dereferenceable type %s",
+                    cx.sess.bug(format!("Unexpected dereferenceable type {}",
                                      ty_to_str(cx.tcx, t)))
                 }
             };
             (dv, mt.ty)
         }
         None => {
-            cx.sess.bug(fmt!("Can't dereference const of type %s",
+            cx.sess.bug(format!("Can't dereference const of type {}",
                              ty_to_str(cx.tcx, t)))
         }
     }
@@ -189,8 +189,8 @@ pub fn const_expr(cx: @mut CrateContext, e: &ast::Expr) -> (ValueRef, bool) {
             llconst = C_struct([llconst, C_null(Type::opaque_box(cx).ptr_to())])
         }
         Some(@ty::AutoAddEnv(ref r, ref s)) => {
-            cx.sess.span_bug(e.span, fmt!("unexpected static function: \
-                                           region %? sigil %?", *r, *s))
+            cx.sess.span_bug(e.span, format!("unexpected static function: \
+                                           region {:?} sigil {:?}", *r, *s))
         }
         Some(@ty::AutoDerefRef(ref adj)) => {
             let mut ty = ety;
@@ -234,8 +234,8 @@ pub fn const_expr(cx: @mut CrateContext, e: &ast::Expr) -> (ValueRef, bool) {
                         }
                         _ => {
                             cx.sess.span_bug(e.span,
-                                             fmt!("unimplemented const \
-                                                   autoref %?", autoref))
+                                             format!("unimplemented const \
+                                                   autoref {:?}", autoref))
                         }
                     }
                 }
@@ -253,7 +253,7 @@ pub fn const_expr(cx: @mut CrateContext, e: &ast::Expr) -> (ValueRef, bool) {
             llvm::LLVMDumpValue(llconst);
             llvm::LLVMDumpValue(C_undef(llty));
         }
-        cx.sess.bug(fmt!("const %s of type %s has size %u instead of %u",
+        cx.sess.bug(format!("const {} of type {} has size {} instead of {}",
                          e.repr(cx.tcx), ty_to_str(cx.tcx, ety),
                          csize, tsize));
     }
diff --git a/src/librustc/middle/trans/context.rs b/src/librustc/middle/trans/context.rs
index 36757374b0b..d2a3557d85b 100644
--- a/src/librustc/middle/trans/context.rs
+++ b/src/librustc/middle/trans/context.rs
@@ -252,7 +252,7 @@ impl CrateContext {
     pub fn const_inbounds_gepi(&self,
                                pointer: ValueRef,
                                indices: &[uint]) -> ValueRef {
-        debug!("const_inbounds_gepi: pointer=%s indices=%?",
+        debug2!("const_inbounds_gepi: pointer={} indices={:?}",
                self.tn.val_to_str(pointer), indices);
         let v: ~[ValueRef] =
             indices.iter().map(|i| C_i32(*i as i32)).collect();
diff --git a/src/librustc/middle/trans/controlflow.rs b/src/librustc/middle/trans/controlflow.rs
index 73e7a6745fb..105cb6e5606 100644
--- a/src/librustc/middle/trans/controlflow.rs
+++ b/src/librustc/middle/trans/controlflow.rs
@@ -50,7 +50,7 @@ pub fn trans_if(bcx: @mut Block,
             els: Option<@ast::Expr>,
             dest: expr::Dest)
          -> @mut Block {
-    debug!("trans_if(bcx=%s, cond=%s, thn=%?, dest=%s)",
+    debug2!("trans_if(bcx={}, cond={}, thn={:?}, dest={})",
            bcx.to_str(), bcx.expr_to_str(cond), thn.id,
            dest.to_str(bcx.ccx()));
     let _indenter = indenter();
@@ -119,7 +119,7 @@ pub fn trans_if(bcx: @mut Block,
       }
     };
 
-    debug!("then_bcx_in=%s, else_bcx_in=%s",
+    debug2!("then_bcx_in={}, else_bcx_in={}",
            then_bcx_in.to_str(), else_bcx_in.to_str());
 
     CondBr(bcx, cond_val, then_bcx_in.llbb, else_bcx_in.llbb);
diff --git a/src/librustc/middle/trans/datum.rs b/src/librustc/middle/trans/datum.rs
index e48174b04f8..78422159126 100644
--- a/src/librustc/middle/trans/datum.rs
+++ b/src/librustc/middle/trans/datum.rs
@@ -242,7 +242,7 @@ impl Datum {
                           action: CopyAction,
                           datum: Datum)
                           -> @mut Block {
-        debug!("store_to_datum(self=%s, action=%?, datum=%s)",
+        debug2!("store_to_datum(self={}, action={:?}, datum={})",
                self.to_str(bcx.ccx()), action, datum.to_str(bcx.ccx()));
         assert!(datum.mode.is_by_ref());
         self.store_to(bcx, action, datum.val)
@@ -275,7 +275,7 @@ impl Datum {
             return bcx;
         }
 
-        debug!("copy_to(self=%s, action=%?, dst=%s)",
+        debug2!("copy_to(self={}, action={:?}, dst={})",
                self.to_str(bcx.ccx()), action, bcx.val_to_str(dst));
 
         // Watch out for the case where we are writing the copying the
@@ -340,7 +340,7 @@ impl Datum {
         let _icx = push_ctxt("move_to");
         let mut bcx = bcx;
 
-        debug!("move_to(self=%s, action=%?, dst=%s)",
+        debug2!("move_to(self={}, action={:?}, dst={})",
                self.to_str(bcx.ccx()), action, bcx.val_to_str(dst));
 
         if ty::type_is_voidish(self.ty) {
@@ -380,7 +380,7 @@ impl Datum {
             }
             ByRef(ZeroMem) => {
                 bcx.tcx().sess.bug(
-                    fmt!("Cannot add clean to a 'zero-mem' datum"));
+                    format!("Cannot add clean to a 'zero-mem' datum"));
             }
         }
     }
@@ -404,7 +404,7 @@ impl Datum {
     }
 
     pub fn to_str(&self, ccx: &CrateContext) -> ~str {
-        fmt!("Datum { val=%s, ty=%s, mode=%? }",
+        format!("Datum \\{ val={}, ty={}, mode={:?} \\}",
              ccx.tn.val_to_str(self.val),
              ty_to_str(ccx.tcx, self.ty),
              self.mode)
@@ -573,8 +573,8 @@ impl Datum {
                 (unboxed_vec_ty, true)
             }
             _ => {
-                bcx.tcx().sess.bug(fmt!(
-                    "box_body() invoked on non-box type %s",
+                bcx.tcx().sess.bug(format!(
+                    "box_body() invoked on non-box type {}",
                     ty_to_str(bcx.tcx(), self.ty)));
             }
         };
@@ -620,7 +620,7 @@ impl Datum {
                      -> (Option<Datum>, @mut Block) {
         let ccx = bcx.ccx();
 
-        debug!("try_deref(expr_id=%?, derefs=%?, is_auto=%b, self=%?)",
+        debug2!("try_deref(expr_id={:?}, derefs={:?}, is_auto={}, self={:?})",
                expr_id, derefs, is_auto, self.to_str(bcx.ccx()));
 
         let bcx =
@@ -745,7 +745,7 @@ impl Datum {
                      -> DatumBlock {
         let _icx = push_ctxt("autoderef");
 
-        debug!("autoderef(expr_id=%d, max=%?, self=%?)",
+        debug2!("autoderef(expr_id={}, max={:?}, self={:?})",
                expr_id, max, self.to_str(bcx.ccx()));
         let _indenter = indenter();
 
diff --git a/src/librustc/middle/trans/debuginfo.rs b/src/librustc/middle/trans/debuginfo.rs
index c36d427a06c..3f4c2e8abc5 100644
--- a/src/librustc/middle/trans/debuginfo.rs
+++ b/src/librustc/middle/trans/debuginfo.rs
@@ -142,7 +142,7 @@ pub struct CrateDebugContext {
 
 impl CrateDebugContext {
     pub fn new(llmod: ModuleRef, crate: ~str) -> CrateDebugContext {
-        debug!("CrateDebugContext::new");
+        debug2!("CrateDebugContext::new");
         let builder = unsafe { llvm::LLVMDIBuilderCreate(llmod) };
         // DIBuilder inherits context from the module, so we'd better use the same one
         let llcontext = unsafe { llvm::LLVMGetModuleContext(llmod) };
@@ -240,7 +240,7 @@ pub fn finalize(cx: @mut CrateContext) {
         return;
     }
 
-    debug!("finalize");
+    debug2!("finalize");
     compile_unit_metadata(cx);
     unsafe {
         llvm::LLVMDIBuilderFinalize(DIB(cx));
@@ -268,7 +268,8 @@ pub fn create_local_var_metadata(bcx: @mut Block,
         let llptr = match bcx.fcx.lllocals.find_copy(&node_id) {
             Some(v) => v,
             None => {
-                bcx.tcx().sess.span_bug(span, fmt!("No entry in lllocals table for %?", node_id));
+                bcx.tcx().sess.span_bug(span,
+                    format!("No entry in lllocals table for {:?}", node_id));
             }
         };
 
@@ -310,8 +311,8 @@ pub fn create_captured_var_metadata(bcx: @mut Block,
             ast_util::path_to_ident(path)
         }
         _ => {
-            cx.sess.span_bug(span, fmt!("debuginfo::create_captured_var_metadata() - \
-                Captured var-id refers to unexpected ast_map variant: %?", ast_item));
+            cx.sess.span_bug(span, format!("debuginfo::create_captured_var_metadata() - \
+                Captured var-id refers to unexpected ast_map variant: {:?}", ast_item));
         }
     };
 
@@ -366,7 +367,7 @@ pub fn create_match_binding_metadata(bcx: @mut Block,
     let llptr = match bcx.fcx.lllocals.find_copy(&node_id) {
         Some(v) => v,
         None => {
-            bcx.tcx().sess.span_bug(span, fmt!("No entry in lllocals table for %?", node_id));
+            bcx.tcx().sess.span_bug(span, format!("No entry in lllocals table for {:?}", node_id));
         }
     };
 
@@ -408,7 +409,7 @@ pub fn create_self_argument_metadata(bcx: @mut Block,
             explicit_self.span
         }
         _ => bcx.ccx().sess.bug(
-                fmt!("create_self_argument_metadata: unexpected sort of node: %?", fnitem))
+                format!("create_self_argument_metadata: unexpected sort of node: {:?}", fnitem))
     };
 
     let scope_metadata = bcx.fcx.debug_context.get_ref(bcx.ccx(), span).fn_metadata;
@@ -459,7 +460,8 @@ pub fn create_argument_metadata(bcx: @mut Block,
         let llptr = match bcx.fcx.llargs.find_copy(&node_id) {
             Some(v) => v,
             None => {
-                bcx.tcx().sess.span_bug(span, fmt!("No entry in llargs table for %?", node_id));
+                bcx.tcx().sess.span_bug(span,
+                    format!("No entry in llargs table for {:?}", node_id));
             }
         };
 
@@ -501,7 +503,7 @@ pub fn set_source_location(fcx: &FunctionContext,
 
     let cx = fcx.ccx;
 
-    debug!("set_source_location: %s", cx.sess.codemap.span_to_str(span));
+    debug2!("set_source_location: {}", cx.sess.codemap.span_to_str(span));
 
     if fcx.debug_context.get_ref(cx, span).source_locations_enabled {
         let loc = span_start(cx, span);
@@ -574,7 +576,7 @@ pub fn create_function_debug_context(cx: &mut CrateContext,
         ast_map::node_expr(ref expr) => {
             match expr.node {
                 ast::ExprFnBlock(ref fn_decl, ref top_level_block) => {
-                    let name = fmt!("fn%u", token::gensym("fn"));
+                    let name = format!("fn{}", token::gensym("fn"));
                     let name = token::str_to_ident(name);
                     (name, fn_decl,
                         // This is not quite right. It should actually inherit the generics of the
@@ -606,7 +608,8 @@ pub fn create_function_debug_context(cx: &mut CrateContext,
         ast_map::node_struct_ctor(*) => {
             return FunctionWithoutDebugInfo;
         }
-        _ => cx.sess.bug(fmt!("create_function_debug_context: unexpected sort of node: %?", fnitem))
+        _ => cx.sess.bug(format!("create_function_debug_context: \
+                                  unexpected sort of node: {:?}", fnitem))
     };
 
     // This can be the case for functions inlined from another crate
@@ -637,8 +640,8 @@ pub fn create_function_debug_context(cx: &mut CrateContext,
         }
         None => {
             // This branch is only hit when there is a bug in the NamespaceVisitor.
-            cx.sess.span_warn(span, fmt!("debuginfo: Could not find namespace node for function
-                                          with name %s. This is a bug! Please report this to
+            cx.sess.span_warn(span, format!("debuginfo: Could not find namespace node for function
+                                          with name {}. This is a bug! Please report this to
                                           github.com/mozilla/rust/issues", function_name));
             (function_name.clone(), file_metadata)
         }
@@ -870,10 +873,10 @@ fn compile_unit_metadata(cx: @mut CrateContext) {
     let dcx = debug_context(cx);
     let crate_name: &str = dcx.crate_file;
 
-    debug!("compile_unit_metadata: %?", crate_name);
+    debug2!("compile_unit_metadata: {:?}", crate_name);
 
     let work_dir = cx.sess.working_dir.to_str();
-    let producer = fmt!("rustc version %s", env!("CFG_VERSION"));
+    let producer = format!("rustc version {}", env!("CFG_VERSION"));
 
     do crate_name.with_c_str |crate_name| {
     do work_dir.with_c_str |work_dir| {
@@ -980,7 +983,7 @@ fn file_metadata(cx: &mut CrateContext, full_path: &str) -> DIFile {
         None => ()
     }
 
-    debug!("file_metadata: %s", full_path);
+    debug2!("file_metadata: {}", full_path);
 
     let work_dir = cx.sess.working_dir.to_str();
     let file_name =
@@ -1015,14 +1018,14 @@ fn scope_metadata(fcx: &FunctionContext,
             let node = fcx.ccx.tcx.items.get_copy(&node_id);
 
             fcx.ccx.sess.span_bug(span,
-                fmt!("debuginfo: Could not find scope info for node %?", node));
+                format!("debuginfo: Could not find scope info for node {:?}", node));
         }
     }
 }
 
 fn basic_type_metadata(cx: &mut CrateContext, t: ty::t) -> DIType {
 
-    debug!("basic_type_metadata: %?", ty::get(t));
+    debug2!("basic_type_metadata: {:?}", ty::get(t));
 
     let (name, encoding) = match ty::get(t).sty {
         ty::ty_nil | ty::ty_bot => (~"uint", DW_ATE_unsigned),
@@ -1340,8 +1343,8 @@ fn describe_variant(cx: &mut CrateContext,
             Some(&ast_map::node_variant(ref variant, _, _)) => variant.span,
             ref node => {
                 cx.sess.span_warn(span,
-                    fmt!("debuginfo::enum_metadata()::adt_struct_metadata() - Unexpected node \
-                          type: %?. This is a bug.", node));
+                    format!("debuginfo::enum_metadata()::adt_struct_metadata() - Unexpected node \
+                          type: {:?}. This is a bug.", node));
                 codemap::dummy_sp()
             }
         }
@@ -1659,7 +1662,7 @@ fn boxed_type_metadata(cx: &mut CrateContext,
                        span: Span)
                     -> DICompositeType {
     let box_type_name = match content_type_name {
-        Some(content_type_name) => fmt!("Boxed<%s>", content_type_name),
+        Some(content_type_name) => format!("Boxed<{}>", content_type_name),
         None                    => ~"BoxedType"
     };
 
@@ -1768,7 +1771,7 @@ fn vec_metadata(cx: &mut CrateContext,
     let (element_size, element_align) = size_and_align_of(cx, element_llvm_type);
 
     let vec_llvm_type = Type::vec(cx.sess.targ_cfg.arch, &element_llvm_type);
-    let vec_type_name: &str = fmt!("[%s]", ppaux::ty_to_str(cx.tcx, element_type));
+    let vec_type_name: &str = format!("[{}]", ppaux::ty_to_str(cx.tcx, element_type));
 
     let member_llvm_types = vec_llvm_type.field_types();
 
@@ -1824,7 +1827,7 @@ fn boxed_vec_metadata(cx: &mut CrateContext,
                    -> DICompositeType {
     let element_llvm_type = type_of::type_of(cx, element_type);
     let vec_llvm_type = Type::vec(cx.sess.targ_cfg.arch, &element_llvm_type);
-    let vec_type_name: &str = fmt!("[%s]", ppaux::ty_to_str(cx.tcx, element_type));
+    let vec_type_name: &str = format!("[{}]", ppaux::ty_to_str(cx.tcx, element_type));
     let vec_metadata = vec_metadata(cx, element_type, span);
 
     return boxed_type_metadata(
@@ -1841,7 +1844,7 @@ fn vec_slice_metadata(cx: &mut CrateContext,
                       span: Span)
                    -> DICompositeType {
 
-    debug!("vec_slice_metadata: %?", ty::get(vec_type));
+    debug2!("vec_slice_metadata: {:?}", ty::get(vec_type));
 
     let slice_llvm_type = type_of::type_of(cx, vec_type);
     let slice_type_name = ppaux::ty_to_str(cx.tcx, vec_type);
@@ -1956,10 +1959,10 @@ fn trait_metadata(cx: &mut CrateContext,
 }
 
 fn unimplemented_type_metadata(cx: &mut CrateContext, t: ty::t) -> DIType {
-    debug!("unimplemented_type_metadata: %?", ty::get(t));
+    debug2!("unimplemented_type_metadata: {:?}", ty::get(t));
 
     let name = ppaux::ty_to_str(cx.tcx, t);
-    let metadata = do fmt!("NYI<%s>", name).with_c_str |name| {
+    let metadata = do format!("NYI<{}>", name).with_c_str |name| {
         unsafe {
             llvm::LLVMDIBuilderCreateBasicType(
                 DIB(cx),
@@ -2008,7 +2011,7 @@ fn type_metadata(cx: &mut CrateContext,
         pointer_type_metadata(cx, pointer_type, box_metadata)
     }
 
-    debug!("type_metadata: %?", ty::get(t));
+    debug2!("type_metadata: {:?}", ty::get(t));
 
     let sty = &ty::get(t).sty;
     let type_metadata = match *sty {
@@ -2095,7 +2098,7 @@ fn type_metadata(cx: &mut CrateContext,
         ty::ty_opaque_box => {
             create_pointer_to_box_metadata(cx, t, ty::mk_nil())
         }
-        _ => cx.sess.bug(fmt!("debuginfo: unexpected type in type_metadata: %?", sty))
+        _ => cx.sess.bug(format!("debuginfo: unexpected type in type_metadata: {:?}", sty))
     };
 
     debug_context(cx).created_types.insert(cache_id, type_metadata);
@@ -2127,7 +2130,7 @@ fn set_debug_location(cx: &mut CrateContext, debug_location: DebugLocation) {
 
     match debug_location {
         KnownLocation { scope, line, col } => {
-            debug!("setting debug location to %u %u", line, col);
+            debug2!("setting debug location to {} {}", line, col);
             let elements = [C_i32(line as i32), C_i32(col as i32), scope, ptr::null()];
             unsafe {
                 metadata_node = llvm::LLVMMDNodeInContext(debug_context(cx).llcontext,
@@ -2136,7 +2139,7 @@ fn set_debug_location(cx: &mut CrateContext, debug_location: DebugLocation) {
             }
         }
         UnknownLocation => {
-            debug!("clearing debug location ");
+            debug2!("clearing debug location ");
             metadata_node = ptr::null();
         }
     };
@@ -2202,8 +2205,9 @@ fn get_namespace_and_span_for_item(cx: &mut CrateContext,
         let definition_span = match cx.tcx.items.find(&def_id.node) {
             Some(&ast_map::node_item(@ast::item { span, _ }, _)) => span,
             ref node => {
-                cx.sess.span_warn(warning_span, fmt!("debuginfo::get_namespace_and_span_for_item() \
-                                                      - Unexpected node type: %?", *node));
+                cx.sess.span_warn(warning_span,
+                    format!("debuginfo::get_namespace_and_span_for_item() \
+                             - Unexpected node type: {:?}", *node));
                 codemap::dummy_sp()
             }
         };
@@ -2682,7 +2686,7 @@ impl NamespaceTreeNode {
         let mut name = ~"_ZN";
         fill_nested(self, &mut name);
 
-        name.push_str(fmt!("%u%s", item_name.len(), item_name));
+        name.push_str(format!("{}{}", item_name.len(), item_name));
         name.push_char('E');
 
         return name;
@@ -2695,7 +2699,7 @@ impl NamespaceTreeNode {
                 None => {}
             }
             let name = token::ident_to_str(&node.ident);
-            output.push_str(fmt!("%u%s", name.len(), name));
+            output.push_str(format!("{}{}", name.len(), name));
         }
     }
 }
@@ -2704,7 +2708,7 @@ fn namespace_for_external_item(cx: &mut CrateContext,
                                item_path: &ast_map::path)
                             -> @NamespaceTreeNode {
     if item_path.len() < 2 {
-        cx.sess.bug(fmt!("debuginfo::namespace_for_external_item() - Invalid item_path: %s",
+        cx.sess.bug(format!("debuginfo::namespace_for_external_item() - Invalid item_path: {}",
             ast_map::path_to_str(*item_path, token::get_ident_interner())));
     }
 
diff --git a/src/librustc/middle/trans/expr.rs b/src/librustc/middle/trans/expr.rs
index 56677167f0e..995b2467888 100644
--- a/src/librustc/middle/trans/expr.rs
+++ b/src/librustc/middle/trans/expr.rs
@@ -169,7 +169,7 @@ pub enum Dest {
 impl Dest {
     pub fn to_str(&self, ccx: &CrateContext) -> ~str {
         match *self {
-            SaveIn(v) => fmt!("SaveIn(%s)", ccx.tn.val_to_str(v)),
+            SaveIn(v) => format!("SaveIn({})", ccx.tn.val_to_str(v)),
             Ignore => ~"Ignore"
         }
     }
@@ -182,7 +182,7 @@ fn drop_and_cancel_clean(bcx: @mut Block, dat: Datum) -> @mut Block {
 }
 
 pub fn trans_to_datum(bcx: @mut Block, expr: &ast::Expr) -> DatumBlock {
-    debug!("trans_to_datum(expr=%s)", bcx.expr_to_str(expr));
+    debug2!("trans_to_datum(expr={})", bcx.expr_to_str(expr));
 
     let mut bcx = bcx;
     let mut datum = unpack_datum!(bcx, trans_to_datum_unadjusted(bcx, expr));
@@ -190,7 +190,7 @@ pub fn trans_to_datum(bcx: @mut Block, expr: &ast::Expr) -> DatumBlock {
         None => { return DatumBlock {bcx: bcx, datum: datum}; }
         Some(adj) => { adj }
     };
-    debug!("unadjusted datum: %s", datum.to_str(bcx.ccx()));
+    debug2!("unadjusted datum: {}", datum.to_str(bcx.ccx()));
     match *adjustment {
         AutoAddEnv(*) => {
             datum = unpack_datum!(bcx, add_env(bcx, expr, datum));
@@ -232,7 +232,7 @@ pub fn trans_to_datum(bcx: @mut Block, expr: &ast::Expr) -> DatumBlock {
             };
         }
     }
-    debug!("after adjustments, datum=%s", datum.to_str(bcx.ccx()));
+    debug2!("after adjustments, datum={}", datum.to_str(bcx.ccx()));
     return DatumBlock {bcx: bcx, datum: datum};
 
     fn auto_ref(bcx: @mut Block, datum: Datum) -> DatumBlock {
@@ -287,7 +287,7 @@ pub fn trans_to_datum(bcx: @mut Block, expr: &ast::Expr) -> DatumBlock {
 
         let tcx = bcx.tcx();
         let closure_ty = expr_ty_adjusted(bcx, expr);
-        debug!("add_env(closure_ty=%s)", closure_ty.repr(tcx));
+        debug2!("add_env(closure_ty={})", closure_ty.repr(tcx));
         let scratch = scratch_datum(bcx, closure_ty, "__adjust", false);
         let llfn = GEPi(bcx, scratch.val, [0u, abi::fn_field_code]);
         assert_eq!(datum.appropriate_mode(tcx), ByValue);
@@ -311,7 +311,7 @@ pub fn trans_to_datum(bcx: @mut Block, expr: &ast::Expr) -> DatumBlock {
                        source_datum: Datum) -> DatumBlock {
         let tcx = bcx.tcx();
         let target_obj_ty = expr_ty_adjusted(bcx, expr);
-        debug!("auto_borrow_obj(target=%s)",
+        debug2!("auto_borrow_obj(target={})",
                target_obj_ty.repr(tcx));
 
         // Extract source store information
@@ -320,7 +320,7 @@ pub fn trans_to_datum(bcx: @mut Block, expr: &ast::Expr) -> DatumBlock {
             _ => {
                 bcx.sess().span_bug(
                     expr.span,
-                    fmt!("auto_borrow_trait_obj expected a trait, found %s",
+                    format!("auto_borrow_trait_obj expected a trait, found {}",
                          source_datum.ty.repr(bcx.tcx())));
             }
         };
@@ -432,7 +432,7 @@ pub fn trans_into(bcx: @mut Block, expr: &ast::Expr, dest: Dest) -> @mut Block {
 
     let ty = expr_ty(bcx, expr);
 
-    debug!("trans_into_unadjusted(expr=%s, dest=%s)",
+    debug2!("trans_into_unadjusted(expr={}, dest={})",
            bcx.expr_to_str(expr),
            dest.to_str(bcx.ccx()));
     let _indenter = indenter();
@@ -448,7 +448,7 @@ pub fn trans_into(bcx: @mut Block, expr: &ast::Expr, dest: Dest) -> @mut Block {
     };
 
     let kind = bcx.expr_kind(expr);
-    debug!("expr kind = %?", kind);
+    debug2!("expr kind = {:?}", kind);
     return match kind {
         ty::LvalueExpr => {
             let datumblock = trans_lvalue_unadjusted(bcx, expr);
@@ -490,7 +490,7 @@ fn trans_lvalue(bcx: @mut Block, expr: &ast::Expr) -> DatumBlock {
         Some(_) => {
             bcx.sess().span_bug(
                 expr.span,
-                fmt!("trans_lvalue() called on an expression \
+                format!("trans_lvalue() called on an expression \
                       with adjustments"));
         }
     };
@@ -506,7 +506,7 @@ fn trans_to_datum_unadjusted(bcx: @mut Block, expr: &ast::Expr) -> DatumBlock {
 
     let mut bcx = bcx;
 
-    debug!("trans_to_datum_unadjusted(expr=%s)", bcx.expr_to_str(expr));
+    debug2!("trans_to_datum_unadjusted(expr={})", bcx.expr_to_str(expr));
     let _indenter = indenter();
 
     debuginfo::set_source_location(bcx.fcx, expr.id, expr.span);
@@ -608,8 +608,8 @@ fn trans_rvalue_datum_unadjusted(bcx: @mut Block, expr: &ast::Expr) -> DatumBloc
         _ => {
             bcx.tcx().sess.span_bug(
                 expr.span,
-                fmt!("trans_rvalue_datum_unadjusted reached \
-                      fall-through case: %?",
+                format!("trans_rvalue_datum_unadjusted reached \
+                      fall-through case: {:?}",
                      expr.node));
         }
     }
@@ -662,8 +662,8 @@ fn trans_rvalue_stmt_unadjusted(bcx: @mut Block, expr: &ast::Expr) -> @mut Block
         _ => {
             bcx.tcx().sess.span_bug(
                 expr.span,
-                fmt!("trans_rvalue_stmt_unadjusted reached \
-                      fall-through case: %?",
+                format!("trans_rvalue_stmt_unadjusted reached \
+                      fall-through case: {:?}",
                      expr.node));
         }
     };
@@ -718,7 +718,7 @@ fn trans_rvalue_dps_unadjusted(bcx: @mut Block, expr: &ast::Expr,
         ast::ExprFnBlock(ref decl, ref body) => {
             let expr_ty = expr_ty(bcx, expr);
             let sigil = ty::ty_closure_sigil(expr_ty);
-            debug!("translating fn_block %s with type %s",
+            debug2!("translating fn_block {} with type {}",
                    expr_to_str(expr, tcx.sess.intr()),
                    expr_ty.repr(tcx));
             return closure::trans_expr_fn(bcx, sigil, decl, body,
@@ -787,7 +787,7 @@ fn trans_rvalue_dps_unadjusted(bcx: @mut Block, expr: &ast::Expr,
         _ => {
             bcx.tcx().sess.span_bug(
                 expr.span,
-                fmt!("trans_rvalue_dps_unadjusted reached fall-through case: %?",
+                format!("trans_rvalue_dps_unadjusted reached fall-through case: {:?}",
                      expr.node));
         }
     }
@@ -836,8 +836,8 @@ fn trans_def_dps_unadjusted(bcx: @mut Block, ref_expr: &ast::Expr,
             return bcx;
         }
         _ => {
-            bcx.tcx().sess.span_bug(ref_expr.span, fmt!(
-                "Non-DPS def %? referened by %s",
+            bcx.tcx().sess.span_bug(ref_expr.span, format!(
+                "Non-DPS def {:?} referened by {}",
                 def, bcx.node_id_to_str(ref_expr.id)));
         }
     }
@@ -861,8 +861,8 @@ fn trans_def_datum_unadjusted(bcx: @mut Block,
                                              ref_expr.id)
         }
         _ => {
-            bcx.tcx().sess.span_bug(ref_expr.span, fmt!(
-                "Non-DPS def %? referened by %s",
+            bcx.tcx().sess.span_bug(ref_expr.span, format!(
+                "Non-DPS def {:?} referened by {}",
                 def, bcx.node_id_to_str(ref_expr.id)));
         }
     };
@@ -887,7 +887,7 @@ fn trans_lvalue_unadjusted(bcx: @mut Block, expr: &ast::Expr) -> DatumBlock {
     let _icx = push_ctxt("trans_lval");
     let mut bcx = bcx;
 
-    debug!("trans_lvalue(expr=%s)", bcx.expr_to_str(expr));
+    debug2!("trans_lvalue(expr={})", bcx.expr_to_str(expr));
     let _indenter = indenter();
 
     trace_span!(bcx, expr.span, shorten(bcx.expr_to_str(expr)));
@@ -912,7 +912,7 @@ fn trans_lvalue_unadjusted(bcx: @mut Block, expr: &ast::Expr) -> DatumBlock {
         _ => {
             bcx.tcx().sess.span_bug(
                 expr.span,
-                fmt!("trans_lvalue reached fall-through case: %?",
+                format!("trans_lvalue reached fall-through case: {:?}",
                      expr.node));
         }
     };
@@ -978,8 +978,8 @@ fn trans_lvalue_unadjusted(bcx: @mut Block, expr: &ast::Expr) -> DatumBlock {
             base_datum.get_vec_base_and_len(bcx, index_expr.span,
                                             index_expr.id, 0);
 
-        debug!("trans_index: base %s", bcx.val_to_str(base));
-        debug!("trans_index: len %s", bcx.val_to_str(len));
+        debug2!("trans_index: base {}", bcx.val_to_str(base));
+        debug2!("trans_index: len {}", bcx.val_to_str(len));
 
         let bounds_check = ICmp(bcx, lib::llvm::IntUGE, scaled_ix, len);
         let bcx = do with_cond(bcx, bounds_check) |bcx| {
@@ -1091,8 +1091,8 @@ pub fn trans_local_var(bcx: @mut Block, def: ast::Def) -> Datum {
                     }
                 }
                 None => {
-                    bcx.sess().bug(fmt!(
-                        "trans_local_var: no llval for upvar %? found", nid));
+                    bcx.sess().bug(format!(
+                        "trans_local_var: no llval for upvar {:?} found", nid));
                 }
             }
         }
@@ -1106,13 +1106,13 @@ pub fn trans_local_var(bcx: @mut Block, def: ast::Def) -> Datum {
             let self_info: ValSelfData = match bcx.fcx.llself {
                 Some(ref self_info) => *self_info,
                 None => {
-                    bcx.sess().bug(fmt!(
+                    bcx.sess().bug(format!(
                         "trans_local_var: reference to self \
-                         out of context with id %?", nid));
+                         out of context with id {:?}", nid));
                 }
             };
 
-            debug!("def_self() reference, self_info.t=%s",
+            debug2!("def_self() reference, self_info.t={}",
                    self_info.t.repr(bcx.tcx()));
 
             Datum {
@@ -1122,8 +1122,8 @@ pub fn trans_local_var(bcx: @mut Block, def: ast::Def) -> Datum {
             }
         }
         _ => {
-            bcx.sess().unimpl(fmt!(
-                "unsupported def type in trans_local_var: %?", def));
+            bcx.sess().unimpl(format!(
+                "unsupported def type in trans_local_var: {:?}", def));
         }
     };
 
@@ -1133,12 +1133,12 @@ pub fn trans_local_var(bcx: @mut Block, def: ast::Def) -> Datum {
         let v = match table.find(&nid) {
             Some(&v) => v,
             None => {
-                bcx.sess().bug(fmt!(
-                    "trans_local_var: no llval for local/arg %? found", nid));
+                bcx.sess().bug(format!(
+                    "trans_local_var: no llval for local/arg {:?} found", nid));
             }
         };
         let ty = node_id_type(bcx, nid);
-        debug!("take_local(nid=%?, v=%s, ty=%s)",
+        debug2!("take_local(nid={:?}, v={}, ty={})",
                nid, bcx.val_to_str(v), bcx.ty_to_str(ty));
         Datum {
             val: v,
@@ -1164,8 +1164,8 @@ pub fn with_field_tys<R>(tcx: ty::ctxt,
             // We want the *variant* ID here, not the enum ID.
             match node_id_opt {
                 None => {
-                    tcx.sess.bug(fmt!(
-                        "cannot get field types from the enum type %s \
+                    tcx.sess.bug(format!(
+                        "cannot get field types from the enum type {} \
                          without a node ID",
                         ty.repr(tcx)));
                 }
@@ -1187,8 +1187,8 @@ pub fn with_field_tys<R>(tcx: ty::ctxt,
         }
 
         _ => {
-            tcx.sess.bug(fmt!(
-                "cannot get field types from the type %s",
+            tcx.sess.bug(format!(
+                "cannot get field types from the type {}",
                 ty.repr(tcx)));
         }
     }
@@ -1733,14 +1733,14 @@ fn trans_imm_cast(bcx: @mut Block, expr: &ast::Expr,
                                               val_ty(lldiscrim_a),
                                               lldiscrim_a, true),
                     cast_float => SIToFP(bcx, lldiscrim_a, ll_t_out),
-                    _ => ccx.sess.bug(fmt!("translating unsupported cast: \
-                                           %s (%?) -> %s (%?)",
+                    _ => ccx.sess.bug(format!("translating unsupported cast: \
+                                           {} ({:?}) -> {} ({:?})",
                                            t_in.repr(ccx.tcx), k_in,
                                            t_out.repr(ccx.tcx), k_out))
                 }
             }
-            _ => ccx.sess.bug(fmt!("translating unsupported cast: \
-                                   %s (%?) -> %s (%?)",
+            _ => ccx.sess.bug(format!("translating unsupported cast: \
+                                   {} ({:?}) -> {} ({:?})",
                                    t_in.repr(ccx.tcx), k_in,
                                    t_out.repr(ccx.tcx), k_out))
         };
@@ -1757,7 +1757,7 @@ fn trans_assign_op(bcx: @mut Block,
     let _icx = push_ctxt("trans_assign_op");
     let mut bcx = bcx;
 
-    debug!("trans_assign_op(expr=%s)", bcx.expr_to_str(expr));
+    debug2!("trans_assign_op(expr={})", bcx.expr_to_str(expr));
 
     // Evaluate LHS (destination), which should be an lvalue
     let dst_datum = unpack_datum!(bcx, trans_lvalue_unadjusted(bcx, dst));
diff --git a/src/librustc/middle/trans/foreign.rs b/src/librustc/middle/trans/foreign.rs
index f28f5449e00..6ca0967f8ee 100644
--- a/src/librustc/middle/trans/foreign.rs
+++ b/src/librustc/middle/trans/foreign.rs
@@ -80,13 +80,13 @@ pub fn llvm_calling_convention(ccx: &mut CrateContext,
         match *abi {
             RustIntrinsic => {
                 // Intrinsics are emitted by monomorphic fn
-                ccx.sess.bug(fmt!("Asked to register intrinsic fn"));
+                ccx.sess.bug(format!("Asked to register intrinsic fn"));
             }
 
             Rust => {
                 // FIXME(#3678) Implement linking to foreign fns with Rust ABI
                 ccx.sess.unimpl(
-                    fmt!("Foreign functions with Rust ABI"));
+                    format!("Foreign functions with Rust ABI"));
             }
 
             Stdcall => lib::llvm::X86StdcallCallConv,
@@ -110,9 +110,9 @@ pub fn register_foreign_item_fn(ccx: @mut CrateContext,
      * Just adds a LLVM global.
      */
 
-    debug!("register_foreign_item_fn(abis=%s, \
-            path=%s, \
-            foreign_item.id=%?)",
+    debug2!("register_foreign_item_fn(abis={}, \
+            path={}, \
+            foreign_item.id={:?})",
            abis.repr(ccx.tcx),
            path.repr(ccx.tcx),
            foreign_item.id);
@@ -122,9 +122,9 @@ pub fn register_foreign_item_fn(ccx: @mut CrateContext,
         None => {
             // FIXME(#8357) We really ought to report a span here
             ccx.sess.fatal(
-                fmt!("ABI `%s` has no suitable ABI \
+                format!("ABI `{}` has no suitable ABI \
                       for target architecture \
-                      in module %s",
+                      in module {}",
                      abis.user_string(ccx.tcx),
                      ast_map::path_to_str(*path,
                                           ccx.sess.intr())));
@@ -165,9 +165,9 @@ pub fn trans_native_call(bcx: @mut Block,
     let ccx = bcx.ccx();
     let tcx = bcx.tcx();
 
-    debug!("trans_native_call(callee_ty=%s, \
-            llfn=%s, \
-            llretptr=%s)",
+    debug2!("trans_native_call(callee_ty={}, \
+            llfn={}, \
+            llretptr={})",
            callee_ty.repr(tcx),
            ccx.tn.val_to_str(llfn),
            ccx.tn.val_to_str(llretptr));
@@ -213,7 +213,7 @@ pub fn trans_native_call(bcx: @mut Block,
         // Does Rust pass this argument by pointer?
         let rust_indirect = type_of::arg_is_indirect(ccx, fn_sig.inputs[i]);
 
-        debug!("argument %u, llarg_rust=%s, rust_indirect=%b, arg_ty=%s",
+        debug2!("argument {}, llarg_rust={}, rust_indirect={}, arg_ty={}",
                i,
                ccx.tn.val_to_str(llarg_rust),
                rust_indirect,
@@ -227,7 +227,7 @@ pub fn trans_native_call(bcx: @mut Block,
             llarg_rust = scratch;
         }
 
-        debug!("llarg_rust=%s (after indirection)",
+        debug2!("llarg_rust={} (after indirection)",
                ccx.tn.val_to_str(llarg_rust));
 
         // Check whether we need to do any casting
@@ -236,7 +236,7 @@ pub fn trans_native_call(bcx: @mut Block,
             llarg_rust = BitCast(bcx, llarg_rust, foreignarg_ty.ptr_to());
         }
 
-        debug!("llarg_rust=%s (after casting)",
+        debug2!("llarg_rust={} (after casting)",
                ccx.tn.val_to_str(llarg_rust));
 
         // Finally, load the value if needed for the foreign ABI
@@ -247,7 +247,7 @@ pub fn trans_native_call(bcx: @mut Block,
             Load(bcx, llarg_rust)
         };
 
-        debug!("argument %u, llarg_foreign=%s",
+        debug2!("argument {}, llarg_foreign={}",
                i, ccx.tn.val_to_str(llarg_foreign));
 
         llargs_foreign.push(llarg_foreign);
@@ -258,7 +258,7 @@ pub fn trans_native_call(bcx: @mut Block,
         None => {
             // FIXME(#8357) We really ought to report a span here
             ccx.sess.fatal(
-                fmt!("ABI string `%s` has no suitable ABI \
+                format!("ABI string `{}` has no suitable ABI \
                       for target architecture",
                      fn_abis.user_string(ccx.tcx)));
         }
@@ -284,10 +284,10 @@ pub fn trans_native_call(bcx: @mut Block,
         let llrust_ret_ty = llsig.llret_ty;
         let llforeign_ret_ty = fn_type.ret_ty.ty;
 
-        debug!("llretptr=%s", ccx.tn.val_to_str(llretptr));
-        debug!("llforeign_retval=%s", ccx.tn.val_to_str(llforeign_retval));
-        debug!("llrust_ret_ty=%s", ccx.tn.type_to_str(llrust_ret_ty));
-        debug!("llforeign_ret_ty=%s", ccx.tn.type_to_str(llforeign_ret_ty));
+        debug2!("llretptr={}", ccx.tn.val_to_str(llretptr));
+        debug2!("llforeign_retval={}", ccx.tn.val_to_str(llforeign_retval));
+        debug2!("llrust_ret_ty={}", ccx.tn.type_to_str(llrust_ret_ty));
+        debug2!("llforeign_ret_ty={}", ccx.tn.type_to_str(llforeign_ret_ty));
 
         if llrust_ret_ty == llforeign_ret_ty {
             Store(bcx, llforeign_retval, llretptr);
@@ -313,7 +313,7 @@ pub fn trans_native_call(bcx: @mut Block,
             let llforeign_align = machine::llalign_of_min(ccx, llforeign_ret_ty);
             let llrust_align = machine::llalign_of_min(ccx, llrust_ret_ty);
             let llalign = uint::min(llforeign_align, llrust_align);
-            debug!("llrust_size=%?", llrust_size);
+            debug2!("llrust_size={:?}", llrust_size);
             base::call_memcpy(bcx, llretptr_i8, llscratch_i8,
                               C_uint(ccx, llrust_size), llalign as u32);
         }
@@ -372,7 +372,7 @@ pub fn register_rust_fn_with_foreign_abi(ccx: @mut CrateContext,
                                         lib::llvm::CCallConv,
                                         llfn_ty);
     add_argument_attributes(&tys, llfn);
-    debug!("register_rust_fn_with_foreign_abi(node_id=%?, llfn_ty=%s, llfn=%s)",
+    debug2!("register_rust_fn_with_foreign_abi(node_id={:?}, llfn_ty={}, llfn={})",
            node_id, ccx.tn.type_to_str(llfn_ty), ccx.tn.val_to_str(llfn));
     llfn
 }
@@ -416,14 +416,14 @@ pub fn trans_rust_fn_with_foreign_abi(ccx: @mut CrateContext,
                 f
             }
             _ => {
-                ccx.sess.bug(fmt!("build_rust_fn: extern fn %s has ty %s, \
+                ccx.sess.bug(format!("build_rust_fn: extern fn {} has ty {}, \
                                   expected a bare fn ty",
                                   path.repr(tcx),
                                   t.repr(tcx)));
             }
         };
 
-        debug!("build_rust_fn: path=%s id=%? t=%s",
+        debug2!("build_rust_fn: path={} id={:?} t={}",
                path.repr(tcx),
                id,
                t.repr(tcx));
@@ -449,7 +449,7 @@ pub fn trans_rust_fn_with_foreign_abi(ccx: @mut CrateContext,
             "foreign::trans_rust_fn_with_foreign_abi::build_wrap_fn");
         let tcx = ccx.tcx;
 
-        debug!("build_wrap_fn(llrustfn=%s, llwrapfn=%s)",
+        debug2!("build_wrap_fn(llrustfn={}, llwrapfn={})",
                ccx.tn.val_to_str(llrustfn),
                ccx.tn.val_to_str(llwrapfn));
 
@@ -504,14 +504,14 @@ pub fn trans_rust_fn_with_foreign_abi(ccx: @mut CrateContext,
             // alloca some scratch space on the stack.
             match foreign_outptr {
                 Some(llforeign_outptr) => {
-                    debug!("out pointer, foreign=%s",
+                    debug2!("out pointer, foreign={}",
                            ccx.tn.val_to_str(llforeign_outptr));
                     let llrust_retptr =
                         llvm::LLVMBuildBitCast(builder,
                                                llforeign_outptr,
                                                llrust_ret_ty.ptr_to().to_ref(),
                                                noname());
-                    debug!("out pointer, foreign=%s (casted)",
+                    debug2!("out pointer, foreign={} (casted)",
                            ccx.tn.val_to_str(llrust_retptr));
                     llrust_args.push(llrust_retptr);
                     return_alloca = None;
@@ -524,10 +524,10 @@ pub fn trans_rust_fn_with_foreign_abi(ccx: @mut CrateContext,
                                                       llrust_ret_ty.to_ref(),
                                                       s))
                     };
-                    debug!("out pointer, \
-                            allocad=%s, \
-                            llrust_ret_ty=%s, \
-                            return_ty=%s",
+                    debug2!("out pointer, \
+                            allocad={}, \
+                            llrust_ret_ty={}, \
+                            return_ty={}",
                            ccx.tn.val_to_str(slot),
                            ccx.tn.type_to_str(llrust_ret_ty),
                            tys.fn_sig.output.repr(tcx));
@@ -544,7 +544,7 @@ pub fn trans_rust_fn_with_foreign_abi(ccx: @mut CrateContext,
 
         // Push an (null) env pointer
         let env_pointer = base::null_env_ptr(ccx);
-        debug!("env pointer=%s", ccx.tn.val_to_str(env_pointer));
+        debug2!("env pointer={}", ccx.tn.val_to_str(env_pointer));
         llrust_args.push(env_pointer);
 
         // Build up the arguments to the call to the rust function.
@@ -558,9 +558,9 @@ pub fn trans_rust_fn_with_foreign_abi(ccx: @mut CrateContext,
             let foreign_indirect = tys.fn_ty.attrs[foreign_index].is_some();
             let mut llforeign_arg = llvm::LLVMGetParam(llwrapfn, foreign_index);
 
-            debug!("llforeign_arg #%u: %s",
+            debug2!("llforeign_arg \\#{}: {}",
                    i, ccx.tn.val_to_str(llforeign_arg));
-            debug!("rust_indirect = %b, foreign_indirect = %b",
+            debug2!("rust_indirect = {}, foreign_indirect = {}",
                    rust_indirect, foreign_indirect);
 
             // Ensure that the foreign argument is indirect (by
@@ -591,14 +591,14 @@ pub fn trans_rust_fn_with_foreign_abi(ccx: @mut CrateContext,
                 llvm::LLVMBuildLoad(builder, llforeign_arg, noname())
             };
 
-            debug!("llrust_arg #%u: %s",
+            debug2!("llrust_arg \\#{}: {}",
                    i, ccx.tn.val_to_str(llrust_arg));
             llrust_args.push(llrust_arg);
         }
 
         // Perform the call itself
         let llrust_ret_val = do llrust_args.as_imm_buf |ptr, len| {
-            debug!("calling llrustfn = %s", ccx.tn.val_to_str(llrustfn));
+            debug2!("calling llrustfn = {}", ccx.tn.val_to_str(llrustfn));
             llvm::LLVMBuildCall(builder, llrustfn, ptr,
                                 len as c_uint, noname())
         };
@@ -723,11 +723,11 @@ fn foreign_types_for_fn_ty(ccx: &mut CrateContext,
                                        llsig.llarg_tys,
                                        llsig.llret_ty,
                                        ret_def);
-    debug!("foreign_types_for_fn_ty(\
-           ty=%s, \
-           llsig=%s -> %s, \
-           fn_ty=%s -> %s, \
-           ret_def=%b",
+    debug2!("foreign_types_for_fn_ty(\
+           ty={}, \
+           llsig={} -> {}, \
+           fn_ty={} -> {}, \
+           ret_def={}",
            ty.repr(ccx.tcx),
            ccx.tn.types_to_str(llsig.llarg_tys),
            ccx.tn.type_to_str(llsig.llret_ty),
diff --git a/src/librustc/middle/trans/glue.rs b/src/librustc/middle/trans/glue.rs
index cecea270330..d420514e84f 100644
--- a/src/librustc/middle/trans/glue.rs
+++ b/src/librustc/middle/trans/glue.rs
@@ -213,12 +213,12 @@ pub fn lazily_emit_tydesc_glue(ccx: @mut CrateContext,
         match ti.take_glue {
           Some(_) => (),
           None => {
-            debug!("+++ lazily_emit_tydesc_glue TAKE %s",
+            debug2!("+++ lazily_emit_tydesc_glue TAKE {}",
                    ppaux::ty_to_str(ccx.tcx, ti.ty));
             let glue_fn = declare_generic_glue(ccx, ti.ty, llfnty, "take");
             ti.take_glue = Some(glue_fn);
             make_generic_glue(ccx, ti.ty, glue_fn, make_take_glue, "take");
-            debug!("--- lazily_emit_tydesc_glue TAKE %s",
+            debug2!("--- lazily_emit_tydesc_glue TAKE {}",
                    ppaux::ty_to_str(ccx.tcx, ti.ty));
           }
         }
@@ -226,12 +226,12 @@ pub fn lazily_emit_tydesc_glue(ccx: @mut CrateContext,
         match ti.drop_glue {
           Some(_) => (),
           None => {
-            debug!("+++ lazily_emit_tydesc_glue DROP %s",
+            debug2!("+++ lazily_emit_tydesc_glue DROP {}",
                    ppaux::ty_to_str(ccx.tcx, ti.ty));
             let glue_fn = declare_generic_glue(ccx, ti.ty, llfnty, "drop");
             ti.drop_glue = Some(glue_fn);
             make_generic_glue(ccx, ti.ty, glue_fn, make_drop_glue, "drop");
-            debug!("--- lazily_emit_tydesc_glue DROP %s",
+            debug2!("--- lazily_emit_tydesc_glue DROP {}",
                    ppaux::ty_to_str(ccx.tcx, ti.ty));
           }
         }
@@ -239,12 +239,12 @@ pub fn lazily_emit_tydesc_glue(ccx: @mut CrateContext,
         match ti.free_glue {
           Some(_) => (),
           None => {
-            debug!("+++ lazily_emit_tydesc_glue FREE %s",
+            debug2!("+++ lazily_emit_tydesc_glue FREE {}",
                    ppaux::ty_to_str(ccx.tcx, ti.ty));
             let glue_fn = declare_generic_glue(ccx, ti.ty, llfnty, "free");
             ti.free_glue = Some(glue_fn);
             make_generic_glue(ccx, ti.ty, glue_fn, make_free_glue, "free");
-            debug!("--- lazily_emit_tydesc_glue FREE %s",
+            debug2!("--- lazily_emit_tydesc_glue FREE {}",
                    ppaux::ty_to_str(ccx.tcx, ti.ty));
           }
         }
@@ -252,12 +252,12 @@ pub fn lazily_emit_tydesc_glue(ccx: @mut CrateContext,
         match ti.visit_glue {
           Some(_) => (),
           None => {
-            debug!("+++ lazily_emit_tydesc_glue VISIT %s",
+            debug2!("+++ lazily_emit_tydesc_glue VISIT {}",
                    ppaux::ty_to_str(ccx.tcx, ti.ty));
             let glue_fn = declare_generic_glue(ccx, ti.ty, llfnty, "visit");
             ti.visit_glue = Some(glue_fn);
             make_generic_glue(ccx, ti.ty, glue_fn, make_visit_glue, "visit");
-            debug!("--- lazily_emit_tydesc_glue VISIT %s",
+            debug2!("--- lazily_emit_tydesc_glue VISIT {}",
                    ppaux::ty_to_str(ccx.tcx, ti.ty));
           }
         }
@@ -658,7 +658,7 @@ pub fn declare_tydesc(ccx: &mut CrateContext, t: ty::t) -> @mut tydesc_info {
     let llalign = llalign_of(ccx, llty);
     let name = mangle_internal_name_by_type_and_seq(ccx, t, "tydesc").to_managed();
     note_unique_llvm_symbol(ccx, name);
-    debug!("+++ declare_tydesc %s %s", ppaux::ty_to_str(ccx.tcx, t), name);
+    debug2!("+++ declare_tydesc {} {}", ppaux::ty_to_str(ccx.tcx, t), name);
     let gvar = do name.with_c_str |buf| {
         unsafe {
             llvm::LLVMAddGlobal(ccx.llmod, ccx.tydesc_type.to_ref(), buf)
@@ -679,7 +679,7 @@ pub fn declare_tydesc(ccx: &mut CrateContext, t: ty::t) -> @mut tydesc_info {
         free_glue: None,
         visit_glue: None
     };
-    debug!("--- declare_tydesc %s", ppaux::ty_to_str(ccx.tcx, t));
+    debug2!("--- declare_tydesc {}", ppaux::ty_to_str(ccx.tcx, t));
     return inf;
 }
 
@@ -689,7 +689,7 @@ pub fn declare_generic_glue(ccx: &mut CrateContext, t: ty::t, llfnty: Type,
                             name: &str) -> ValueRef {
     let _icx = push_ctxt("declare_generic_glue");
     let fn_nm = mangle_internal_name_by_type_and_seq(ccx, t, (~"glue_" + name)).to_managed();
-    debug!("%s is for type %s", fn_nm, ppaux::ty_to_str(ccx.tcx, t));
+    debug2!("{} is for type {}", fn_nm, ppaux::ty_to_str(ccx.tcx, t));
     note_unique_llvm_symbol(ccx, fn_nm);
     let llfn = decl_cdecl_fn(ccx.llmod, fn_nm, llfnty);
     set_glue_inlining(llfn, t);
@@ -730,7 +730,7 @@ pub fn make_generic_glue(ccx: @mut CrateContext,
                          name: &str)
                       -> ValueRef {
     let _icx = push_ctxt("make_generic_glue");
-    let glue_name = fmt!("glue %s %s", name, ty_to_short_str(ccx.tcx, t));
+    let glue_name = format!("glue {} {}", name, ty_to_short_str(ccx.tcx, t));
     let _s = StatRecorder::new(ccx, glue_name);
     make_generic_glue_inner(ccx, t, llfn, helper)
 }
@@ -789,8 +789,7 @@ pub fn emit_tydescs(ccx: &mut CrateContext) {
               }
             };
 
-        debug!("ti.borrow_offset: %s",
-               ccx.tn.val_to_str(ti.borrow_offset));
+        debug2!("ti.borrow_offset: {}", ccx.tn.val_to_str(ti.borrow_offset));
 
         let tydesc = C_named_struct(ccx.tydesc_type,
                                     [ti.size, // size
diff --git a/src/librustc/middle/trans/inline.rs b/src/librustc/middle/trans/inline.rs
index 8900b50b49d..de117a7c037 100644
--- a/src/librustc/middle/trans/inline.rs
+++ b/src/librustc/middle/trans/inline.rs
@@ -29,7 +29,7 @@ pub fn maybe_instantiate_inline(ccx: @mut CrateContext, fn_id: ast::DefId)
     match ccx.external.find(&fn_id) {
         Some(&Some(node_id)) => {
             // Already inline
-            debug!("maybe_instantiate_inline(%s): already inline as node id %d",
+            debug2!("maybe_instantiate_inline({}): already inline as node id {}",
                    ty::item_path_str(ccx.tcx, fn_id), node_id);
             return local_def(node_id);
         }
@@ -132,7 +132,7 @@ pub fn maybe_instantiate_inline(ccx: @mut CrateContext, fn_id: ast::DefId)
                   _ => {
                       let self_ty = ty::node_id_to_type(ccx.tcx,
                                                         mth.self_id);
-                      debug!("calling inline trans_fn with self_ty %s",
+                      debug2!("calling inline trans_fn with self_ty {}",
                              ty_to_str(ccx.tcx, self_ty));
                       match mth.explicit_self.node {
                           ast::sty_value => impl_self(self_ty, ty::ByRef),
diff --git a/src/librustc/middle/trans/intrinsic.rs b/src/librustc/middle/trans/intrinsic.rs
index 7933e97a602..da71e99badb 100644
--- a/src/librustc/middle/trans/intrinsic.rs
+++ b/src/librustc/middle/trans/intrinsic.rs
@@ -39,7 +39,7 @@ pub fn trans_intrinsic(ccx: @mut CrateContext,
                        substs: @param_substs,
                        attributes: &[ast::Attribute],
                        ref_id: Option<ast::NodeId>) {
-    debug!("trans_intrinsic(item.ident=%s)", ccx.sess.str_of(item.ident));
+    debug2!("trans_intrinsic(item.ident={})", ccx.sess.str_of(item.ident));
 
     fn simple_llvm_intrinsic(bcx: @mut Block, name: &'static str, num_args: uint) {
         assert!(num_args <= 4);
@@ -299,13 +299,13 @@ pub fn trans_intrinsic(ccx: @mut CrateContext,
             if in_type_size != out_type_size {
                 let sp = match ccx.tcx.items.get_copy(&ref_id.unwrap()) {
                     ast_map::node_expr(e) => e.span,
-                    _ => fail!("transmute has non-expr arg"),
+                    _ => fail2!("transmute has non-expr arg"),
                 };
                 let pluralize = |n| if 1u == n { "" } else { "s" };
                 ccx.sess.span_fatal(sp,
-                                    fmt!("transmute called on types with \
-                                          different sizes: %s (%u bit%s) to \
-                                          %s (%u bit%s)",
+                                    format!("transmute called on types with \
+                                          different sizes: {} ({} bit{}) to \
+                                          {} ({} bit{})",
                                          ty_to_str(ccx.tcx, in_type),
                                          in_type_size,
                                          pluralize(in_type_size),
diff --git a/src/librustc/middle/trans/llrepr.rs b/src/librustc/middle/trans/llrepr.rs
index 43fd6625766..ffb70abcec5 100644
--- a/src/librustc/middle/trans/llrepr.rs
+++ b/src/librustc/middle/trans/llrepr.rs
@@ -19,7 +19,7 @@ pub trait LlvmRepr {
 impl<'self, T:LlvmRepr> LlvmRepr for &'self [T] {
     fn llrepr(&self, ccx: &CrateContext) -> ~str {
         let reprs = self.map(|t| t.llrepr(ccx));
-        fmt!("[%s]", reprs.connect(","))
+        format!("[{}]", reprs.connect(","))
     }
 }
 
diff --git a/src/librustc/middle/trans/meth.rs b/src/librustc/middle/trans/meth.rs
index 19e2e1d00f6..03eb4f18784 100644
--- a/src/librustc/middle/trans/meth.rs
+++ b/src/librustc/middle/trans/meth.rs
@@ -55,7 +55,7 @@ pub fn trans_impl(ccx: @mut CrateContext,
     let _icx = push_ctxt("impl::trans_impl");
     let tcx = ccx.tcx;
 
-    debug!("trans_impl(path=%s, name=%s, id=%?)",
+    debug2!("trans_impl(path={}, name={}, id={:?})",
            path.repr(tcx), name.repr(tcx), id);
 
     // Both here and below with generic methods, be sure to recurse and look for
@@ -117,7 +117,7 @@ pub fn trans_method(ccx: @mut CrateContext,
                 ty::subst_tps(ccx.tcx, *tys, *self_sub, self_ty)
             }
         };
-        debug!("calling trans_fn with self_ty %s",
+        debug2!("calling trans_fn with self_ty {}",
                self_ty.repr(ccx.tcx));
         match method.explicit_self.node {
           ast::sty_value => impl_self(self_ty, ty::ByRef),
@@ -161,7 +161,7 @@ pub fn trans_method_callee(bcx: @mut Block,
                            -> Callee {
     let _icx = push_ctxt("impl::trans_method_callee");
 
-    debug!("trans_method_callee(callee_id=%?, this=%s, mentry=%s)",
+    debug2!("trans_method_callee(callee_id={:?}, this={}, mentry={})",
            callee_id,
            bcx.expr_to_str(this),
            mentry.repr(bcx.tcx()));
@@ -199,7 +199,7 @@ pub fn trans_method_callee(bcx: @mut Block,
                                                trait_id, off, vtbl)
                 }
                 // how to get rid of this?
-                None => fail!("trans_method_callee: missing param_substs")
+                None => fail2!("trans_method_callee: missing param_substs")
             }
         }
 
@@ -220,8 +220,8 @@ pub fn trans_static_method_callee(bcx: @mut Block,
     let _icx = push_ctxt("impl::trans_static_method_callee");
     let ccx = bcx.ccx();
 
-    debug!("trans_static_method_callee(method_id=%?, trait_id=%s, \
-            callee_id=%?)",
+    debug2!("trans_static_method_callee(method_id={:?}, trait_id={}, \
+            callee_id={:?})",
            method_id,
            ty::item_path_str(bcx.tcx(), trait_id),
            callee_id);
@@ -250,17 +250,17 @@ pub fn trans_static_method_callee(bcx: @mut Block,
             ast_map::node_trait_method(trait_method, _, _) => {
                 ast_util::trait_method_to_ty_method(trait_method).ident
             }
-            _ => fail!("callee is not a trait method")
+            _ => fail2!("callee is not a trait method")
         }
     } else {
         let path = csearch::get_item_path(bcx.tcx(), method_id);
         match path[path.len()-1] {
             path_pretty_name(s, _) | path_name(s) => { s }
-            path_mod(_) => { fail!("path doesn't have a name?") }
+            path_mod(_) => { fail2!("path doesn't have a name?") }
         }
     };
-    debug!("trans_static_method_callee: method_id=%?, callee_id=%?, \
-            name=%s", method_id, callee_id, ccx.sess.str_of(mname));
+    debug2!("trans_static_method_callee: method_id={:?}, callee_id={:?}, \
+            name={}", method_id, callee_id, ccx.sess.str_of(mname));
 
     let vtbls = resolve_vtables_in_fn_ctxt(
         bcx.fcx, ccx.maps.vtable_map.get_copy(&callee_id));
@@ -287,7 +287,7 @@ pub fn trans_static_method_callee(bcx: @mut Block,
             FnData {llfn: PointerCast(bcx, lval, llty)}
         }
         _ => {
-            fail!("vtable_param left in monomorphized \
+            fail2!("vtable_param left in monomorphized \
                    function's vtable substs");
         }
     }
@@ -362,7 +362,7 @@ pub fn trans_monomorphized_callee(bcx: @mut Block,
           }
       }
       typeck::vtable_param(*) => {
-          fail!("vtable_param left in monomorphized function's vtable substs");
+          fail2!("vtable_param left in monomorphized function's vtable substs");
       }
     };
 
@@ -395,13 +395,13 @@ pub fn combine_impl_and_methods_tps(bcx: @mut Block,
     let method = ty::method(ccx.tcx, mth_did);
     let n_m_tps = method.generics.type_param_defs.len();
     let node_substs = node_id_type_params(bcx, callee_id);
-    debug!("rcvr_substs=%?", rcvr_substs.repr(ccx.tcx));
+    debug2!("rcvr_substs={:?}", rcvr_substs.repr(ccx.tcx));
     let ty_substs
         = vec::append(rcvr_substs.to_owned(),
                       node_substs.tailn(node_substs.len() - n_m_tps));
-    debug!("n_m_tps=%?", n_m_tps);
-    debug!("node_substs=%?", node_substs.repr(ccx.tcx));
-    debug!("ty_substs=%?", ty_substs.repr(ccx.tcx));
+    debug2!("n_m_tps={:?}", n_m_tps);
+    debug2!("node_substs={:?}", node_substs.repr(ccx.tcx));
+    debug2!("ty_substs={:?}", ty_substs.repr(ccx.tcx));
 
 
     // Now, do the same work for the vtables.  The vtables might not
@@ -474,13 +474,13 @@ pub fn trans_trait_callee_from_llval(bcx: @mut Block,
     let ccx = bcx.ccx();
 
     // Load the data pointer from the object.
-    debug!("(translating trait callee) loading second index from pair");
+    debug2!("(translating trait callee) loading second index from pair");
     let llboxptr = GEPi(bcx, llpair, [0u, abi::trt_field_box]);
     let llbox = Load(bcx, llboxptr);
     let llself = PointerCast(bcx, llbox, Type::opaque_box(ccx).ptr_to());
 
     // Load the function from the vtable and cast it to the expected type.
-    debug!("(translating trait callee) loading method");
+    debug2!("(translating trait callee) loading method");
     let llcallee_ty = type_of_fn_from_ty(ccx, callee_ty);
     let llvtable = Load(bcx,
                         PointerCast(bcx,
@@ -524,7 +524,7 @@ pub fn vtable_id(ccx: @mut CrateContext,
         }
 
         // can't this be checked at the callee?
-        _ => fail!("vtable_id")
+        _ => fail2!("vtable_id")
     }
 }
 
@@ -578,7 +578,7 @@ pub fn make_vtable(ccx: &mut CrateContext,
 
         let tbl = C_struct(components);
         let sym = token::gensym("vtable");
-        let vt_gvar = do fmt!("vtable%u", sym).with_c_str |buf| {
+        let vt_gvar = do format!("vtable{}", sym).with_c_str |buf| {
             llvm::LLVMAddGlobal(ccx.llmod, val_ty(tbl).to_ref(), buf)
         };
         llvm::LLVMSetInitializer(vt_gvar, tbl);
@@ -611,7 +611,7 @@ fn emit_vtable_methods(bcx: @mut Block,
         // the method type from the impl to substitute into.
         let m_id = method_with_name(ccx, impl_id, ident.name);
         let m = ty::method(tcx, m_id);
-        debug!("(making impl vtable) emitting method %s at subst %s",
+        debug2!("(making impl vtable) emitting method {} at subst {}",
                m.repr(tcx),
                substs.repr(tcx));
         let fty = ty::subst_tps(tcx,
@@ -619,7 +619,7 @@ fn emit_vtable_methods(bcx: @mut Block,
                                 None,
                                 ty::mk_bare_fn(tcx, m.fty.clone()));
         if m.generics.has_type_params() || ty::type_has_self(fty) {
-            debug!("(making impl vtable) method has self or type params: %s",
+            debug2!("(making impl vtable) method has self or type params: {}",
                    tcx.sess.str_of(ident));
             C_null(Type::nil().ptr_to())
         } else {
diff --git a/src/librustc/middle/trans/monomorphize.rs b/src/librustc/middle/trans/monomorphize.rs
index 034320008cd..79b3453037d 100644
--- a/src/librustc/middle/trans/monomorphize.rs
+++ b/src/librustc/middle/trans/monomorphize.rs
@@ -36,12 +36,12 @@ pub fn monomorphic_fn(ccx: @mut CrateContext,
                       ref_id: Option<ast::NodeId>)
     -> (ValueRef, bool)
 {
-    debug!("monomorphic_fn(\
-            fn_id=%s, \
-            real_substs=%s, \
-            vtables=%s, \
-            self_vtable=%s, \
-            ref_id=%?)",
+    debug2!("monomorphic_fn(\
+            fn_id={}, \
+            real_substs={}, \
+            vtables={}, \
+            self_vtable={}, \
+            ref_id={:?})",
            fn_id.repr(ccx.tcx),
            real_substs.repr(ccx.tcx),
            vtables.repr(ccx.tcx),
@@ -68,17 +68,17 @@ pub fn monomorphic_fn(ccx: @mut CrateContext,
         must_cast = true;
     }
 
-    debug!("monomorphic_fn(\
-            fn_id=%s, \
-            psubsts=%s, \
-            hash_id=%?)",
+    debug2!("monomorphic_fn(\
+            fn_id={}, \
+            psubsts={}, \
+            hash_id={:?})",
            fn_id.repr(ccx.tcx),
            psubsts.repr(ccx.tcx),
            hash_id);
 
     match ccx.monomorphized.find(&hash_id) {
       Some(&val) => {
-        debug!("leaving monomorphic fn %s",
+        debug2!("leaving monomorphic fn {}",
                ty::item_path_str(ccx.tcx, fn_id));
         return (val, must_cast);
       }
@@ -95,7 +95,7 @@ pub fn monomorphic_fn(ccx: @mut CrateContext,
     let map_node = session::expect(
         ccx.sess,
         ccx.tcx.items.find_copy(&fn_id.node),
-        || fmt!("While monomorphizing %?, couldn't find it in the item map \
+        || format!("While monomorphizing {:?}, couldn't find it in the item map \
                  (may have attempted to monomorphize an item \
                  defined in a different crate?)", fn_id));
     // Get the path so that we can create a symbol
@@ -140,7 +140,7 @@ pub fn monomorphic_fn(ccx: @mut CrateContext,
       ast_map::node_struct_ctor(_, i, pt) => (pt, i.ident, i.span)
     };
 
-    debug!("monomorphic_fn about to subst into %s", llitem_ty.repr(ccx.tcx));
+    debug2!("monomorphic_fn about to subst into {}", llitem_ty.repr(ccx.tcx));
     let mono_ty = match is_static_provided {
         None => ty::subst_tps(ccx.tcx, psubsts.tys,
                               psubsts.self_ty, llitem_ty),
@@ -164,7 +164,7 @@ pub fn monomorphic_fn(ccx: @mut CrateContext,
                 (psubsts.tys.slice(0, idx) +
                  &[psubsts.self_ty.unwrap()] +
                  psubsts.tys.tailn(idx));
-            debug!("static default: changed substitution to %s",
+            debug2!("static default: changed substitution to {}",
                    substs.repr(ccx.tcx));
 
             ty::subst_tps(ccx.tcx, substs, None, llitem_ty)
@@ -176,7 +176,7 @@ pub fn monomorphic_fn(ccx: @mut CrateContext,
             assert!(f.abis.is_rust() || f.abis.is_intrinsic());
             f
         }
-        _ => fail!("expected bare rust fn or an intrinsic")
+        _ => fail2!("expected bare rust fn or an intrinsic")
     };
 
     ccx.stats.n_monos += 1;
@@ -197,7 +197,7 @@ pub fn monomorphic_fn(ccx: @mut CrateContext,
     let mut pt = (*pt).clone();
     pt.push(elt);
     let s = mangle_exported_name(ccx, pt.clone(), mono_ty);
-    debug!("monomorphize_fn mangled to %s", s);
+    debug2!("monomorphize_fn mangled to {}", s);
 
     let mk_lldecl = || {
         let lldecl = decl_internal_rust_fn(ccx, f.sig.inputs, f.sig.output, s);
@@ -285,12 +285,12 @@ pub fn monomorphic_fn(ccx: @mut CrateContext,
       ast_map::node_block(*) |
       ast_map::node_callee_scope(*) |
       ast_map::node_local(*) => {
-        ccx.tcx.sess.bug(fmt!("Can't monomorphize a %?", map_node))
+        ccx.tcx.sess.bug(format!("Can't monomorphize a {:?}", map_node))
       }
     };
     ccx.monomorphizing.insert(fn_id, depth);
 
-    debug!("leaving monomorphic fn %s", ty::item_path_str(ccx.tcx, fn_id));
+    debug2!("leaving monomorphic fn {}", ty::item_path_str(ccx.tcx, fn_id));
     (lldecl, must_cast)
 }
 
@@ -302,7 +302,7 @@ pub fn make_mono_id(ccx: @mut CrateContext,
     let substs_iter = substs.self_ty.iter().chain(substs.tys.iter());
     let precise_param_ids: ~[(ty::t, Option<@~[mono_id]>)] = match substs.vtables {
       Some(vts) => {
-        debug!("make_mono_id vtables=%s substs=%s",
+        debug2!("make_mono_id vtables={} substs={}",
                vts.repr(ccx.tcx), substs.tys.repr(ccx.tcx));
         let vts_iter = substs.self_vtables.iter().chain(vts.iter());
         vts_iter.zip(substs_iter).map(|(vtable, subst)| {
diff --git a/src/librustc/middle/trans/reflect.rs b/src/librustc/middle/trans/reflect.rs
index 23b87c63d6a..b63533b1559 100644
--- a/src/librustc/middle/trans/reflect.rs
+++ b/src/librustc/middle/trans/reflect.rs
@@ -93,15 +93,15 @@ impl Reflector {
         let tcx = self.bcx.tcx();
         let mth_idx = ty::method_idx(
             tcx.sess.ident_of(~"visit_" + ty_name),
-            *self.visitor_methods).expect(fmt!("Couldn't find visit method \
-                                                for %s", ty_name));
+            *self.visitor_methods).expect(format!("Couldn't find visit method \
+                                                for {}", ty_name));
         let mth_ty =
             ty::mk_bare_fn(tcx, self.visitor_methods[mth_idx].fty.clone());
         let v = self.visitor_val;
-        debug!("passing %u args:", args.len());
+        debug2!("passing {} args:", args.len());
         let mut bcx = self.bcx;
         for (i, a) in args.iter().enumerate() {
-            debug!("arg %u: %s", i, bcx.val_to_str(*a));
+            debug2!("arg {}: {}", i, bcx.val_to_str(*a));
         }
         let bool_ty = ty::mk_bool();
         let result = unpack_result!(bcx, callee::trans_call_inner(
@@ -151,7 +151,7 @@ impl Reflector {
     pub fn visit_ty(&mut self, t: ty::t) {
         let bcx = self.bcx;
         let tcx = bcx.ccx().tcx;
-        debug!("reflect::visit_ty %s", ty_to_str(bcx.ccx().tcx, t));
+        debug2!("reflect::visit_ty {}", ty_to_str(bcx.ccx().tcx, t));
 
         match ty::get(t).sty {
           ty::ty_bot => self.leaf("bot"),
diff --git a/src/librustc/middle/trans/tvec.rs b/src/librustc/middle/trans/tvec.rs
index 6a9b2217266..896ce4be337 100644
--- a/src/librustc/middle/trans/tvec.rs
+++ b/src/librustc/middle/trans/tvec.rs
@@ -149,7 +149,7 @@ pub struct VecTypes {
 
 impl VecTypes {
     pub fn to_str(&self, ccx: &CrateContext) -> ~str {
-        fmt!("VecTypes {vec_ty=%s, unit_ty=%s, llunit_ty=%s, llunit_size=%s}",
+        format!("VecTypes \\{vec_ty={}, unit_ty={}, llunit_ty={}, llunit_size={}\\}",
              ty_to_str(ccx.tcx, self.vec_ty),
              ty_to_str(ccx.tcx, self.unit_ty),
              ccx.tn.type_to_str(self.llunit_ty),
@@ -169,7 +169,7 @@ pub fn trans_fixed_vstore(bcx: @mut Block,
     // to store the array of the suitable size, so all we have to do is
     // generate the content.
 
-    debug!("trans_fixed_vstore(vstore_expr=%s, dest=%?)",
+    debug2!("trans_fixed_vstore(vstore_expr={}, dest={:?})",
            bcx.expr_to_str(vstore_expr), dest.to_str(bcx.ccx()));
     let _indenter = indenter();
 
@@ -199,7 +199,7 @@ pub fn trans_slice_vstore(bcx: @mut Block,
 
     let ccx = bcx.ccx();
 
-    debug!("trans_slice_vstore(vstore_expr=%s, dest=%s)",
+    debug2!("trans_slice_vstore(vstore_expr={}, dest={})",
            bcx.expr_to_str(vstore_expr), dest.to_str(ccx));
     let _indenter = indenter();
 
@@ -214,7 +214,7 @@ pub fn trans_slice_vstore(bcx: @mut Block,
     // Handle the &[...] case:
     let vt = vec_types_from_expr(bcx, vstore_expr);
     let count = elements_required(bcx, content_expr);
-    debug!("vt=%s, count=%?", vt.to_str(ccx), count);
+    debug2!("vt={}, count={:?}", vt.to_str(ccx), count);
 
     // Make a fixed-length backing array and allocate it on the stack.
     let llcount = C_uint(ccx, count);
@@ -256,7 +256,7 @@ pub fn trans_lit_str(bcx: @mut Block,
     // different from trans_slice_vstore() above because it does need to copy
     // the content anywhere.
 
-    debug!("trans_lit_str(lit_expr=%s, dest=%s)",
+    debug2!("trans_lit_str(lit_expr={}, dest={})",
            bcx.expr_to_str(lit_expr),
            dest.to_str(bcx.ccx()));
     let _indenter = indenter();
@@ -287,7 +287,7 @@ pub fn trans_uniq_or_managed_vstore(bcx: @mut Block, heap: heap, vstore_expr: &a
     // @[...] or ~[...] (also @"..." or ~"...") allocate boxes in the
     // appropriate heap and write the array elements into them.
 
-    debug!("trans_uniq_or_managed_vstore(vstore_expr=%s, heap=%?)",
+    debug2!("trans_uniq_or_managed_vstore(vstore_expr={}, heap={:?})",
            bcx.expr_to_str(vstore_expr), heap);
     let _indenter = indenter();
 
@@ -318,7 +318,7 @@ pub fn trans_uniq_or_managed_vstore(bcx: @mut Block, heap: heap, vstore_expr: &a
                 _ => {}
             }
         }
-        heap_exchange_closure => fail!("vectors use exchange_alloc"),
+        heap_exchange_closure => fail2!("vectors use exchange_alloc"),
         heap_managed | heap_managed_unique => {}
     }
 
@@ -330,7 +330,7 @@ pub fn trans_uniq_or_managed_vstore(bcx: @mut Block, heap: heap, vstore_expr: &a
     add_clean_free(bcx, val, heap);
     let dataptr = get_dataptr(bcx, get_bodyptr(bcx, val, vt.vec_ty));
 
-    debug!("alloc_vec() returned val=%s, dataptr=%s",
+    debug2!("alloc_vec() returned val={}, dataptr={}",
            bcx.val_to_str(val), bcx.val_to_str(dataptr));
 
     let bcx = write_content(bcx, &vt, vstore_expr,
@@ -350,7 +350,7 @@ pub fn write_content(bcx: @mut Block,
     let _icx = push_ctxt("tvec::write_content");
     let mut bcx = bcx;
 
-    debug!("write_content(vt=%s, dest=%s, vstore_expr=%?)",
+    debug2!("write_content(vt={}, dest={}, vstore_expr={:?})",
            vt.to_str(bcx.ccx()),
            dest.to_str(bcx.ccx()),
            bcx.expr_to_str(vstore_expr));
@@ -383,7 +383,7 @@ pub fn write_content(bcx: @mut Block,
                     let mut temp_cleanups = ~[];
                     for (i, element) in elements.iter().enumerate() {
                         let lleltptr = GEPi(bcx, lldest, [i]);
-                        debug!("writing index %? with lleltptr=%?",
+                        debug2!("writing index {:?} with lleltptr={:?}",
                                i, bcx.val_to_str(lleltptr));
                         bcx = expr::trans_into(bcx, *element,
                                                SaveIn(lleltptr));
diff --git a/src/librustc/middle/trans/type_.rs b/src/librustc/middle/trans/type_.rs
index 0954302ba81..4a7351c207d 100644
--- a/src/librustc/middle/trans/type_.rs
+++ b/src/librustc/middle/trans/type_.rs
@@ -364,7 +364,7 @@ impl Type {
             Double => 64,
             X86_FP80 => 80,
             FP128 | PPC_FP128 => 128,
-            _ => fail!("llvm_float_width called on a non-float type")
+            _ => fail2!("llvm_float_width called on a non-float type")
         }
     }
 }
diff --git a/src/librustc/middle/trans/type_of.rs b/src/librustc/middle/trans/type_of.rs
index aab24f8365b..72b7281148c 100644
--- a/src/librustc/middle/trans/type_of.rs
+++ b/src/librustc/middle/trans/type_of.rs
@@ -162,7 +162,7 @@ pub fn sizing_type_of(cx: &mut CrateContext, t: ty::t) -> Type {
         }
 
         ty::ty_self(_) | ty::ty_infer(*) | ty::ty_param(*) | ty::ty_err(*) => {
-            cx.tcx.sess.bug(fmt!("fictitious type %? in sizing_type_of()", ty::get(t).sty))
+            cx.tcx.sess.bug(format!("fictitious type {:?} in sizing_type_of()", ty::get(t).sty))
         }
     };
 
@@ -172,7 +172,7 @@ pub fn sizing_type_of(cx: &mut CrateContext, t: ty::t) -> Type {
 
 // NB: If you update this, be sure to update `sizing_type_of()` as well.
 pub fn type_of(cx: &mut CrateContext, t: ty::t) -> Type {
-    debug!("type_of %?: %?", t, ty::get(t));
+    debug2!("type_of {:?}: {:?}", t, ty::get(t));
 
     // Check the cache.
     match cx.lltypes.find(&t) {
@@ -335,9 +335,9 @@ pub fn llvm_type_name(cx: &CrateContext,
     let tstr = ppaux::parameterized(cx.tcx, ty::item_path_str(cx.tcx, did),
                                     &ty::NonerasedRegions(opt_vec::Empty), tps);
     if did.crate == 0 {
-        fmt!("%s.%s", name, tstr)
+        format!("{}.{}", name, tstr)
     } else {
-        fmt!("%s.%s[#%d]", name, tstr, did.crate)
+        format!("{}.{}[\\#{}]", name, tstr, did.crate)
     }
 }
 
diff --git a/src/librustc/middle/trans/write_guard.rs b/src/librustc/middle/trans/write_guard.rs
index ad999e0c1aa..f6c1741a9bd 100644
--- a/src/librustc/middle/trans/write_guard.rs
+++ b/src/librustc/middle/trans/write_guard.rs
@@ -39,7 +39,7 @@ pub fn root_and_write_guard(datum: &Datum,
                             expr_id: ast::NodeId,
                             derefs: uint) -> @mut Block {
     let key = root_map_key { id: expr_id, derefs: derefs };
-    debug!("write_guard::root_and_write_guard(key=%?)", key);
+    debug2!("write_guard::root_and_write_guard(key={:?})", key);
 
     // root the autoderef'd value, if necessary:
     //
@@ -66,7 +66,7 @@ pub fn return_to_mut(mut bcx: @mut Block,
                      bits_val_ref: ValueRef,
                      filename_val: ValueRef,
                      line_val: ValueRef) -> @mut Block {
-    debug!("write_guard::return_to_mut(root_key=%?, %s, %s, %s)",
+    debug2!("write_guard::return_to_mut(root_key={:?}, {}, {}, {})",
            root_key,
            bcx.to_str(),
            bcx.val_to_str(frozen_val_ref),
@@ -111,13 +111,13 @@ fn root(datum: &Datum,
     //! case, we will call this function, which will stash a copy
     //! away until we exit the scope `scope_id`.
 
-    debug!("write_guard::root(root_key=%?, root_info=%?, datum=%?)",
+    debug2!("write_guard::root(root_key={:?}, root_info={:?}, datum={:?})",
            root_key, root_info, datum.to_str(bcx.ccx()));
 
     if bcx.sess().trace() {
         trans_trace(
             bcx, None,
-            (fmt!("preserving until end of scope %d",
+            (format!("preserving until end of scope {}",
                   root_info.scope)).to_managed());
     }
 
@@ -184,7 +184,7 @@ fn root(datum: &Datum,
 fn perform_write_guard(datum: &Datum,
                        bcx: @mut Block,
                        span: Span) -> @mut Block {
-    debug!("perform_write_guard");
+    debug2!("perform_write_guard");
 
     let llval = datum.to_value_llval(bcx);
     let (filename, line) = filename_and_line_num_from_span(bcx, span);
diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index ed103f66915..ef6809c15c8 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -794,7 +794,7 @@ impl Vid for TyVid {
 }
 
 impl ToStr for TyVid {
-    fn to_str(&self) -> ~str { fmt!("<V%u>", self.to_uint()) }
+    fn to_str(&self) -> ~str { format!("<V{}>", self.to_uint()) }
 }
 
 impl Vid for IntVid {
@@ -802,7 +802,7 @@ impl Vid for IntVid {
 }
 
 impl ToStr for IntVid {
-    fn to_str(&self) -> ~str { fmt!("<VI%u>", self.to_uint()) }
+    fn to_str(&self) -> ~str { format!("<VI{}>", self.to_uint()) }
 }
 
 impl Vid for FloatVid {
@@ -810,7 +810,7 @@ impl Vid for FloatVid {
 }
 
 impl ToStr for FloatVid {
-    fn to_str(&self) -> ~str { fmt!("<VF%u>", self.to_uint()) }
+    fn to_str(&self) -> ~str { format!("<VF{}>", self.to_uint()) }
 }
 
 impl Vid for RegionVid {
@@ -818,7 +818,7 @@ impl Vid for RegionVid {
 }
 
 impl ToStr for RegionVid {
-    fn to_str(&self) -> ~str { fmt!("%?", self.id) }
+    fn to_str(&self) -> ~str { format!("{:?}", self.id) }
 }
 
 impl ToStr for FnSig {
@@ -1515,7 +1515,7 @@ pub fn fold_regions(
     fldr: &fn(r: Region, in_fn: bool) -> Region) -> t {
     fn do_fold(cx: ctxt, ty: t, in_fn: bool,
                fldr: &fn(Region, bool) -> Region) -> t {
-        debug!("do_fold(ty=%s, in_fn=%b)", ty_to_str(cx, ty), in_fn);
+        debug2!("do_fold(ty={}, in_fn={})", ty_to_str(cx, ty), in_fn);
         if !type_has_regions(ty) { return ty; }
         fold_regions_and_ty(
             cx, ty,
@@ -1656,7 +1656,7 @@ pub fn simd_type(cx: ctxt, ty: t) -> t {
             let fields = lookup_struct_fields(cx, did);
             lookup_field_type(cx, did, fields[0].id, substs)
         }
-        _ => fail!("simd_type called on invalid type")
+        _ => fail2!("simd_type called on invalid type")
     }
 }
 
@@ -1666,14 +1666,14 @@ pub fn simd_size(cx: ctxt, ty: t) -> uint {
             let fields = lookup_struct_fields(cx, did);
             fields.len()
         }
-        _ => fail!("simd_size called on invalid type")
+        _ => fail2!("simd_size called on invalid type")
     }
 }
 
 pub fn get_element_type(ty: t, i: uint) -> t {
     match get(ty).sty {
       ty_tup(ref ts) => return ts[i],
-      _ => fail!("get_element_type called on invalid type")
+      _ => fail2!("get_element_type called on invalid type")
     }
 }
 
@@ -1950,7 +1950,7 @@ impl ops::Sub<TypeContents,TypeContents> for TypeContents {
 
 impl ToStr for TypeContents {
     fn to_str(&self) -> ~str {
-        fmt!("TypeContents(%s)", self.bits.to_str_radix(2))
+        format!("TypeContents({})", self.bits.to_str_radix(2))
     }
 }
 
@@ -2324,7 +2324,7 @@ pub fn type_contents(cx: ctxt, ty: t) -> TypeContents {
 
         let mut tc = TC_ALL;
         do each_inherited_builtin_bound(cx, bounds, traits) |bound| {
-            debug!("tc = %s, bound = %?", tc.to_str(), bound);
+            debug2!("tc = {}, bound = {:?}", tc.to_str(), bound);
             tc = tc - match bound {
                 BoundStatic => TypeContents::nonstatic(cx),
                 BoundSend => TypeContents::nonsendable(cx),
@@ -2334,7 +2334,7 @@ pub fn type_contents(cx: ctxt, ty: t) -> TypeContents {
             };
         }
 
-        debug!("result = %s", tc.to_str());
+        debug2!("result = {}", tc.to_str());
         return tc;
 
         // Iterates over all builtin bounds on the type parameter def, including
@@ -2364,7 +2364,7 @@ pub fn type_moves_by_default(cx: ctxt, ty: t) -> bool {
 pub fn is_instantiable(cx: ctxt, r_ty: t) -> bool {
     fn type_requires(cx: ctxt, seen: &mut ~[DefId],
                      r_ty: t, ty: t) -> bool {
-        debug!("type_requires(%s, %s)?",
+        debug2!("type_requires({}, {})?",
                ::util::ppaux::ty_to_str(cx, r_ty),
                ::util::ppaux::ty_to_str(cx, ty));
 
@@ -2373,7 +2373,7 @@ pub fn is_instantiable(cx: ctxt, r_ty: t) -> bool {
                 subtypes_require(cx, seen, r_ty, ty)
         };
 
-        debug!("type_requires(%s, %s)? %b",
+        debug2!("type_requires({}, {})? {}",
                ::util::ppaux::ty_to_str(cx, r_ty),
                ::util::ppaux::ty_to_str(cx, ty),
                r);
@@ -2382,7 +2382,7 @@ pub fn is_instantiable(cx: ctxt, r_ty: t) -> bool {
 
     fn subtypes_require(cx: ctxt, seen: &mut ~[DefId],
                         r_ty: t, ty: t) -> bool {
-        debug!("subtypes_require(%s, %s)?",
+        debug2!("subtypes_require({}, {})?",
                ::util::ppaux::ty_to_str(cx, r_ty),
                ::util::ppaux::ty_to_str(cx, ty));
 
@@ -2456,7 +2456,7 @@ pub fn is_instantiable(cx: ctxt, r_ty: t) -> bool {
             }
         };
 
-        debug!("subtypes_require(%s, %s)? %b",
+        debug2!("subtypes_require({}, {})? {}",
                ::util::ppaux::ty_to_str(cx, r_ty),
                ::util::ppaux::ty_to_str(cx, ty),
                r);
@@ -2473,7 +2473,7 @@ pub fn type_structurally_contains(cx: ctxt,
                                   test: &fn(x: &sty) -> bool)
                                -> bool {
     let sty = &get(ty).sty;
-    debug!("type_structurally_contains: %s",
+    debug2!("type_structurally_contains: {}",
            ::util::ppaux::ty_to_str(cx, ty));
     if test(sty) { return true; }
     match *sty {
@@ -2786,18 +2786,18 @@ pub fn node_id_to_trait_ref(cx: ctxt, id: ast::NodeId) -> @ty::TraitRef {
     match cx.trait_refs.find(&id) {
        Some(&t) => t,
        None => cx.sess.bug(
-           fmt!("node_id_to_trait_ref: no trait ref for node `%s`",
+           format!("node_id_to_trait_ref: no trait ref for node `{}`",
                 ast_map::node_id_to_str(cx.items, id,
                                         token::get_ident_interner())))
     }
 }
 
 pub fn node_id_to_type(cx: ctxt, id: ast::NodeId) -> t {
-    //printfln!("%?/%?", id, cx.node_types.len());
+    //printfln!("{:?}/{:?}", id, cx.node_types.len());
     match cx.node_types.find(&(id as uint)) {
        Some(&t) => t,
        None => cx.sess.bug(
-           fmt!("node_id_to_type: no type for node `%s`",
+           format!("node_id_to_type: no type for node `{}`",
                 ast_map::node_id_to_str(cx.items, id,
                                         token::get_ident_interner())))
     }
@@ -2820,7 +2820,7 @@ pub fn ty_fn_sig(fty: t) -> FnSig {
         ty_bare_fn(ref f) => f.sig.clone(),
         ty_closure(ref f) => f.sig.clone(),
         ref s => {
-            fail!("ty_fn_sig() called on non-fn type: %?", s)
+            fail2!("ty_fn_sig() called on non-fn type: {:?}", s)
         }
     }
 }
@@ -2831,7 +2831,7 @@ pub fn ty_fn_args(fty: t) -> ~[t] {
         ty_bare_fn(ref f) => f.sig.inputs.clone(),
         ty_closure(ref f) => f.sig.inputs.clone(),
         ref s => {
-            fail!("ty_fn_args() called on non-fn type: %?", s)
+            fail2!("ty_fn_args() called on non-fn type: {:?}", s)
         }
     }
 }
@@ -2840,7 +2840,7 @@ pub fn ty_closure_sigil(fty: t) -> Sigil {
     match get(fty).sty {
         ty_closure(ref f) => f.sigil,
         ref s => {
-            fail!("ty_closure_sigil() called on non-closure type: %?", s)
+            fail2!("ty_closure_sigil() called on non-closure type: {:?}", s)
         }
     }
 }
@@ -2850,7 +2850,7 @@ pub fn ty_fn_purity(fty: t) -> ast::purity {
         ty_bare_fn(ref f) => f.purity,
         ty_closure(ref f) => f.purity,
         ref s => {
-            fail!("ty_fn_purity() called on non-fn type: %?", s)
+            fail2!("ty_fn_purity() called on non-fn type: {:?}", s)
         }
     }
 }
@@ -2860,7 +2860,7 @@ pub fn ty_fn_ret(fty: t) -> t {
         ty_bare_fn(ref f) => f.sig.output,
         ty_closure(ref f) => f.sig.output,
         ref s => {
-            fail!("ty_fn_ret() called on non-fn type: %?", s)
+            fail2!("ty_fn_ret() called on non-fn type: {:?}", s)
         }
     }
 }
@@ -2877,7 +2877,7 @@ pub fn ty_vstore(ty: t) -> vstore {
     match get(ty).sty {
         ty_evec(_, vstore) => vstore,
         ty_estr(vstore) => vstore,
-        ref s => fail!("ty_vstore() called on invalid sty: %?", s)
+        ref s => fail2!("ty_vstore() called on invalid sty: {:?}", s)
     }
 }
 
@@ -2891,7 +2891,7 @@ pub fn ty_region(tcx: ctxt,
         ref s => {
             tcx.sess.span_bug(
                 span,
-                fmt!("ty_region() invoked on in appropriate ty: %?", s));
+                format!("ty_region() invoked on in appropriate ty: {:?}", s));
         }
     }
 }
@@ -2902,7 +2902,7 @@ pub fn replace_fn_sig(cx: ctxt, fsty: &sty, new_sig: FnSig) -> t {
         ty_closure(ref f) => mk_closure(cx, ClosureTy {sig: new_sig, ..*f}),
         ref s => {
             cx.sess.bug(
-                fmt!("ty_fn_sig() called on non-fn type: %?", s));
+                format!("ty_fn_sig() called on non-fn type: {:?}", s));
         }
     }
 }
@@ -2921,8 +2921,8 @@ pub fn replace_closure_return_type(tcx: ctxt, fn_type: t, ret_type: t) -> t {
             })
         }
         _ => {
-            tcx.sess.bug(fmt!(
-                "replace_fn_ret() invoked with non-fn-type: %s",
+            tcx.sess.bug(format!(
+                "replace_fn_ret() invoked with non-fn-type: {}",
                 ty_to_str(tcx, fn_type)));
         }
     }
@@ -3003,7 +3003,7 @@ pub fn adjust_ty(cx: ctxt,
                 }
                 ref b => {
                     cx.sess.bug(
-                        fmt!("add_env adjustment on non-bare-fn: %?", b));
+                        format!("add_env adjustment on non-bare-fn: {:?}", b));
                 }
             }
         }
@@ -3018,7 +3018,7 @@ pub fn adjust_ty(cx: ctxt,
                         None => {
                             cx.sess.span_bug(
                                 span,
-                                fmt!("The %uth autoderef failed: %s",
+                                format!("The {}th autoderef failed: {}",
                                      i, ty_to_str(cx,
                                                   adjusted_ty)));
                         }
@@ -3075,7 +3075,7 @@ pub fn adjust_ty(cx: ctxt,
             ref s => {
                 cx.sess.span_bug(
                     span,
-                    fmt!("borrow-vec associated with bad sty: %?",
+                    format!("borrow-vec associated with bad sty: {:?}",
                          s));
             }
         }
@@ -3094,7 +3094,7 @@ pub fn adjust_ty(cx: ctxt,
             ref s => {
                 cx.sess.span_bug(
                     span,
-                    fmt!("borrow-fn associated with bad sty: %?",
+                    format!("borrow-fn associated with bad sty: {:?}",
                          s));
             }
         }
@@ -3110,7 +3110,7 @@ pub fn adjust_ty(cx: ctxt,
             ref s => {
                 cx.sess.span_bug(
                     span,
-                    fmt!("borrow-trait-obj associated with bad sty: %?",
+                    format!("borrow-trait-obj associated with bad sty: {:?}",
                          s));
             }
         }
@@ -3185,8 +3185,8 @@ pub fn resolve_expr(tcx: ctxt, expr: &ast::Expr) -> ast::Def {
     match tcx.def_map.find(&expr.id) {
         Some(&def) => def,
         None => {
-            tcx.sess.span_bug(expr.span, fmt!(
-                "No def-map entry for expr %?", expr.id));
+            tcx.sess.span_bug(expr.span, format!(
+                "No def-map entry for expr {:?}", expr.id));
         }
     }
 }
@@ -3244,8 +3244,8 @@ pub fn expr_kind(tcx: ctxt,
                 ast::DefSelf(*) => LvalueExpr,
 
                 def => {
-                    tcx.sess.span_bug(expr.span, fmt!(
-                        "Uncategorized def for expr %?: %?",
+                    tcx.sess.span_bug(expr.span, format!(
+                        "Uncategorized def for expr {:?}: {:?}",
                         expr.id, def));
                 }
             }
@@ -3311,7 +3311,7 @@ pub fn expr_kind(tcx: ctxt,
             RvalueStmtExpr
         }
 
-        ast::ExprForLoop(*) => fail!("non-desugared expr_for_loop"),
+        ast::ExprForLoop(*) => fail2!("non-desugared expr_for_loop"),
 
         ast::ExprLogLevel |
         ast::ExprLit(_) | // Note: lit_str is carved out above
@@ -3339,7 +3339,7 @@ pub fn stmt_node_id(s: &ast::Stmt) -> ast::NodeId {
       ast::StmtDecl(_, id) | StmtExpr(_, id) | StmtSemi(_, id) => {
         return id;
       }
-      ast::StmtMac(*) => fail!("unexpanded macro in trans")
+      ast::StmtMac(*) => fail2!("unexpanded macro in trans")
     }
 }
 
@@ -3353,8 +3353,8 @@ pub fn field_idx_strict(tcx: ty::ctxt, name: ast::Name, fields: &[field])
                      -> uint {
     let mut i = 0u;
     for f in fields.iter() { if f.ident.name == name { return i; } i += 1u; }
-    tcx.sess.bug(fmt!(
-        "No field named `%s` found in the list of fields `%?`",
+    tcx.sess.bug(format!(
+        "No field named `{}` found in the list of fields `{:?}`",
         token::interner_get(name),
         fields.map(|f| tcx.sess.str_of(f.ident))));
 }
@@ -3418,7 +3418,7 @@ pub fn ty_sort_str(cx: ctxt, t: t) -> ~str {
         ::util::ppaux::ty_to_str(cx, t)
       }
 
-      ty_enum(id, _) => fmt!("enum %s", item_path_str(cx, id)),
+      ty_enum(id, _) => format!("enum {}", item_path_str(cx, id)),
       ty_box(_) => ~"@-ptr",
       ty_uniq(_) => ~"~-ptr",
       ty_evec(_, _) => ~"vector",
@@ -3427,8 +3427,8 @@ pub fn ty_sort_str(cx: ctxt, t: t) -> ~str {
       ty_rptr(_, _) => ~"&-ptr",
       ty_bare_fn(_) => ~"extern fn",
       ty_closure(_) => ~"fn",
-      ty_trait(id, _, _, _, _) => fmt!("trait %s", item_path_str(cx, id)),
-      ty_struct(id, _) => fmt!("struct %s", item_path_str(cx, id)),
+      ty_trait(id, _, _, _, _) => format!("trait {}", item_path_str(cx, id)),
+      ty_struct(id, _) => format!("struct {}", item_path_str(cx, id)),
       ty_tup(_) => ~"tuple",
       ty_infer(TyVar(_)) => ~"inferred type",
       ty_infer(IntVar(_)) => ~"integral variable",
@@ -3461,19 +3461,19 @@ pub fn type_err_to_str(cx: ctxt, err: &type_err) -> ~str {
     match *err {
         terr_mismatch => ~"types differ",
         terr_purity_mismatch(values) => {
-            fmt!("expected %s fn but found %s fn",
+            format!("expected {} fn but found {} fn",
                  values.expected.to_str(), values.found.to_str())
         }
         terr_abi_mismatch(values) => {
-            fmt!("expected %s fn but found %s fn",
+            format!("expected {} fn but found {} fn",
                  values.expected.to_str(), values.found.to_str())
         }
         terr_onceness_mismatch(values) => {
-            fmt!("expected %s fn but found %s fn",
+            format!("expected {} fn but found {} fn",
                  values.expected.to_str(), values.found.to_str())
         }
         terr_sigil_mismatch(values) => {
-            fmt!("expected %s closure, found %s closure",
+            format!("expected {} closure, found {} closure",
                  values.expected.to_str(),
                  values.found.to_str())
         }
@@ -3483,97 +3483,97 @@ pub fn type_err_to_str(cx: ctxt, err: &type_err) -> ~str {
         terr_ptr_mutability => ~"pointers differ in mutability",
         terr_ref_mutability => ~"references differ in mutability",
         terr_ty_param_size(values) => {
-            fmt!("expected a type with %u type params \
-                  but found one with %u type params",
+            format!("expected a type with {} type params \
+                  but found one with {} type params",
                  values.expected, values.found)
         }
         terr_tuple_size(values) => {
-            fmt!("expected a tuple with %u elements \
-                  but found one with %u elements",
+            format!("expected a tuple with {} elements \
+                  but found one with {} elements",
                  values.expected, values.found)
         }
         terr_record_size(values) => {
-            fmt!("expected a record with %u fields \
-                  but found one with %u fields",
+            format!("expected a record with {} fields \
+                  but found one with {} fields",
                  values.expected, values.found)
         }
         terr_record_mutability => {
             ~"record elements differ in mutability"
         }
         terr_record_fields(values) => {
-            fmt!("expected a record with field `%s` but found one with field \
-                  `%s`",
+            format!("expected a record with field `{}` but found one with field \
+                  `{}`",
                  cx.sess.str_of(values.expected),
                  cx.sess.str_of(values.found))
         }
         terr_arg_count => ~"incorrect number of function parameters",
         terr_regions_does_not_outlive(*) => {
-            fmt!("lifetime mismatch")
+            format!("lifetime mismatch")
         }
         terr_regions_not_same(*) => {
-            fmt!("lifetimes are not the same")
+            format!("lifetimes are not the same")
         }
         terr_regions_no_overlap(*) => {
-            fmt!("lifetimes do not intersect")
+            format!("lifetimes do not intersect")
         }
         terr_regions_insufficiently_polymorphic(br, _) => {
-            fmt!("expected bound lifetime parameter %s, \
+            format!("expected bound lifetime parameter {}, \
                   but found concrete lifetime",
                  bound_region_ptr_to_str(cx, br))
         }
         terr_regions_overly_polymorphic(br, _) => {
-            fmt!("expected concrete lifetime, \
-                  but found bound lifetime parameter %s",
+            format!("expected concrete lifetime, \
+                  but found bound lifetime parameter {}",
                  bound_region_ptr_to_str(cx, br))
         }
         terr_vstores_differ(k, ref values) => {
-            fmt!("%s storage differs: expected %s but found %s",
+            format!("{} storage differs: expected {} but found {}",
                  terr_vstore_kind_to_str(k),
                  vstore_to_str(cx, (*values).expected),
                  vstore_to_str(cx, (*values).found))
         }
         terr_trait_stores_differ(_, ref values) => {
-            fmt!("trait storage differs: expected %s but found %s",
+            format!("trait storage differs: expected {} but found {}",
                  trait_store_to_str(cx, (*values).expected),
                  trait_store_to_str(cx, (*values).found))
         }
         terr_in_field(err, fname) => {
-            fmt!("in field `%s`, %s", cx.sess.str_of(fname),
+            format!("in field `{}`, {}", cx.sess.str_of(fname),
                  type_err_to_str(cx, err))
         }
         terr_sorts(values) => {
-            fmt!("expected %s but found %s",
+            format!("expected {} but found {}",
                  ty_sort_str(cx, values.expected),
                  ty_sort_str(cx, values.found))
         }
         terr_traits(values) => {
-            fmt!("expected trait %s but found trait %s",
+            format!("expected trait {} but found trait {}",
                  item_path_str(cx, values.expected),
                  item_path_str(cx, values.found))
         }
         terr_builtin_bounds(values) => {
             if values.expected.is_empty() {
-                fmt!("expected no bounds but found `%s`",
+                format!("expected no bounds but found `{}`",
                      values.found.user_string(cx))
             } else if values.found.is_empty() {
-                fmt!("expected bounds `%s` but found no bounds",
+                format!("expected bounds `{}` but found no bounds",
                      values.expected.user_string(cx))
             } else {
-                fmt!("expected bounds `%s` but found bounds `%s`",
+                format!("expected bounds `{}` but found bounds `{}`",
                      values.expected.user_string(cx),
                      values.found.user_string(cx))
             }
         }
         terr_integer_as_char => {
-            fmt!("expected an integral type but found char")
+            format!("expected an integral type but found char")
         }
         terr_int_mismatch(ref values) => {
-            fmt!("expected %s but found %s",
+            format!("expected {} but found {}",
                  values.expected.to_str(),
                  values.found.to_str())
         }
         terr_float_mismatch(ref values) => {
-            fmt!("expected %s but found %s",
+            format!("expected {} but found {}",
                  values.expected.to_str(),
                  values.found.to_str())
         }
@@ -3633,7 +3633,7 @@ pub fn provided_trait_methods(cx: ctxt, id: ast::DefId) -> ~[@Method] {
                 match ast_util::split_trait_methods(*ms) {
                    (_, p) => p.map(|m| method(cx, ast_util::local_def(m.id)))
                 },
-            _ => cx.sess.bug(fmt!("provided_trait_methods: %? is not a trait",
+            _ => cx.sess.bug(format!("provided_trait_methods: {:?} is not a trait",
                                   id))
         }
     } else {
@@ -3690,7 +3690,7 @@ fn lookup_locally_or_in_crate_store<V:Clone>(
     }
 
     if def_id.crate == ast::LOCAL_CRATE {
-        fail!("No def'n found for %? in tcx.%s", def_id, descr);
+        fail2!("No def'n found for {:?} in tcx.{}", def_id, descr);
     }
     let v = load_external();
     map.insert(def_id, v.clone());
@@ -3733,7 +3733,7 @@ pub fn impl_trait_ref(cx: ctxt, id: ast::DefId) -> Option<@TraitRef> {
         None => {}
     }
     let ret = if id.crate == ast::LOCAL_CRATE {
-        debug!("(impl_trait_ref) searching for trait impl %?", id);
+        debug2!("(impl_trait_ref) searching for trait impl {:?}", id);
         match cx.items.find(&id.node) {
             Some(&ast_map::node_item(@ast::item {
                                      node: ast::item_impl(_, ref opt_trait, _, _),
@@ -3979,7 +3979,7 @@ pub fn item_path(cx: ctxt, id: ast::DefId) -> ast_map::path {
           }
 
           ref node => {
-            cx.sess.bug(fmt!("cannot find item_path for node %?", node));
+            cx.sess.bug(format!("cannot find item_path for node {:?}", node));
           }
         }
     }
@@ -4031,7 +4031,7 @@ pub fn enum_variants(cx: ctxt, id: ast::DefId) -> @~[@VariantInfo] {
                             cx.sess.span_err(e.span, "expected signed integer constant");
                         }
                         Err(ref err) => {
-                            cx.sess.span_err(e.span, fmt!("expected constant: %s", (*err)));
+                            cx.sess.span_err(e.span, format!("expected constant: {}", (*err)));
                         }
                     },
                     None => {}
@@ -4111,7 +4111,7 @@ pub fn has_attr(tcx: ctxt, did: DefId, attr: &str) -> bool {
                     attrs: ref attrs,
                     _
                 }, _)) => attr::contains_name(*attrs, attr),
-            _ => tcx.sess.bug(fmt!("has_attr: %? is not an item",
+            _ => tcx.sess.bug(format!("has_attr: {:?} is not an item",
                                    did))
         }
     } else {
@@ -4182,7 +4182,7 @@ pub fn lookup_struct_fields(cx: ctxt, did: ast::DefId) -> ~[field_ty] {
        }
        _ => {
            cx.sess.bug(
-               fmt!("struct ID not bound to an item: %s",
+               format!("struct ID not bound to an item: {}",
                     ast_map::node_id_to_str(cx.items, did.node,
                                             token::get_ident_interner())));
        }
@@ -4486,7 +4486,7 @@ pub fn each_bound_trait_and_supertraits(tcx: ctxt,
 
         // Add the given trait ty to the hash map
         while i < trait_refs.len() {
-            debug!("each_bound_trait_and_supertraits(i=%?, trait_ref=%s)",
+            debug2!("each_bound_trait_and_supertraits(i={:?}, trait_ref={})",
                    i, trait_refs[i].repr(tcx));
 
             if !f(trait_refs[i]) {
@@ -4496,7 +4496,7 @@ pub fn each_bound_trait_and_supertraits(tcx: ctxt,
             // Add supertraits to supertrait_set
             let supertrait_refs = trait_ref_supertraits(tcx, trait_refs[i]);
             for &supertrait_ref in supertrait_refs.iter() {
-                debug!("each_bound_trait_and_supertraits(supertrait_ref=%s)",
+                debug2!("each_bound_trait_and_supertraits(supertrait_ref={})",
                        supertrait_ref.repr(tcx));
 
                 let d_id = supertrait_ref.def_id;
diff --git a/src/librustc/middle/typeck/astconv.rs b/src/librustc/middle/typeck/astconv.rs
index 024010e40df..91bb4df3017 100644
--- a/src/librustc/middle/typeck/astconv.rs
+++ b/src/librustc/middle/typeck/astconv.rs
@@ -92,12 +92,12 @@ pub fn get_region_reporting_err(
         result::Err(ref e) => {
             let descr = match a_r {
                 &None => ~"anonymous lifetime",
-                &Some(ref a) => fmt!("lifetime %s",
+                &Some(ref a) => format!("lifetime {}",
                                 lifetime_to_str(a, tcx.sess.intr()))
             };
             tcx.sess.span_err(
                 span,
-                fmt!("Illegal %s: %s",
+                format!("Illegal {}: {}",
                      descr, e.msg));
             e.replacement
         }
@@ -157,7 +157,7 @@ fn ast_path_substs<AC:AstConv,RS:RegionScope + Clone + 'static>(
         (&None, &Some(_)) => {
             tcx.sess.span_err(
                 path.span,
-                fmt!("no region bound is allowed on `%s`, \
+                format!("no region bound is allowed on `{}`, \
                       which is not declared as containing region pointers",
                      ty::item_path_str(tcx, def_id)));
             opt_vec::Empty
@@ -182,7 +182,7 @@ fn ast_path_substs<AC:AstConv,RS:RegionScope + Clone + 'static>(
     if decl_generics.type_param_defs.len() != supplied_type_parameter_count {
         this.tcx().sess.span_fatal(
             path.span,
-            fmt!("wrong number of type arguments: expected %u but found %u",
+            format!("wrong number of type arguments: expected {} but found {}",
                  decl_generics.type_param_defs.len(),
                  supplied_type_parameter_count));
     }
@@ -428,7 +428,7 @@ pub fn ast_ty_to_ty<AC:AstConv, RS:RegionScope + Clone + 'static>(
       ast::ty_path(ref path, ref bounds, id) => {
         let a_def = match tcx.def_map.find(&id) {
           None => tcx.sess.span_fatal(
-              ast_ty.span, fmt!("unbound path %s",
+              ast_ty.span, format!("unbound path {}",
                                 path_to_str(path, tcx.sess.intr()))),
           Some(&d) => d
         };
@@ -446,8 +446,8 @@ pub fn ast_ty_to_ty<AC:AstConv, RS:RegionScope + Clone + 'static>(
               let path_str = path_to_str(path, tcx.sess.intr());
               tcx.sess.span_err(
                   ast_ty.span,
-                  fmt!("reference to trait `%s` where a type is expected; \
-                        try `@%s`, `~%s`, or `&%s`",
+                  format!("reference to trait `{}` where a type is expected; \
+                        try `@{}`, `~{}`, or `&{}`",
                        path_str, path_str, path_str, path_str));
               ty::mk_err()
           }
@@ -498,7 +498,7 @@ pub fn ast_ty_to_ty<AC:AstConv, RS:RegionScope + Clone + 'static>(
           }
           _ => {
             tcx.sess.span_fatal(ast_ty.span,
-                                fmt!("found value name used as a type: %?", a_def));
+                                format!("found value name used as a type: {:?}", a_def));
           }
         }
       }
@@ -521,8 +521,7 @@ pub fn ast_ty_to_ty<AC:AstConv, RS:RegionScope + Clone + 'static>(
           Err(ref r) => {
             tcx.sess.span_fatal(
                 ast_ty.span,
-                fmt!("expected constant expr for vector length: %s",
-                     *r));
+                format!("expected constant expr for vector length: {}", *r));
           }
         }
       }
@@ -583,7 +582,7 @@ pub fn bound_lifetimes<AC:AstConv>(
         if special_idents.iter().any(|&i| i == ast_lifetime.ident) {
             this.tcx().sess.span_err(
                 ast_lifetime.span,
-                fmt!("illegal lifetime parameter name: `%s`",
+                format!("illegal lifetime parameter name: `{}`",
                      lifetime_to_str(ast_lifetime, this.tcx().sess.intr())));
         } else {
             bound_lifetime_names.push(ast_lifetime.ident);
@@ -637,7 +636,7 @@ fn ty_of_method_or_bare_fn<AC:AstConv,RS:RegionScope + Clone + 'static>(
     opt_self_info: Option<&SelfInfo>,
     decl: &ast::fn_decl) -> (Option<Option<ty::t>>, ty::BareFnTy)
 {
-    debug!("ty_of_bare_fn");
+    debug2!("ty_of_bare_fn");
 
     // new region names that appear inside of the fn decl are bound to
     // that function type
@@ -718,7 +717,7 @@ pub fn ty_of_closure<AC:AstConv,RS:RegionScope + Clone + 'static>(
     // names or they are provided, but not both.
     assert!(lifetimes.is_empty() || expected_sig.is_none());
 
-    debug!("ty_of_fn_decl");
+    debug2!("ty_of_fn_decl");
     let _i = indenter();
 
     // resolve the function bound region in the original region
@@ -807,7 +806,7 @@ fn conv_builtin_bounds(tcx: ty::ctxt, ast_bounds: &Option<OptVec<ast::TyParamBou
                         }
                         tcx.sess.span_fatal(
                             b.path.span,
-                            fmt!("only the builtin traits can be used \
+                            format!("only the builtin traits can be used \
                                   as closure or object bounds"));
                     }
                     ast::RegionTyParamBound => {
diff --git a/src/librustc/middle/typeck/check/_match.rs b/src/librustc/middle/typeck/check/_match.rs
index 606b0255cd7..f022f2b3c4b 100644
--- a/src/librustc/middle/typeck/check/_match.rs
+++ b/src/librustc/middle/typeck/check/_match.rs
@@ -166,7 +166,7 @@ pub fn check_pat_variant(pcx: &pat_ctxt, pat: @ast::Pat, path: &ast::Path,
                     fcx.infcx().type_error_message_str_with_expected(pat.span,
                                                        |expected, actual| {
                                                        expected.map_move_default(~"", |e| {
-                        fmt!("mismatched types: expected `%s` but found %s",
+                        format!("mismatched types: expected `{}` but found {}",
                              e, actual)})},
                              Some(expected), ~"a structure pattern",
                              None);
@@ -215,7 +215,7 @@ pub fn check_pat_variant(pcx: &pat_ctxt, pat: @ast::Pat, path: &ast::Path,
             fcx.infcx().type_error_message_str_with_expected(pat.span,
                                                |expected, actual| {
                                                expected.map_move_default(~"", |e| {
-                    fmt!("mismatched types: expected `%s` but found %s",
+                    format!("mismatched types: expected `{}` but found {}",
                          e, actual)})},
                     Some(expected), ~"an enum or structure pattern",
                     None);
@@ -241,7 +241,7 @@ pub fn check_pat_variant(pcx: &pat_ctxt, pat: @ast::Pat, path: &ast::Path,
     if arg_len > 0 {
         // N-ary variant.
         if arg_len != subpats_len {
-            let s = fmt!("this pattern has %u field%s, but the corresponding %s has %u field%s",
+            let s = format!("this pattern has {} field{}, but the corresponding {} has {} field{}",
                          subpats_len,
                          if subpats_len == 1u { ~"" } else { ~"s" },
                          kind_name,
@@ -260,7 +260,7 @@ pub fn check_pat_variant(pcx: &pat_ctxt, pat: @ast::Pat, path: &ast::Path,
         }
     } else if subpats_len > 0 {
         tcx.sess.span_err(pat.span,
-                          fmt!("this pattern has %u field%s, but the corresponding %s has no \
+                          format!("this pattern has {} field{}, but the corresponding {} has no \
                                 fields",
                                subpats_len,
                                if subpats_len == 1u { "" } else { "s" },
@@ -319,7 +319,7 @@ pub fn check_struct_pat_fields(pcx: &pat_ctxt,
                 // up its type won't fail
                 check_pat(pcx, field.pat, ty::mk_err());
                 tcx.sess.span_err(span,
-                    fmt!("struct `%s` does not have a field named `%s`",
+                    format!("struct `{}` does not have a field named `{}`",
                          name,
                          tcx.sess.str_of(field.ident)));
             }
@@ -333,7 +333,7 @@ pub fn check_struct_pat_fields(pcx: &pat_ctxt,
                 loop;
             }
             tcx.sess.span_err(span,
-                              fmt!("pattern does not mention field `%s`",
+                              format!("pattern does not mention field `{}`",
                                    token::interner_get(field.name)));
         }
     }
@@ -358,7 +358,7 @@ pub fn check_struct_pat(pcx: &pat_ctxt, pat_id: ast::NodeId, span: Span,
         Some(&ast::DefStruct(*)) | Some(&ast::DefVariant(*)) => {
             let name = pprust::path_to_str(path, tcx.sess.intr());
             tcx.sess.span_err(span,
-                              fmt!("mismatched types: expected `%s` but found `%s`",
+                              format!("mismatched types: expected `{}` but found `{}`",
                                    fcx.infcx().ty_to_str(expected),
                                    name));
         }
@@ -396,8 +396,8 @@ pub fn check_struct_like_enum_variant_pat(pcx: &pat_ctxt,
         Some(&ast::DefStruct(*)) | Some(&ast::DefVariant(*)) => {
             let name = pprust::path_to_str(path, tcx.sess.intr());
             tcx.sess.span_err(span,
-                              fmt!("mismatched types: expected `%s` but \
-                                    found `%s`",
+                              format!("mismatched types: expected `{}` but \
+                                    found `{}`",
                                    fcx.infcx().ty_to_str(expected),
                                    name));
         }
@@ -428,8 +428,8 @@ pub fn check_pat(pcx: &pat_ctxt, pat: @ast::Pat, expected: ty::t) {
             fcx.infcx().resolve_type_vars_if_possible(fcx.expr_ty(begin));
         let e_ty =
             fcx.infcx().resolve_type_vars_if_possible(fcx.expr_ty(end));
-        debug!("pat_range beginning type: %?", b_ty);
-        debug!("pat_range ending type: %?", e_ty);
+        debug2!("pat_range beginning type: {:?}", b_ty);
+        debug2!("pat_range ending type: {:?}", e_ty);
         if !require_same_types(
             tcx, Some(fcx.infcx()), false, pat.span, b_ty, e_ty,
             || ~"mismatched types in range")
@@ -488,7 +488,7 @@ pub fn check_pat(pcx: &pat_ctxt, pat: @ast::Pat, expected: ty::t) {
         }
         fcx.write_ty(pat.id, typ);
 
-        debug!("(checking match) writing type for pat id %d", pat.id);
+        debug2!("(checking match) writing type for pat id {}", pat.id);
 
         match sub {
           Some(p) => check_pat(pcx, p, expected),
@@ -520,7 +520,7 @@ pub fn check_pat(pcx: &pat_ctxt, pat: @ast::Pat, expected: ty::t) {
                fcx.infcx().type_error_message_str_with_expected(pat.span,
                                                                 |expected, actual| {
                             expected.map_move_default(~"", |e| {
-                                    fmt!("mismatched types: expected `%s` but found %s",
+                                    format!("mismatched types: expected `{}` but found {}",
                                          e, actual)})},
                                          Some(expected), ~"a structure pattern",
                                          None);
@@ -567,7 +567,7 @@ pub fn check_pat(pcx: &pat_ctxt, pat: @ast::Pat, expected: ty::t) {
                 // See [Note-Type-error-reporting] in middle/typeck/infer/mod.rs
                 fcx.infcx().type_error_message_str_with_expected(pat.span, |expected, actual| {
                 expected.map_move_default(~"", |e| {
-                    fmt!("mismatched types: expected `%s` but found %s",
+                    format!("mismatched types: expected `{}` but found {}",
                                      e, actual)})}, Some(expected), ~"tuple", Some(&type_error));
                 fcx.write_error(pat.id);
             }
@@ -617,7 +617,7 @@ pub fn check_pat(pcx: &pat_ctxt, pat: @ast::Pat, expected: ty::t) {
                   pat.span,
                   |expected, actual| {
                       expected.map_move_default(~"", |e| {
-                          fmt!("mismatched types: expected `%s` but found %s",
+                          format!("mismatched types: expected `{}` but found {}",
                                e, actual)})},
                   Some(expected),
                   ~"a vector pattern",
@@ -676,10 +676,10 @@ pub fn check_pointer_pat(pcx: &pat_ctxt,
                 span,
                 |expected, actual| {
                     expected.map_move_default(~"", |e| {
-                        fmt!("mismatched types: expected `%s` but found %s",
+                        format!("mismatched types: expected `{}` but found {}",
                              e, actual)})},
                 Some(expected),
-                fmt!("%s pattern", match pointer_kind {
+                format!("{} pattern", match pointer_kind {
                     Managed => "an @-box",
                     Send => "a ~-box",
                     Borrowed => "an &-pointer"
diff --git a/src/librustc/middle/typeck/check/method.rs b/src/librustc/middle/typeck/check/method.rs
index 3cc93d3fea9..a4538c961fd 100644
--- a/src/librustc/middle/typeck/check/method.rs
+++ b/src/librustc/middle/typeck/check/method.rs
@@ -151,18 +151,18 @@ pub fn lookup(
     };
 
     let self_ty = structurally_resolved_type(fcx, self_expr.span, self_ty);
-    debug!("method lookup(self_ty=%s, expr=%s, self_expr=%s)",
+    debug2!("method lookup(self_ty={}, expr={}, self_expr={})",
            self_ty.repr(fcx.tcx()), expr.repr(fcx.tcx()),
            self_expr.repr(fcx.tcx()));
 
-    debug!("searching inherent candidates");
+    debug2!("searching inherent candidates");
     lcx.push_inherent_candidates(self_ty);
     let mme = lcx.search(self_ty);
     if mme.is_some() {
         return mme;
     }
 
-    debug!("searching extension candidates");
+    debug2!("searching extension candidates");
     lcx.reset_candidates();
     lcx.push_bound_candidates(self_ty);
     lcx.push_extension_candidates();
@@ -215,7 +215,7 @@ impl<'self> LookupContext<'self> {
         let mut self_ty = self_ty;
         let mut autoderefs = 0;
         loop {
-            debug!("loop: self_ty=%s autoderefs=%u",
+            debug2!("loop: self_ty={} autoderefs={}",
                    self.ty_to_str(self_ty), autoderefs);
 
             match self.deref_args {
@@ -397,7 +397,7 @@ impl<'self> LookupContext<'self> {
     fn push_inherent_candidates_from_object(&self,
                                             did: DefId,
                                             substs: &ty::substs) {
-        debug!("push_inherent_candidates_from_object(did=%s, substs=%s)",
+        debug2!("push_inherent_candidates_from_object(did={}, substs={})",
                self.did_to_str(did),
                substs_to_str(self.tcx(), substs));
         let _indenter = indenter();
@@ -446,7 +446,7 @@ impl<'self> LookupContext<'self> {
     fn push_inherent_candidates_from_param(&self,
                                            rcvr_ty: ty::t,
                                            param_ty: param_ty) {
-        debug!("push_inherent_candidates_from_param(param_ty=%?)",
+        debug2!("push_inherent_candidates_from_param(param_ty={:?})",
                param_ty);
         let _indenter = indenter();
 
@@ -456,7 +456,7 @@ impl<'self> LookupContext<'self> {
             None => {
                 tcx.sess.span_bug(
                     self.expr.span,
-                    fmt!("No param def for %?", param_ty));
+                    format!("No param def for {:?}", param_ty));
             }
         };
 
@@ -523,11 +523,11 @@ impl<'self> LookupContext<'self> {
                     let cand = mk_cand(bound_trait_ref, method,
                                        pos, this_bound_idx);
 
-                    debug!("pushing inherent candidate for param: %?", cand);
+                    debug2!("pushing inherent candidate for param: {:?}", cand);
                     self.inherent_candidates.push(cand);
                 }
                 None => {
-                    debug!("trait doesn't contain method: %?",
+                    debug2!("trait doesn't contain method: {:?}",
                     bound_trait_ref.def_id);
                     // check next trait or bound
                 }
@@ -557,7 +557,7 @@ impl<'self> LookupContext<'self> {
         if !self.impl_dups.insert(impl_info.did) {
             return; // already visited
         }
-        debug!("push_candidates_from_impl: %s %s %s",
+        debug2!("push_candidates_from_impl: {} {} {}",
                token::interner_get(self.m_name),
                impl_info.ident.repr(self.tcx()),
                impl_info.methods.map(|m| m.ident).repr(self.tcx()));
@@ -603,8 +603,8 @@ impl<'self> LookupContext<'self> {
         match self.search_for_method(self_ty) {
             None => None,
             Some(mme) => {
-                debug!("(searching for autoderef'd method) writing \
-                       adjustment (%u) to %d",
+                debug2!("(searching for autoderef'd method) writing \
+                       adjustment ({}) to {}",
                        autoderefs,
                        self.self_expr.id);
                 self.fcx.write_adjustment(self.self_expr.id, @autoadjust);
@@ -795,7 +795,7 @@ impl<'self> LookupContext<'self> {
 
             ty_opaque_closure_ptr(_) | ty_unboxed_vec(_) |
             ty_opaque_box | ty_type | ty_infer(TyVar(_)) => {
-                self.bug(fmt!("Unexpected type: %s",
+                self.bug(format!("Unexpected type: {}",
                               self.ty_to_str(self_ty)));
             }
         }
@@ -832,14 +832,14 @@ impl<'self> LookupContext<'self> {
 
     fn search_for_method(&self, rcvr_ty: ty::t)
                              -> Option<method_map_entry> {
-        debug!("search_for_method(rcvr_ty=%s)", self.ty_to_str(rcvr_ty));
+        debug2!("search_for_method(rcvr_ty={})", self.ty_to_str(rcvr_ty));
         let _indenter = indenter();
 
         // I am not sure that inherent methods should have higher
         // priority, but it is necessary ATM to handle some of the
         // existing code.
 
-        debug!("searching inherent candidates");
+        debug2!("searching inherent candidates");
         match self.consider_candidates(rcvr_ty, self.inherent_candidates) {
             None => {}
             Some(mme) => {
@@ -847,7 +847,7 @@ impl<'self> LookupContext<'self> {
             }
         }
 
-        debug!("searching extension candidates");
+        debug2!("searching extension candidates");
         match self.consider_candidates(rcvr_ty, self.extension_candidates) {
             None => {
                 return None;
@@ -896,7 +896,7 @@ impl<'self> LookupContext<'self> {
             let mut j = i + 1;
             while j < candidates.len() {
                 let candidate_b = &candidates[j];
-                debug!("attempting to merge %? and %?",
+                debug2!("attempting to merge {:?} and {:?}",
                        candidate_a, candidate_b);
                 let candidates_same = match (&candidate_a.origin,
                                              &candidate_b.origin) {
@@ -936,7 +936,7 @@ impl<'self> LookupContext<'self> {
         let tcx = self.tcx();
         let fty = ty::mk_bare_fn(tcx, candidate.method_ty.fty.clone());
 
-        debug!("confirm_candidate(expr=%s, candidate=%s, fty=%s)",
+        debug2!("confirm_candidate(expr={}, candidate={}, fty={})",
                self.expr.repr(tcx),
                self.cand_to_str(candidate),
                self.ty_to_str(fty));
@@ -992,11 +992,11 @@ impl<'self> LookupContext<'self> {
         };
 
         // Compute the method type with type parameters substituted
-        debug!("fty=%s all_substs=%s",
+        debug2!("fty={} all_substs={}",
                self.ty_to_str(fty),
                ty::substs_to_str(tcx, &all_substs));
         let fty = ty::subst(tcx, &all_substs, fty);
-        debug!("after subst, fty=%s", self.ty_to_str(fty));
+        debug2!("after subst, fty={}", self.ty_to_str(fty));
 
         // Replace any bound regions that appear in the function
         // signature with region variables
@@ -1005,7 +1005,7 @@ impl<'self> LookupContext<'self> {
             ref s => {
                 tcx.sess.span_bug(
                     self.expr.span,
-                    fmt!("Invoking method with non-bare-fn ty: %?", s));
+                    format!("Invoking method with non-bare-fn ty: {:?}", s));
             }
         };
         let (_, opt_transformed_self_ty, fn_sig) =
@@ -1019,7 +1019,7 @@ impl<'self> LookupContext<'self> {
             purity: bare_fn_ty.purity,
             abis: bare_fn_ty.abis.clone(),
         });
-        debug!("after replacing bound regions, fty=%s", self.ty_to_str(fty));
+        debug2!("after replacing bound regions, fty={}", self.ty_to_str(fty));
 
         let self_mode = get_mode_from_explicit_self(candidate.method_ty.explicit_self);
 
@@ -1032,7 +1032,7 @@ impl<'self> LookupContext<'self> {
                                 rcvr_ty, transformed_self_ty) {
             result::Ok(_) => (),
             result::Err(_) => {
-                self.bug(fmt!("%s was a subtype of %s but now is not?",
+                self.bug(format!("{} was a subtype of {} but now is not?",
                               self.ty_to_str(rcvr_ty),
                               self.ty_to_str(transformed_self_ty)));
             }
@@ -1106,7 +1106,7 @@ impl<'self> LookupContext<'self> {
                     }
                     _ => {
                         self.bug(
-                            fmt!("'impossible' transformed_self_ty: %s",
+                            format!("'impossible' transformed_self_ty: {}",
                                  transformed_self_ty.repr(self.tcx())));
                     }
                 }
@@ -1189,12 +1189,12 @@ impl<'self> LookupContext<'self> {
     // `rcvr_ty` is the type of the expression. It may be a subtype of a
     // candidate method's `self_ty`.
     fn is_relevant(&self, rcvr_ty: ty::t, candidate: &Candidate) -> bool {
-        debug!("is_relevant(rcvr_ty=%s, candidate=%s)",
+        debug2!("is_relevant(rcvr_ty={}, candidate={})",
                self.ty_to_str(rcvr_ty), self.cand_to_str(candidate));
 
         return match candidate.method_ty.explicit_self {
             sty_static => {
-                debug!("(is relevant?) explicit self is static");
+                debug2!("(is relevant?) explicit self is static");
                 false
             }
 
@@ -1203,7 +1203,7 @@ impl<'self> LookupContext<'self> {
             }
 
             sty_region(_, m) => {
-                debug!("(is relevant?) explicit self is a region");
+                debug2!("(is relevant?) explicit self is a region");
                 match ty::get(rcvr_ty).sty {
                     ty::ty_rptr(_, mt) => {
                         mutability_matches(mt.mutbl, m) &&
@@ -1220,7 +1220,7 @@ impl<'self> LookupContext<'self> {
             }
 
             sty_box(m) => {
-                debug!("(is relevant?) explicit self is a box");
+                debug2!("(is relevant?) explicit self is a box");
                 match ty::get(rcvr_ty).sty {
                     ty::ty_box(mt) => {
                         mutability_matches(mt.mutbl, m) &&
@@ -1237,7 +1237,7 @@ impl<'self> LookupContext<'self> {
             }
 
             sty_uniq => {
-                debug!("(is relevant?) explicit self is a unique pointer");
+                debug2!("(is relevant?) explicit self is a unique pointer");
                 match ty::get(rcvr_ty).sty {
                     ty::ty_uniq(mt) => {
                         rcvr_matches_ty(self.fcx, mt.ty, candidate)
@@ -1303,14 +1303,14 @@ impl<'self> LookupContext<'self> {
         let span = if did.crate == ast::LOCAL_CRATE {
             match self.tcx().items.find(&did.node) {
               Some(&ast_map::node_method(m, _, _)) => m.span,
-              _ => fail!("report_static_candidate: bad item %?", did)
+              _ => fail2!("report_static_candidate: bad item {:?}", did)
             }
         } else {
             self.expr.span
         };
         self.tcx().sess.span_note(
             span,
-            fmt!("candidate #%u is `%s`",
+            format!("candidate \\#{} is `{}`",
                  (idx+1u),
                  ty::item_path_str(self.tcx(), did)));
     }
@@ -1318,7 +1318,7 @@ impl<'self> LookupContext<'self> {
     fn report_param_candidate(&self, idx: uint, did: DefId) {
         self.tcx().sess.span_note(
             self.expr.span,
-            fmt!("candidate #%u derives from the bound `%s`",
+            format!("candidate \\#{} derives from the bound `{}`",
                  (idx+1u),
                  ty::item_path_str(self.tcx(), did)));
     }
@@ -1326,8 +1326,8 @@ impl<'self> LookupContext<'self> {
     fn report_trait_candidate(&self, idx: uint, did: DefId) {
         self.tcx().sess.span_note(
             self.expr.span,
-            fmt!("candidate #%u derives from the type of the receiver, \
-                  which is the trait `%s`",
+            format!("candidate \\#{} derives from the type of the receiver, \
+                  which is the trait `{}`",
                  (idx+1u),
                  ty::item_path_str(self.tcx(), did)));
     }
@@ -1345,7 +1345,7 @@ impl<'self> LookupContext<'self> {
     }
 
     fn cand_to_str(&self, cand: &Candidate) -> ~str {
-        fmt!("Candidate(rcvr_ty=%s, rcvr_substs=%s, origin=%?)",
+        format!("Candidate(rcvr_ty={}, rcvr_substs={}, origin={:?})",
              cand.rcvr_match_condition.repr(self.tcx()),
              ty::substs_to_str(self.tcx(), &cand.rcvr_substs),
              cand.origin)
@@ -1371,10 +1371,10 @@ impl Repr for RcvrMatchCondition {
     fn repr(&self, tcx: ty::ctxt) -> ~str {
         match *self {
             RcvrMatchesIfObject(d) => {
-                fmt!("RcvrMatchesIfObject(%s)", d.repr(tcx))
+                format!("RcvrMatchesIfObject({})", d.repr(tcx))
             }
             RcvrMatchesIfSubtype(t) => {
-                fmt!("RcvrMatchesIfSubtype(%s)", t.repr(tcx))
+                format!("RcvrMatchesIfSubtype({})", t.repr(tcx))
             }
         }
     }
diff --git a/src/librustc/middle/typeck/check/mod.rs b/src/librustc/middle/typeck/check/mod.rs
index b689090d3fd..54de7fc1bab 100644
--- a/src/librustc/middle/typeck/check/mod.rs
+++ b/src/librustc/middle/typeck/check/mod.rs
@@ -110,7 +110,6 @@ use util::ppaux::{bound_region_ptr_to_str};
 use util::ppaux;
 
 
-use std::cast::transmute;
 use std::hashmap::HashMap;
 use std::result;
 use std::util::replace;
@@ -363,7 +362,7 @@ impl Visitor<()> for GatherLocalsVisitor {
               _ => Some(self.fcx.to_ty(&local.ty))
             };
             self.assign(local.id, o_ty);
-            debug!("Local variable %s is assigned type %s",
+            debug2!("Local variable {} is assigned type {}",
                    self.fcx.pat_to_str(local.pat),
                    self.fcx.infcx().ty_to_str(
                        self.fcx.inh.locals.get_copy(&local.id)));
@@ -376,7 +375,7 @@ impl Visitor<()> for GatherLocalsVisitor {
               ast::PatIdent(_, ref path, _)
                   if pat_util::pat_is_binding(self.fcx.ccx.tcx.def_map, p) => {
                 self.assign(p.id, None);
-                debug!("Pattern binding %s is assigned to %s",
+                debug2!("Pattern binding {} is assigned to {}",
                        self.tcx.sess.str_of(path.segments[0].identifier),
                        self.fcx.infcx().ty_to_str(
                            self.fcx.inh.locals.get_copy(&p.id)));
@@ -451,7 +450,7 @@ pub fn check_fn(ccx: @mut CrateCtxt,
     let arg_tys = fn_sig.inputs.map(|a| *a);
     let ret_ty = fn_sig.output;
 
-    debug!("check_fn(arg_tys=%?, ret_ty=%?, opt_self_ty=%?)",
+    debug2!("check_fn(arg_tys={:?}, ret_ty={:?}, opt_self_ty={:?})",
            arg_tys.map(|&a| ppaux::ty_to_str(tcx, a)),
            ppaux::ty_to_str(tcx, ret_ty),
            opt_self_info.map(|si| ppaux::ty_to_str(tcx, si.self_ty)));
@@ -511,7 +510,7 @@ pub fn check_fn(ccx: @mut CrateCtxt,
         // Add the self parameter
         for self_info in opt_self_info.iter() {
             visit.assign(self_info.self_id, Some(self_info.self_ty));
-            debug!("self is assigned to %s",
+            debug2!("self is assigned to {}",
                    fcx.infcx().ty_to_str(
                        fcx.inh.locals.get_copy(&self_info.self_id)));
         }
@@ -565,7 +564,7 @@ pub fn check_no_duplicate_fields(tcx: ty::ctxt,
         let orig_sp = field_names.find(&id).map_move(|x| *x);
         match orig_sp {
             Some(orig_sp) => {
-                tcx.sess.span_err(sp, fmt!("Duplicate field name %s in record type declaration",
+                tcx.sess.span_err(sp, format!("Duplicate field name {} in record type declaration",
                                            tcx.sess.str_of(id)));
                 tcx.sess.span_note(orig_sp, "First declaration of this field occurred here");
                 break;
@@ -589,7 +588,7 @@ pub fn check_struct(ccx: @mut CrateCtxt, id: ast::NodeId, span: Span) {
 }
 
 pub fn check_item(ccx: @mut CrateCtxt, it: @ast::item) {
-    debug!("check_item(it.id=%d, it.ident=%s)",
+    debug2!("check_item(it.id={}, it.ident={})",
            it.id,
            ty::item_path_str(ccx.tcx, local_def(it.id)));
     let _indenter = indenter();
@@ -607,7 +606,7 @@ pub fn check_item(ccx: @mut CrateCtxt, it: @ast::item) {
       }
       ast::item_impl(_, _, _, ref ms) => {
         let rp = ccx.tcx.region_paramd_items.find(&it.id).map_move(|x| *x);
-        debug!("item_impl %s with id %d rp %?",
+        debug2!("item_impl {} with id {} rp {:?}",
                ccx.tcx.sess.str_of(it.ident), it.id, rp);
         for m in ms.iter() {
             check_method(ccx, *m);
@@ -645,7 +644,7 @@ pub fn check_item(ccx: @mut CrateCtxt, it: @ast::item) {
                 if tpt.generics.has_type_params() {
                     ccx.tcx.sess.span_err(
                         item.span,
-                        fmt!("foreign items may not have type parameters"));
+                        format!("foreign items may not have type parameters"));
                 }
             }
         }
@@ -691,7 +690,7 @@ impl FnCtxt {
                 } else {
                     result::Err(RegionError {
                         msg: {
-                            fmt!("named region `%s` not in scope here",
+                            format!("named region `{}` not in scope here",
                                  bound_region_ptr_to_str(self.tcx(), br))
                         },
                         replacement: {
@@ -722,7 +721,7 @@ impl RegionScope for FnCtxt {
 impl FnCtxt {
     pub fn tag(&self) -> ~str {
         unsafe {
-            fmt!("%x", transmute(self))
+            format!("{}", self as *FnCtxt)
         }
     }
 
@@ -732,7 +731,7 @@ impl FnCtxt {
             None => {
                 self.tcx().sess.span_bug(
                     span,
-                    fmt!("No type for local variable %?", nid));
+                    format!("No type for local variable {:?}", nid));
             }
         }
     }
@@ -743,14 +742,14 @@ impl FnCtxt {
 
     #[inline]
     pub fn write_ty(&self, node_id: ast::NodeId, ty: ty::t) {
-        debug!("write_ty(%d, %s) in fcx %s",
+        debug2!("write_ty({}, {}) in fcx {}",
                node_id, ppaux::ty_to_str(self.tcx(), ty), self.tag());
         self.inh.node_types.insert(node_id, ty);
     }
 
     pub fn write_substs(&self, node_id: ast::NodeId, substs: ty::substs) {
         if !ty::substs_is_noop(&substs) {
-            debug!("write_substs(%d, %s) in fcx %s",
+            debug2!("write_substs({}, {}) in fcx {}",
                    node_id,
                    ty::substs_to_str(self.tcx(), &substs),
                    self.tag());
@@ -782,7 +781,7 @@ impl FnCtxt {
     pub fn write_adjustment(&self,
                             node_id: ast::NodeId,
                             adj: @ty::AutoAdjustment) {
-        debug!("write_adjustment(node_id=%?, adj=%?)", node_id, adj);
+        debug2!("write_adjustment(node_id={:?}, adj={:?})", node_id, adj);
         self.inh.adjustments.insert(node_id, adj);
     }
 
@@ -808,7 +807,7 @@ impl FnCtxt {
         match self.inh.node_types.find(&ex.id) {
             Some(&t) => t,
             None => {
-                self.tcx().sess.bug(fmt!("no type for expr in fcx %s",
+                self.tcx().sess.bug(format!("no type for expr in fcx {}",
                                          self.tag()));
             }
         }
@@ -819,7 +818,7 @@ impl FnCtxt {
             Some(&t) => t,
             None => {
                 self.tcx().sess.bug(
-                    fmt!("no type for node %d: %s in fcx %s",
+                    format!("no type for node {}: {} in fcx {}",
                          id, ast_map::node_id_to_str(
                              self.tcx().items, id,
                              token::get_ident_interner()),
@@ -833,7 +832,7 @@ impl FnCtxt {
             Some(ts) => (*ts).clone(),
             None => {
                 self.tcx().sess.bug(
-                    fmt!("no type substs for node %d: %s in fcx %s",
+                    format!("no type substs for node {}: {} in fcx {}",
                          id, ast_map::node_id_to_str(
                              self.tcx().items, id,
                              token::get_ident_interner()),
@@ -1212,7 +1211,7 @@ fn check_type_parameter_positions_in_path(function_context: @mut FnCtxt,
                     function_context.tcx()
                                     .sess
                                     .span_err(path.span,
-                                              fmt!("this %s has a lifetime \
+                                              format!("this {} has a lifetime \
                                                     parameter but no \
                                                     lifetime was specified",
                                                    name))
@@ -1221,7 +1220,7 @@ fn check_type_parameter_positions_in_path(function_context: @mut FnCtxt,
                     function_context.tcx()
                                     .sess
                                     .span_err(path.span,
-                                              fmt!("this %s has no lifetime \
+                                              format!("this {} has no lifetime \
                                                     parameter but a lifetime \
                                                     was specified",
                                                    name))
@@ -1249,10 +1248,10 @@ fn check_type_parameter_positions_in_path(function_context: @mut FnCtxt,
                 function_context.tcx()
                                 .sess
                                 .span_err(path.span,
-                                          fmt!("the %s referenced by this \
-                                                path has %u type \
-                                                parameter%s, but %u type \
-                                                parameter%s were supplied",
+                                          format!("the {} referenced by this \
+                                                path has {} type \
+                                                parameter{}, but {} type \
+                                                parameter{} were supplied",
                                                name,
                                                trait_type_parameter_count,
                                                trait_count_suffix,
@@ -1283,7 +1282,7 @@ fn check_type_parameter_positions_in_path(function_context: @mut FnCtxt,
                 function_context.tcx()
                                 .sess
                                 .span_note(typ.span,
-                                           fmt!("this is a %?", def));
+                                           format!("this is a {:?}", def));
             }
         }
     }
@@ -1303,7 +1302,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                                expr: @ast::Expr,
                                expected: Option<ty::t>,
                                unifier: &fn()) {
-    debug!(">> typechecking");
+    debug2!(">> typechecking");
 
     fn check_method_argument_types(
         fcx: @mut FnCtxt,
@@ -1329,7 +1328,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                 _ => {
                     fcx.tcx().sess.span_bug(
                         sp,
-                        fmt!("Method without bare fn type"));
+                        format!("Method without bare fn type"));
                 }
             }
         }
@@ -1366,8 +1365,8 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                 ast::ForSugar => " (including the closure passed by \
                                   the `for` keyword)"
             };
-            let msg = fmt!("this function takes %u parameter%s but \
-                            %u parameter%s supplied%s",
+            let msg = format!("this function takes {} parameter{} but \
+                            {} parameter{} supplied{}",
                            expected_arg_count,
                            if expected_arg_count == 1 {""}
                            else {"s"},
@@ -1381,7 +1380,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
             vec::from_elem(supplied_arg_count, ty::mk_err())
         };
 
-        debug!("check_argument_types: formal_tys=%?",
+        debug2!("check_argument_types: formal_tys={:?}",
                formal_tys.map(|t| fcx.infcx().ty_to_str(*t)));
 
         // Check the arguments.
@@ -1393,7 +1392,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
         let xs = [false, true];
         for check_blocks in xs.iter() {
             let check_blocks = *check_blocks;
-            debug!("check_blocks=%b", check_blocks);
+            debug2!("check_blocks={}", check_blocks);
 
             // More awful hacks: before we check the blocks, try to do
             // an "opportunistic" vtable resolution of any trait
@@ -1410,7 +1409,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                 };
 
                 if is_block == check_blocks {
-                    debug!("checking the argument");
+                    debug2!("checking the argument");
                     let mut formal_ty = formal_tys[i];
 
                     match deref_args {
@@ -1459,8 +1458,8 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                 match ty::get(output).sty {
                     ty::ty_bool => {}
                     _ => fcx.type_error_message(call_expr.span, |actual| {
-                            fmt!("expected `for` closure to return `bool`, \
-                                  but found `%s`", actual) },
+                            format!("expected `for` closure to return `bool`, \
+                                  but found `{}`", actual) },
                             output, None)
                 }
                 ty::mk_nil()
@@ -1508,8 +1507,8 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
             ty::ty_closure(ty::ClosureTy {sig: ref sig, _}) => sig,
             _ => {
                 fcx.type_error_message(call_expr.span, |actual| {
-                    fmt!("expected function but \
-                          found `%s`", actual) }, fn_ty, None);
+                    format!("expected function but \
+                          found `{}`", actual) }, fn_ty, None);
                 &error_fn_sig
             }
         };
@@ -1564,12 +1563,12 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                 method_map.insert(expr.id, (*entry));
             }
             None => {
-                debug!("(checking method call) failing expr is %d", expr.id);
+                debug2!("(checking method call) failing expr is {}", expr.id);
 
                 fcx.type_error_message(expr.span,
                   |actual| {
-                      fmt!("type `%s` does not implement any method in scope \
-                            named `%s`",
+                      format!("type `{}` does not implement any method in scope \
+                            named `{}`",
                            actual,
                            fcx.ccx.tcx.sess.str_of(method_name))
                   },
@@ -1721,8 +1720,8 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
             fcx.write_error(expr.id);
             fcx.write_error(rhs.id);
             fcx.type_error_message(expr.span, |actual| {
-                fmt!("binary operation %s cannot be applied \
-                      to type `%s`",
+                format!("binary operation {} cannot be applied \
+                      to type `{}`",
                      ast_util::binop_to_str(op), actual)},
                                    lhs_t, None)
 
@@ -1742,8 +1741,8 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
         } else {
             fcx.type_error_message(expr.span,
                                    |actual| {
-                                        fmt!("binary operation %s cannot be \
-                                              applied to type `%s`",
+                                        format!("binary operation {} cannot be \
+                                              applied to type `{}`",
                                              ast_util::binop_to_str(op),
                                              actual)
                                    },
@@ -1771,8 +1770,8 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
             Some(ref name) => {
                 let if_op_unbound = || {
                     fcx.type_error_message(ex.span, |actual| {
-                        fmt!("binary operation %s cannot be applied \
-                              to type `%s`",
+                        format!("binary operation {} cannot be applied \
+                              to type `{}`",
                              ast_util::binop_to_str(op), actual)},
                             lhs_resolved_t, None)
                 };
@@ -1815,7 +1814,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
             DoDerefArgs, DontAutoderefReceiver,
             || {
                 fcx.type_error_message(ex.span, |actual| {
-                    fmt!("cannot apply unary operator `%s` to type `%s`",
+                    format!("cannot apply unary operator `{}` to type `{}`",
                          op_str, actual)
                 }, rhs_t, None);
             }, expected_t)
@@ -1918,7 +1917,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
             ty::mk_closure(tcx, fn_ty_copy)
         };
 
-        debug!("check_expr_fn_with_unifier fty=%s",
+        debug2!("check_expr_fn_with_unifier fty={}",
                fcx.infcx().ty_to_str(fty));
 
         fcx.write_ty(expr.id, fty);
@@ -1952,7 +1951,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
 
                 // (1) verify that the class id actually has a field called
                 // field
-                debug!("class named %s", ppaux::ty_to_str(tcx, base_t));
+                debug2!("class named {}", ppaux::ty_to_str(tcx, base_t));
                 let cls_items = ty::lookup_struct_fields(tcx, base_id);
                 match lookup_field_ty(tcx, base_id, cls_items,
                                       field, &(*substs)) {
@@ -1983,7 +1982,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                 fcx.type_error_message(
                     expr.span,
                     |actual| {
-                        fmt!("attempted to take value of method `%s` on type `%s` \
+                        format!("attempted to take value of method `{}` on type `{}` \
                               (try writing an anonymous function)",
                              token::interner_get(field), actual)
                     },
@@ -1994,7 +1993,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                 fcx.type_error_message(
                     expr.span,
                     |actual| {
-                        fmt!("attempted access of field `%s` on type `%s`, \
+                        format!("attempted access of field `{}` on type `{}`, \
                               but no field with that name was found",
                              token::interner_get(field), actual)
                     },
@@ -2032,14 +2031,14 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                 None => {
                     tcx.sess.span_err(
                         field.span,
-                        fmt!("structure has no field named `%s`",
+                        format!("structure has no field named `{}`",
                              tcx.sess.str_of(field.ident)));
                     error_happened = true;
                 }
                 Some((_, true)) => {
                     tcx.sess.span_err(
                         field.span,
-                        fmt!("field `%s` specified more than once",
+                        format!("field `{}` specified more than once",
                              tcx.sess.str_of(field.ident)));
                     error_happened = true;
                 }
@@ -2079,7 +2078,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                 }
 
                 tcx.sess.span_err(span,
-                                  fmt!("missing field%s: %s",
+                                  format!("missing field{}: {}",
                                        if missing_fields.len() == 1 {
                                            ""
                                        } else {
@@ -2419,7 +2418,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                                 _ => {
                                     fcx.type_error_message(expr.span,
                                         |actual| {
-                                            fmt!("type %s cannot be dereferenced", actual)
+                                            format!("type {} cannot be dereferenced", actual)
                                     }, oprnd_t, None);
                                 }
                             }
@@ -2567,7 +2566,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
         }
       }
       ast::ExprForLoop(*) =>
-          fail!("non-desugared expr_for_loop"),
+          fail2!("non-desugared expr_for_loop"),
       ast::ExprLoop(ref body, _) => {
         check_block_no_value(fcx, (body));
         if !may_break(tcx, expr.id, body) {
@@ -2593,8 +2592,8 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
             _ => match expected {
                 Some(expected_t) => {
                     fcx.type_error_message(expr.span, |actual| {
-                        fmt!("last argument in `do` call \
-                              has non-closure type: %s",
+                        format!("last argument in `do` call \
+                              has non-closure type: {}",
                              actual)
                     }, expected_t, None);
                     let err_ty = ty::mk_err();
@@ -2615,7 +2614,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
             demand::suptype(fcx, b.span, inner_ty, fcx.expr_ty(b));
           }
           // argh
-          _ => fail!("expected fn ty")
+          _ => fail2!("expected fn ty")
         }
         fcx.write_ty(expr.id, fcx.node_ty(b.id));
       }
@@ -2659,8 +2658,8 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
         let t_1 = fcx.to_ty(t);
         let t_e = fcx.expr_ty(e);
 
-        debug!("t_1=%s", fcx.infcx().ty_to_str(t_1));
-        debug!("t_e=%s", fcx.infcx().ty_to_str(t_e));
+        debug2!("t_1={}", fcx.infcx().ty_to_str(t_1));
+        debug2!("t_e={}", fcx.infcx().ty_to_str(t_e));
 
         if ty::type_is_error(t_e) {
             fcx.write_error(id);
@@ -2676,12 +2675,12 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                 _ => {
                     if ty::type_is_nil(t_e) {
                         fcx.type_error_message(expr.span, |actual| {
-                            fmt!("cast from nil: `%s` as `%s`", actual,
+                            format!("cast from nil: `{}` as `{}`", actual,
                                  fcx.infcx().ty_to_str(t_1))
                         }, t_e, None);
                     } else if ty::type_is_nil(t_1) {
                         fcx.type_error_message(expr.span, |actual| {
-                            fmt!("cast to nil: `%s` as `%s`", actual,
+                            format!("cast to nil: `{}` as `{}`", actual,
                                  fcx.infcx().ty_to_str(t_1))
                         }, t_e, None);
                     }
@@ -2698,7 +2697,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                     } else if t_1_is_char {
                         if ty::get(te).sty != ty::ty_uint(ast::ty_u8) {
                             fcx.type_error_message(expr.span, |actual| {
-                                fmt!("only `u8` can be cast as `char`, not `%s`", actual)
+                                format!("only `u8` can be cast as `char`, not `{}`", actual)
                             }, t_e, None);
                         }
                     } else if ty::get(t1).sty == ty::ty_bool {
@@ -2752,7 +2751,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                         record the issue number in this comment.
                         */
                         fcx.type_error_message(expr.span, |actual| {
-                            fmt!("non-scalar cast: `%s` as `%s`", actual,
+                            format!("non-scalar cast: `{}` as `{}`", actual,
                                  fcx.infcx().ty_to_str(t_1))
                         }, t_e, None);
                     }
@@ -2864,8 +2863,8 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
                       let error_message = || {
                         fcx.type_error_message(expr.span,
                                                |actual| {
-                                                fmt!("cannot index a value \
-                                                      of type `%s`",
+                                                format!("cannot index a value \
+                                                      of type `{}`",
                                                      actual)
                                                },
                                                base_t,
@@ -2889,9 +2888,9 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
        }
     }
 
-    debug!("type of expr(%d) %s is...", expr.id,
+    debug2!("type of expr({}) {} is...", expr.id,
            syntax::print::pprust::expr_to_str(expr, tcx.sess.intr()));
-    debug!("... %s, expected is %s",
+    debug2!("... {}, expected is {}",
            ppaux::ty_to_str(tcx, fcx.expr_ty(expr)),
            match expected {
                Some(t) => ppaux::ty_to_str(tcx, t),
@@ -2904,7 +2903,7 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
 pub fn require_integral(fcx: @mut FnCtxt, sp: Span, t: ty::t) {
     if !type_is_integral(fcx, sp, t) {
         fcx.type_error_message(sp, |actual| {
-            fmt!("mismatched types: expected integral type but found `%s`",
+            format!("mismatched types: expected integral type but found `{}`",
                  actual)
         }, t, None);
     }
@@ -3110,9 +3109,9 @@ pub fn check_instantiable(tcx: ty::ctxt,
                           item_id: ast::NodeId) {
     let item_ty = ty::node_id_to_type(tcx, item_id);
     if !ty::is_instantiable(tcx, item_ty) {
-        tcx.sess.span_err(sp, fmt!("this type cannot be instantiated \
+        tcx.sess.span_err(sp, format!("this type cannot be instantiated \
                   without an instance of itself; \
-                  consider using `Option<%s>`",
+                  consider using `Option<{}>`",
                                    ppaux::ty_to_str(tcx, item_ty)));
     }
 }
@@ -3171,7 +3170,7 @@ pub fn check_enum_variants(ccx: @mut CrateCtxt,
 
             match v.node.disr_expr {
                 Some(e) => {
-                    debug!("disr expr, checking %s", pprust::expr_to_str(e, ccx.tcx.sess.intr()));
+                    debug2!("disr expr, checking {}", pprust::expr_to_str(e, ccx.tcx.sess.intr()));
 
                     let fcx = blank_fn_ctxt(ccx, rty, e.id);
                     let declty = ty::mk_int_var(ccx.tcx, fcx.infcx().next_int_var_id());
@@ -3187,7 +3186,7 @@ pub fn check_enum_variants(ccx: @mut CrateCtxt,
                             ccx.tcx.sess.span_err(e.span, "expected signed integer constant");
                         }
                         Err(ref err) => {
-                            ccx.tcx.sess.span_err(e.span, fmt!("expected constant: %s", (*err)));
+                            ccx.tcx.sess.span_err(e.span, format!("expected constant: {}", (*err)));
                         }
                     }
                 },
@@ -3301,7 +3300,7 @@ pub fn instantiate_path(fcx: @mut FnCtxt,
                         def: ast::Def,
                         span: Span,
                         node_id: ast::NodeId) {
-    debug!(">>> instantiate_path");
+    debug2!(">>> instantiate_path");
 
     let ty_param_count = tpt.generics.type_param_defs.len();
     let mut ty_substs_len = 0;
@@ -3309,7 +3308,7 @@ pub fn instantiate_path(fcx: @mut FnCtxt,
         ty_substs_len += segment.types.len()
     }
 
-    debug!("tpt=%s ty_param_count=%? ty_substs_len=%?",
+    debug2!("tpt={} ty_param_count={:?} ty_substs_len={:?}",
            tpt.repr(fcx.tcx()),
            ty_param_count,
            ty_substs_len);
@@ -3364,13 +3363,13 @@ pub fn instantiate_path(fcx: @mut FnCtxt,
     } else if ty_substs_len > user_type_parameter_count {
         fcx.ccx.tcx.sess.span_err
             (span,
-             fmt!("too many type parameters provided: expected %u, found %u",
+             format!("too many type parameters provided: expected {}, found {}",
                   user_type_parameter_count, ty_substs_len));
         fcx.infcx().next_ty_vars(ty_param_count)
     } else if ty_substs_len < user_type_parameter_count {
         fcx.ccx.tcx.sess.span_err
             (span,
-             fmt!("not enough type parameters provided: expected %u, found %u",
+             format!("not enough type parameters provided: expected {}, found {}",
                   user_type_parameter_count, ty_substs_len));
         fcx.infcx().next_ty_vars(ty_param_count)
     } else {
@@ -3408,7 +3407,7 @@ pub fn instantiate_path(fcx: @mut FnCtxt,
     };
     fcx.write_ty_substs(node_id, tpt.ty, substs);
 
-    debug!("<<<");
+    debug2!("<<<");
 }
 
 // Resolves `typ` by a single level if `typ` is a type variable.  If no
@@ -3504,7 +3503,7 @@ pub fn check_bounds_are_used(ccx: @mut CrateCtxt,
                              span: Span,
                              tps: &OptVec<ast::TyParam>,
                              ty: ty::t) {
-    debug!("check_bounds_are_used(n_tps=%u, ty=%s)",
+    debug2!("check_bounds_are_used(n_tps={}, ty={})",
            tps.len(), ppaux::ty_to_str(ccx.tcx, ty));
 
     // make a vector of booleans initially false, set to true when used
@@ -3517,7 +3516,7 @@ pub fn check_bounds_are_used(ccx: @mut CrateCtxt,
         |t| {
             match ty::get(t).sty {
               ty::ty_param(param_ty {idx, _}) => {
-                  debug!("Found use of ty param #%u", idx);
+                  debug2!("Found use of ty param \\#{}", idx);
                   tps_used[idx] = true;
               }
               _ => ()
@@ -3528,7 +3527,7 @@ pub fn check_bounds_are_used(ccx: @mut CrateCtxt,
     for (i, b) in tps_used.iter().enumerate() {
         if !*b {
             ccx.tcx.sess.span_err(
-                span, fmt!("type parameter `%s` is unused",
+                span, format!("type parameter `{}` is unused",
                            ccx.tcx.sess.str_of(tps.get(i).ident)));
         }
     }
@@ -3577,7 +3576,7 @@ pub fn check_intrinsic_type(ccx: @mut CrateCtxt, it: @ast::foreign_item) {
             }
             op => {
                 tcx.sess.span_err(it.span,
-                                  fmt!("unrecognized atomic operation function: `%s`",
+                                  format!("unrecognized atomic operation function: `{}`",
                                        op));
                 return;
             }
@@ -3860,7 +3859,7 @@ pub fn check_intrinsic_type(ccx: @mut CrateCtxt, it: @ast::foreign_item) {
 
             ref other => {
                 tcx.sess.span_err(it.span,
-                                  fmt!("unrecognized intrinsic function: `%s`",
+                                  format!("unrecognized intrinsic function: `{}`",
                                        *other));
                 return;
             }
@@ -3876,14 +3875,14 @@ pub fn check_intrinsic_type(ccx: @mut CrateCtxt, it: @ast::foreign_item) {
     let i_ty = ty::lookup_item_type(ccx.tcx, local_def(it.id));
     let i_n_tps = i_ty.generics.type_param_defs.len();
     if i_n_tps != n_tps {
-        tcx.sess.span_err(it.span, fmt!("intrinsic has wrong number \
-                                         of type parameters: found %u, \
-                                         expected %u", i_n_tps, n_tps));
+        tcx.sess.span_err(it.span, format!("intrinsic has wrong number \
+                                         of type parameters: found {}, \
+                                         expected {}", i_n_tps, n_tps));
     } else {
         require_same_types(
             tcx, None, false, it.span, i_ty.ty, fty,
-            || fmt!("intrinsic has wrong type: \
-                      expected `%s`",
+            || format!("intrinsic has wrong type: \
+                      expected `{}`",
                      ppaux::ty_to_str(ccx.tcx, fty)));
     }
 }
diff --git a/src/librustc/middle/typeck/check/regionck.rs b/src/librustc/middle/typeck/check/regionck.rs
index 78c20b54845..edc2947d890 100644
--- a/src/librustc/middle/typeck/check/regionck.rs
+++ b/src/librustc/middle/typeck/check/regionck.rs
@@ -68,7 +68,7 @@ fn encl_region_of_def(fcx: @mut FnCtxt, def: ast::Def) -> ty::Region {
             }
         }
         _ => {
-            tcx.sess.bug(fmt!("unexpected def in encl_region_of_def: %?",
+            tcx.sess.bug(format!("unexpected def in encl_region_of_def: {:?}",
                               def))
         }
     }
@@ -211,7 +211,7 @@ fn visit_local(rcx: &mut Rcx, l: @ast::Local) {
 
 fn constrain_bindings_in_pat(pat: @ast::Pat, rcx: &mut Rcx) {
     let tcx = rcx.fcx.tcx();
-    debug!("regionck::visit_pat(pat=%s)", pat.repr(tcx));
+    debug2!("regionck::visit_pat(pat={})", pat.repr(tcx));
     do pat_util::pat_bindings(tcx.def_map, pat) |_, id, span, _| {
         // If we have a variable that contains region'd data, that
         // data will be accessible from anywhere that the variable is
@@ -244,7 +244,7 @@ fn constrain_bindings_in_pat(pat: @ast::Pat, rcx: &mut Rcx) {
 }
 
 fn visit_expr(rcx: &mut Rcx, expr: @ast::Expr) {
-    debug!("regionck::visit_expr(e=%s, repeating_scope=%?)",
+    debug2!("regionck::visit_expr(e={}, repeating_scope={:?})",
            expr.repr(rcx.fcx.tcx()), rcx.repeating_scope);
 
     let has_method_map = rcx.fcx.inh.method_map.contains_key(&expr.id);
@@ -302,7 +302,7 @@ fn visit_expr(rcx: &mut Rcx, expr: @ast::Expr) {
     {
         let r = rcx.fcx.inh.adjustments.find(&expr.id);
         for &adjustment in r.iter() {
-            debug!("adjustment=%?", adjustment);
+            debug2!("adjustment={:?}", adjustment);
             match *adjustment {
                 @ty::AutoDerefRef(
                     ty::AutoDerefRef {autoderefs: autoderefs, autoref: opt_autoref}) =>
@@ -515,7 +515,7 @@ fn constrain_callee(rcx: &mut Rcx,
             //
             // tcx.sess.span_bug(
             //     callee_expr.span,
-            //     fmt!("Calling non-function: %s", callee_ty.repr(tcx)));
+            //     format!("Calling non-function: {}", callee_ty.repr(tcx)));
         }
     }
 }
@@ -535,7 +535,7 @@ fn constrain_call(rcx: &mut Rcx,
     //! appear in the arguments appropriately.
 
     let tcx = rcx.fcx.tcx();
-    debug!("constrain_call(call_expr=%s, implicitly_ref_args=%?)",
+    debug2!("constrain_call(call_expr={}, implicitly_ref_args={:?})",
            call_expr.repr(tcx), implicitly_ref_args);
     let callee_ty = rcx.resolve_node_type(callee_id);
     if ty::type_is_error(callee_ty) {
@@ -597,7 +597,7 @@ fn constrain_derefs(rcx: &mut Rcx,
     let tcx = rcx.fcx.tcx();
     let r_deref_expr = ty::re_scope(deref_expr.id);
     for i in range(0u, derefs) {
-        debug!("constrain_derefs(deref_expr=?, derefd_ty=%s, derefs=%?/%?",
+        debug2!("constrain_derefs(deref_expr=?, derefd_ty={}, derefs={:?}/{:?}",
                rcx.fcx.infcx().ty_to_str(derefd_ty),
                i, derefs);
 
@@ -638,7 +638,7 @@ fn constrain_index(rcx: &mut Rcx,
      * includes the deref expr.
      */
 
-    debug!("constrain_index(index_expr=?, indexed_ty=%s",
+    debug2!("constrain_index(index_expr=?, indexed_ty={}",
            rcx.fcx.infcx().ty_to_str(indexed_ty));
 
     let r_index_expr = ty::re_scope(index_expr.id);
@@ -662,13 +662,13 @@ fn constrain_free_variables(rcx: &mut Rcx,
      */
 
     let tcx = rcx.fcx.ccx.tcx;
-    debug!("constrain_free_variables(%s, %s)",
+    debug2!("constrain_free_variables({}, {})",
            region.repr(tcx), expr.repr(tcx));
     for freevar in get_freevars(tcx, expr.id).iter() {
-        debug!("freevar def is %?", freevar.def);
+        debug2!("freevar def is {:?}", freevar.def);
         let def = freevar.def;
         let en_region = encl_region_of_def(rcx.fcx, def);
-        debug!("en_region = %s", en_region.repr(tcx));
+        debug2!("en_region = {}", en_region.repr(tcx));
         rcx.fcx.mk_subr(true, infer::FreeVariable(freevar.span),
                         region, en_region);
     }
@@ -692,8 +692,8 @@ fn constrain_regions_in_type_of_node(
     let ty0 = rcx.resolve_node_type(id);
     let adjustment = rcx.fcx.inh.adjustments.find_copy(&id);
     let ty = ty::adjust_ty(tcx, origin.span(), ty0, adjustment);
-    debug!("constrain_regions_in_type_of_node(\
-            ty=%s, ty0=%s, id=%d, minimum_lifetime=%?, adjustment=%?)",
+    debug2!("constrain_regions_in_type_of_node(\
+            ty={}, ty0={}, id={}, minimum_lifetime={:?}, adjustment={:?})",
            ty_to_str(tcx, ty), ty_to_str(tcx, ty0),
            id, minimum_lifetime, adjustment);
     constrain_regions_in_type(rcx, minimum_lifetime, origin, ty)
@@ -722,12 +722,12 @@ fn constrain_regions_in_type(
     let e = rcx.errors_reported;
     let tcx = rcx.fcx.ccx.tcx;
 
-    debug!("constrain_regions_in_type(minimum_lifetime=%s, ty=%s)",
+    debug2!("constrain_regions_in_type(minimum_lifetime={}, ty={})",
            region_to_str(tcx, "", false, minimum_lifetime),
            ty_to_str(tcx, ty));
 
     do relate_nested_regions(tcx, Some(minimum_lifetime), ty) |r_sub, r_sup| {
-        debug!("relate(r_sub=%s, r_sup=%s)",
+        debug2!("relate(r_sub={}, r_sup={})",
                region_to_str(tcx, "", false, r_sub),
                region_to_str(tcx, "", false, r_sup));
 
@@ -813,7 +813,7 @@ pub mod guarantor {
          * to the lifetime of its guarantor (if any).
          */
 
-        debug!("guarantor::for_addr_of(base=?)");
+        debug2!("guarantor::for_addr_of(base=?)");
 
         let guarantor = guarantor(rcx, base);
         link(rcx, expr.span, expr.id, guarantor);
@@ -826,9 +826,9 @@ pub mod guarantor {
          * linked to the lifetime of its guarantor (if any).
          */
 
-        debug!("regionck::for_match()");
+        debug2!("regionck::for_match()");
         let discr_guarantor = guarantor(rcx, discr);
-        debug!("discr_guarantor=%s", discr_guarantor.repr(rcx.tcx()));
+        debug2!("discr_guarantor={}", discr_guarantor.repr(rcx.tcx()));
         for arm in arms.iter() {
             for pat in arm.pats.iter() {
                 link_ref_bindings_in_pat(rcx, *pat, discr_guarantor);
@@ -847,10 +847,10 @@ pub mod guarantor {
          * region pointers.
          */
 
-        debug!("guarantor::for_autoref(autoref=%?)", autoref);
+        debug2!("guarantor::for_autoref(autoref={:?})", autoref);
 
         let mut expr_ct = categorize_unadjusted(rcx, expr);
-        debug!("    unadjusted cat=%?", expr_ct.cat);
+        debug2!("    unadjusted cat={:?}", expr_ct.cat);
         expr_ct = apply_autoderefs(
             rcx, expr, autoderefs, expr_ct);
 
@@ -898,10 +898,10 @@ pub mod guarantor {
          */
 
         let tcx = rcx.tcx();
-        debug!("guarantor::for_by_ref(expr=%s, callee_scope=%?)",
+        debug2!("guarantor::for_by_ref(expr={}, callee_scope={:?})",
                expr.repr(tcx), callee_scope);
         let expr_cat = categorize(rcx, expr);
-        debug!("guarantor::for_by_ref(expr=%?, callee_scope=%?) category=%?",
+        debug2!("guarantor::for_by_ref(expr={:?}, callee_scope={:?}) category={:?}",
                expr.id, callee_scope, expr_cat);
         let minimum_lifetime = ty::re_scope(callee_scope);
         for guarantor in expr_cat.guarantor.iter() {
@@ -921,7 +921,7 @@ pub mod guarantor {
          * to the lifetime of its guarantor (if any).
          */
 
-        debug!("link(id=%?, guarantor=%?)", id, guarantor);
+        debug2!("link(id={:?}, guarantor={:?})", id, guarantor);
 
         let bound = match guarantor {
             None => {
@@ -939,7 +939,7 @@ pub mod guarantor {
         let rptr_ty = rcx.resolve_node_type(id);
         if !ty::type_is_bot(rptr_ty) {
             let tcx = rcx.fcx.ccx.tcx;
-            debug!("rptr_ty=%s", ty_to_str(tcx, rptr_ty));
+            debug2!("rptr_ty={}", ty_to_str(tcx, rptr_ty));
             let r = ty::ty_region(tcx, span, rptr_ty);
             rcx.fcx.mk_subr(true, infer::Reborrow(span), r, bound);
         }
@@ -977,7 +977,7 @@ pub mod guarantor {
          * `&expr`).
          */
 
-        debug!("guarantor()");
+        debug2!("guarantor()");
         match expr.node {
             ast::ExprUnary(_, ast::UnDeref, b) => {
                 let cat = categorize(rcx, b);
@@ -1035,15 +1035,15 @@ pub mod guarantor {
                     rcx.fcx.tcx(), rcx.fcx.inh.method_map, expr));
                 None
             }
-            ast::ExprForLoop(*) => fail!("non-desugared expr_for_loop"),
+            ast::ExprForLoop(*) => fail2!("non-desugared expr_for_loop"),
         }
     }
 
     fn categorize(rcx: &mut Rcx, expr: @ast::Expr) -> ExprCategorization {
-        debug!("categorize()");
+        debug2!("categorize()");
 
         let mut expr_ct = categorize_unadjusted(rcx, expr);
-        debug!("before adjustments, cat=%?", expr_ct.cat);
+        debug2!("before adjustments, cat={:?}", expr_ct.cat);
 
         match rcx.fcx.inh.adjustments.find(&expr.id) {
             Some(&@ty::AutoAddEnv(*)) => {
@@ -1056,7 +1056,7 @@ pub mod guarantor {
             }
 
             Some(&@ty::AutoDerefRef(ref adjustment)) => {
-                debug!("adjustment=%?", adjustment);
+                debug2!("adjustment={:?}", adjustment);
 
                 expr_ct = apply_autoderefs(
                     rcx, expr, adjustment.autoderefs, expr_ct);
@@ -1067,7 +1067,7 @@ pub mod guarantor {
                     Some(ty::AutoUnsafe(_)) => {
                         expr_ct.cat.guarantor = None;
                         expr_ct.cat.pointer = OtherPointer;
-                        debug!("autoref, cat=%?", expr_ct.cat);
+                        debug2!("autoref, cat={:?}", expr_ct.cat);
                     }
                     Some(ty::AutoPtr(r, _)) |
                     Some(ty::AutoBorrowVec(r, _)) |
@@ -1078,7 +1078,7 @@ pub mod guarantor {
                         // expression will be some sort of borrowed pointer.
                         expr_ct.cat.guarantor = None;
                         expr_ct.cat.pointer = BorrowedPointer(r);
-                        debug!("autoref, cat=%?", expr_ct.cat);
+                        debug2!("autoref, cat={:?}", expr_ct.cat);
                     }
                 }
             }
@@ -1086,14 +1086,14 @@ pub mod guarantor {
             None => {}
         }
 
-        debug!("result=%?", expr_ct.cat);
+        debug2!("result={:?}", expr_ct.cat);
         return expr_ct.cat;
     }
 
     fn categorize_unadjusted(rcx: &mut Rcx,
                              expr: @ast::Expr)
                           -> ExprCategorizationType {
-        debug!("categorize_unadjusted()");
+        debug2!("categorize_unadjusted()");
 
         let guarantor = {
             if rcx.fcx.inh.method_map.contains_key(&expr.id) {
@@ -1138,12 +1138,12 @@ pub mod guarantor {
                 None => {
                     tcx.sess.span_bug(
                         expr.span,
-                        fmt!("Autoderef but type not derefable: %s",
+                        format!("Autoderef but type not derefable: {}",
                              ty_to_str(tcx, ct.ty)));
                 }
             }
 
-            debug!("autoderef, cat=%?", ct.cat);
+            debug2!("autoderef, cat={:?}", ct.cat);
         }
         return ct;
     }
@@ -1205,7 +1205,7 @@ pub mod guarantor {
          * other pointers.
          */
 
-        debug!("link_ref_bindings_in_pat(pat=%s, guarantor=%?)",
+        debug2!("link_ref_bindings_in_pat(pat={}, guarantor={:?})",
                rcx.fcx.pat_to_str(pat), guarantor);
 
         match pat.node {
diff --git a/src/librustc/middle/typeck/check/regionmanip.rs b/src/librustc/middle/typeck/check/regionmanip.rs
index cb4827104b6..1aae00edf51 100644
--- a/src/librustc/middle/typeck/check/regionmanip.rs
+++ b/src/librustc/middle/typeck/check/regionmanip.rs
@@ -38,15 +38,15 @@ pub fn replace_bound_regions_in_fn_sig(
 
     for &t in opt_self_ty.iter() { all_tys.push(t) }
 
-    debug!("replace_bound_regions_in_fn_sig(self_ty=%?, fn_sig=%s, \
-            all_tys=%?)",
+    debug2!("replace_bound_regions_in_fn_sig(self_ty={:?}, fn_sig={}, \
+            all_tys={:?})",
            opt_self_ty.map(|t| ppaux::ty_to_str(tcx, *t)),
            ppaux::fn_sig_to_str(tcx, fn_sig),
            all_tys.map(|t| ppaux::ty_to_str(tcx, *t)));
     let _i = indenter();
 
     let isr = do create_bound_region_mapping(tcx, isr, all_tys) |br| {
-        debug!("br=%?", br);
+        debug2!("br={:?}", br);
         mapf(br)
     };
     let new_fn_sig = ty::fold_sig(fn_sig, |t| {
@@ -54,9 +54,9 @@ pub fn replace_bound_regions_in_fn_sig(
     });
     let new_self_ty = opt_self_ty.map(|t| replace_bound_regions(tcx, isr, *t));
 
-    debug!("result of replace_bound_regions_in_fn_sig: \
-            new_self_ty=%?, \
-            fn_sig=%s",
+    debug2!("result of replace_bound_regions_in_fn_sig: \
+            new_self_ty={:?}, \
+            fn_sig={}",
            new_self_ty.map(|t| ppaux::ty_to_str(tcx, *t)),
            ppaux::fn_sig_to_str(tcx, &new_fn_sig));
 
@@ -146,8 +146,8 @@ pub fn replace_bound_regions_in_fn_sig(
                   None if in_fn => r,
                   None => {
                     tcx.sess.bug(
-                        fmt!("Bound region not found in \
-                              in_scope_regions list: %s",
+                        format!("Bound region not found in \
+                              in_scope_regions list: {}",
                              region_to_str(tcx, "", false, r)));
                   }
                 }
@@ -255,7 +255,7 @@ pub fn relate_free_regions(
      * Tests: `src/test/compile-fail/regions-free-region-ordering-*.rs`
      */
 
-    debug!("relate_free_regions >>");
+    debug2!("relate_free_regions >>");
 
     let mut all_tys = ~[];
     for arg in fn_sig.inputs.iter() {
@@ -266,7 +266,7 @@ pub fn relate_free_regions(
     }
 
     for &t in all_tys.iter() {
-        debug!("relate_free_regions(t=%s)", ppaux::ty_to_str(tcx, t));
+        debug2!("relate_free_regions(t={})", ppaux::ty_to_str(tcx, t));
         relate_nested_regions(tcx, None, t, |a, b| {
             match (&a, &b) {
                 (&ty::re_free(free_a), &ty::re_free(free_b)) => {
@@ -277,5 +277,5 @@ pub fn relate_free_regions(
         })
     }
 
-    debug!("<< relate_free_regions");
+    debug2!("<< relate_free_regions");
 }
diff --git a/src/librustc/middle/typeck/check/vtable.rs b/src/librustc/middle/typeck/check/vtable.rs
index 0e153635720..146be8b85ad 100644
--- a/src/librustc/middle/typeck/check/vtable.rs
+++ b/src/librustc/middle/typeck/check/vtable.rs
@@ -87,9 +87,9 @@ fn lookup_vtables(vcx: &VtableContext,
                   type_param_defs: &[ty::TypeParameterDef],
                   substs: &ty::substs,
                   is_early: bool) -> vtable_res {
-    debug!("lookup_vtables(location_info=%?, \
-            type_param_defs=%s, \
-            substs=%s",
+    debug2!("lookup_vtables(location_info={:?}, \
+            type_param_defs={}, \
+            substs={}",
            location_info,
            type_param_defs.repr(vcx.tcx()),
            substs.repr(vcx.tcx()));
@@ -108,11 +108,11 @@ fn lookup_vtables(vcx: &VtableContext,
     result.reverse();
 
     assert_eq!(substs.tps.len(), result.len());
-    debug!("lookup_vtables result(\
-            location_info=%?, \
-            type_param_defs=%s, \
-            substs=%s, \
-            result=%s)",
+    debug2!("lookup_vtables result(\
+            location_info={:?}, \
+            type_param_defs={}, \
+            substs={}, \
+            result={})",
            location_info,
            type_param_defs.repr(vcx.tcx()),
            substs.repr(vcx.tcx()),
@@ -142,20 +142,20 @@ fn lookup_vtables_for_param(vcx: &VtableContext,
         // Substitute the values of the type parameters that may
         // appear in the bound.
         let trait_ref = substs.map_default(trait_ref, |substs| {
-            debug!("about to subst: %s, %s",
+            debug2!("about to subst: {}, {}",
                    trait_ref.repr(tcx), substs.repr(tcx));
             trait_ref.subst(tcx, *substs)
         });
 
-        debug!("after subst: %s", trait_ref.repr(tcx));
+        debug2!("after subst: {}", trait_ref.repr(tcx));
 
         match lookup_vtable(vcx, location_info, ty, trait_ref, is_early) {
             Some(vtable) => param_result.push(vtable),
             None => {
                 vcx.tcx().sess.span_fatal(
                     location_info.span,
-                    fmt!("failed to find an implementation of \
-                          trait %s for %s",
+                    format!("failed to find an implementation of \
+                          trait {} for {}",
                          vcx.infcx.trait_ref_to_str(trait_ref),
                          vcx.infcx.ty_to_str(ty)));
             }
@@ -163,11 +163,11 @@ fn lookup_vtables_for_param(vcx: &VtableContext,
         true
     };
 
-    debug!("lookup_vtables_for_param result(\
-            location_info=%?, \
-            type_param_bounds=%s, \
-            ty=%s, \
-            result=%s)",
+    debug2!("lookup_vtables_for_param result(\
+            location_info={:?}, \
+            type_param_bounds={}, \
+            ty={}, \
+            result={})",
            location_info,
            type_param_bounds.repr(vcx.tcx()),
            ty.repr(vcx.tcx()),
@@ -211,7 +211,7 @@ fn relate_trait_refs(vcx: &VtableContext,
                 let tcx = vcx.tcx();
                 tcx.sess.span_err(
                     location_info.span,
-                    fmt!("expected %s, but found %s (%s)",
+                    format!("expected {}, but found {} ({})",
                          ppaux::trait_ref_to_str(tcx, &r_exp_trait_ref),
                          ppaux::trait_ref_to_str(tcx, &r_act_trait_ref),
                          ty::type_err_to_str(tcx, err)));
@@ -228,7 +228,7 @@ fn lookup_vtable(vcx: &VtableContext,
                  is_early: bool)
     -> Option<vtable_origin>
 {
-    debug!("lookup_vtable(ty=%s, trait_ref=%s)",
+    debug2!("lookup_vtable(ty={}, trait_ref={})",
            vcx.infcx.ty_to_str(ty),
            vcx.infcx.trait_ref_to_str(trait_ref));
     let _i = indenter();
@@ -291,7 +291,7 @@ fn lookup_vtable_from_bounds(vcx: &VtableContext,
     let mut n_bound = 0;
     let mut ret = None;
     do ty::each_bound_trait_and_supertraits(tcx, bounds) |bound_trait_ref| {
-        debug!("checking bounds trait %s",
+        debug2!("checking bounds trait {}",
                bound_trait_ref.repr(vcx.tcx()));
 
         if bound_trait_ref.def_id == trait_ref.def_id {
@@ -300,7 +300,7 @@ fn lookup_vtable_from_bounds(vcx: &VtableContext,
                               bound_trait_ref,
                               trait_ref);
             let vtable = vtable_param(param, n_bound);
-            debug!("found param vtable: %?",
+            debug2!("found param vtable: {:?}",
                    vtable);
             ret = Some(vtable);
             false
@@ -383,7 +383,7 @@ fn search_for_vtable(vcx: &VtableContext,
 
         // Now, in the previous example, for_ty is bound to
         // the type self_ty, and substs is bound to [T].
-        debug!("The self ty is %s and its substs are %s",
+        debug2!("The self ty is {} and its substs are {}",
                vcx.infcx.ty_to_str(for_ty),
                vcx.infcx.tys_to_str(substs.tps));
 
@@ -397,8 +397,8 @@ fn search_for_vtable(vcx: &VtableContext,
         // some value of U) with some_trait<T>. This would fail if T
         // and U weren't compatible.
 
-        debug!("(checking vtable) @2 relating trait \
-                ty %s to of_trait_ref %s",
+        debug2!("(checking vtable) @2 relating trait \
+                ty {} to of_trait_ref {}",
                vcx.infcx.trait_ref_to_str(trait_ref),
                vcx.infcx.trait_ref_to_str(of_trait_ref));
 
@@ -435,9 +435,9 @@ fn search_for_vtable(vcx: &VtableContext,
             }
         };
 
-        debug!("The fixed-up substs are %s - \
+        debug2!("The fixed-up substs are {} - \
                 they will be unified with the bounds for \
-                the target ty, %s",
+                the target ty, {}",
                vcx.infcx.tys_to_str(substs_f.tps),
                vcx.infcx.trait_ref_to_str(trait_ref));
 
@@ -487,7 +487,7 @@ fn fixup_substs(vcx: &VtableContext,
     do fixup_ty(vcx, location_info, t, is_early).map |t_f| {
         match ty::get(*t_f).sty {
           ty::ty_trait(_, ref substs_f, _, _, _) => (*substs_f).clone(),
-          _ => fail!("t_f should be a trait")
+          _ => fail2!("t_f should be a trait")
         }
     }
 }
@@ -502,8 +502,8 @@ fn fixup_ty(vcx: &VtableContext,
         Err(e) if !is_early => {
             tcx.sess.span_fatal(
                 location_info.span,
-                fmt!("cannot determine a type \
-                      for this bounded type parameter: %s",
+                format!("cannot determine a type \
+                      for this bounded type parameter: {}",
                      fixup_err_to_str(e)))
         }
         Err(_) => {
@@ -533,7 +533,7 @@ fn connect_trait_tps(vcx: &VtableContext,
 fn insert_vtables(fcx: @mut FnCtxt,
                   callee_id: ast::NodeId,
                   vtables: vtable_res) {
-    debug!("insert_vtables(callee_id=%d, vtables=%?)",
+    debug2!("insert_vtables(callee_id={}, vtables={:?})",
            callee_id, vtables.repr(fcx.tcx()));
     fcx.inh.vtable_map.insert(callee_id, vtables);
 }
@@ -554,7 +554,7 @@ pub fn location_info_for_item(item: @ast::item) -> LocationInfo {
 pub fn early_resolve_expr(ex: @ast::Expr,
                           fcx: @mut FnCtxt,
                           is_early: bool) {
-    debug!("vtable: early_resolve_expr() ex with id %? (early: %b): %s",
+    debug2!("vtable: early_resolve_expr() ex with id {:?} (early: {}): {}",
            ex.id, is_early, expr_to_str(ex, fcx.tcx().sess.intr()));
     let _indent = indenter();
 
@@ -562,15 +562,15 @@ pub fn early_resolve_expr(ex: @ast::Expr,
     match ex.node {
       ast::ExprPath(*) => {
         do fcx.opt_node_ty_substs(ex.id) |substs| {
-            debug!("vtable resolution on parameter bounds for expr %s",
+            debug2!("vtable resolution on parameter bounds for expr {}",
                    ex.repr(fcx.tcx()));
             let def = cx.tcx.def_map.get_copy(&ex.id);
             let did = ast_util::def_id_of_def(def);
             let item_ty = ty::lookup_item_type(cx.tcx, did);
-            debug!("early resolve expr: def %? %?, %?, %s", ex.id, did, def,
+            debug2!("early resolve expr: def {:?} {:?}, {:?}, {}", ex.id, did, def,
                    fcx.infcx().ty_to_str(item_ty.ty));
             if has_trait_bounds(*item_ty.generics.type_param_defs) {
-                debug!("early_resolve_expr: looking up vtables for type params %s",
+                debug2!("early_resolve_expr: looking up vtables for type params {}",
                        item_ty.generics.type_param_defs.repr(fcx.tcx()));
                 let vcx = VtableContext { ccx: fcx.ccx, infcx: fcx.infcx() };
                 let vtbls = lookup_vtables(&vcx, &location_info_for_expr(ex),
@@ -596,7 +596,7 @@ pub fn early_resolve_expr(ex: @ast::Expr,
       ast::ExprMethodCall(callee_id, _, _, _, _, _) => {
         match ty::method_call_type_param_defs(cx.tcx, fcx.inh.method_map, ex.id) {
           Some(type_param_defs) => {
-            debug!("vtable resolution on parameter bounds for method call %s",
+            debug2!("vtable resolution on parameter bounds for method call {}",
                    ex.repr(fcx.tcx()));
             if has_trait_bounds(*type_param_defs) {
                 let substs = fcx.node_ty_substs(callee_id);
@@ -612,7 +612,7 @@ pub fn early_resolve_expr(ex: @ast::Expr,
         }
       }
       ast::ExprCast(src, _) => {
-          debug!("vtable resolution on expr %s", ex.repr(fcx.tcx()));
+          debug2!("vtable resolution on expr {}", ex.repr(fcx.tcx()));
           let target_ty = fcx.expr_ty(ex);
           match ty::get(target_ty).sty {
               // Bounds of type's contents are not checked here, but in kind.rs.
@@ -635,7 +635,7 @@ pub fn early_resolve_expr(ex: @ast::Expr,
                       (&ty::ty_rptr(_, mt), ty::RegionTraitStore(*))
                         if !mutability_allowed(mt.mutbl, target_mutbl) => {
                           fcx.tcx().sess.span_err(ex.span,
-                                                  fmt!("types differ in mutability"));
+                                                  format!("types differ in mutability"));
                       }
 
                       (&ty::ty_box(mt), ty::BoxTraitStore) |
@@ -691,24 +691,24 @@ pub fn early_resolve_expr(ex: @ast::Expr,
                       (_, ty::UniqTraitStore) => {
                           fcx.ccx.tcx.sess.span_err(
                               ex.span,
-                              fmt!("can only cast an ~-pointer \
-                                    to a ~-object, not a %s",
+                              format!("can only cast an ~-pointer \
+                                    to a ~-object, not a {}",
                                    ty::ty_sort_str(fcx.tcx(), ty)));
                       }
 
                       (_, ty::BoxTraitStore) => {
                           fcx.ccx.tcx.sess.span_err(
                               ex.span,
-                              fmt!("can only cast an @-pointer \
-                                    to an @-object, not a %s",
+                              format!("can only cast an @-pointer \
+                                    to an @-object, not a {}",
                                    ty::ty_sort_str(fcx.tcx(), ty)));
                       }
 
                       (_, ty::RegionTraitStore(_)) => {
                           fcx.ccx.tcx.sess.span_err(
                               ex.span,
-                              fmt!("can only cast an &-pointer \
-                                    to an &-object, not a %s",
+                              format!("can only cast an &-pointer \
+                                    to an &-object, not a {}",
                                    ty::ty_sort_str(fcx.tcx(), ty)));
                       }
                   }
@@ -753,7 +753,7 @@ pub fn resolve_impl(ccx: @mut CrateCtxt, impl_item: @ast::item) {
                 trait_bounds: ~[trait_ref]
             };
             let t = ty::node_id_to_type(ccx.tcx, impl_item.id);
-            debug!("=== Doing a self lookup now.");
+            debug2!("=== Doing a self lookup now.");
             // Right now, we don't have any place to store this.
             // We will need to make one so we can use this information
             // for compiling default methods that refer to supertraits.
diff --git a/src/librustc/middle/typeck/check/writeback.rs b/src/librustc/middle/typeck/check/writeback.rs
index 5e9ca576a56..4f281ce5f45 100644
--- a/src/librustc/middle/typeck/check/writeback.rs
+++ b/src/librustc/middle/typeck/check/writeback.rs
@@ -41,8 +41,8 @@ fn resolve_type_vars_in_type(fcx: @mut FnCtxt, sp: Span, typ: ty::t)
             if !fcx.ccx.tcx.sess.has_errors() {
                 fcx.ccx.tcx.sess.span_err(
                     sp,
-                    fmt!("cannot determine a type \
-                          for this expression: %s",
+                    format!("cannot determine a type \
+                          for this expression: {}",
                          infer::fixup_err_to_str(e)))
             }
             return None;
@@ -70,8 +70,8 @@ fn resolve_method_map_entry(fcx: @mut FnCtxt, sp: Span, id: ast::NodeId) {
                 for t in r.iter() {
                     let method_map = fcx.ccx.method_map;
                     let new_entry = method_map_entry { self_ty: *t, ..*mme };
-                    debug!("writeback::resolve_method_map_entry(id=%?, \
-                            new_entry=%?)",
+                    debug2!("writeback::resolve_method_map_entry(id={:?}, \
+                            new_entry={:?})",
                            id, new_entry);
                     method_map.insert(id, new_entry);
                 }
@@ -88,7 +88,7 @@ fn resolve_vtable_map_entry(fcx: @mut FnCtxt, sp: Span, id: ast::NodeId) {
             let r_origins = resolve_origins(fcx, sp, *origins);
             let vtable_map = fcx.ccx.vtable_map;
             vtable_map.insert(id, r_origins);
-            debug!("writeback::resolve_vtable_map_entry(id=%d, vtables=%?)",
+            debug2!("writeback::resolve_vtable_map_entry(id={}, vtables={:?})",
                    id, r_origins.repr(fcx.tcx()));
         }
     }
@@ -128,12 +128,12 @@ fn resolve_type_vars_for_node(wbcx: &mut WbCtxt, sp: Span, id: ast::NodeId)
                 Err(e) => {
                     // This should not, I think, happen:
                     fcx.ccx.tcx.sess.span_err(
-                        sp, fmt!("cannot resolve bound for closure: %s",
+                        sp, format!("cannot resolve bound for closure: {}",
                                  infer::fixup_err_to_str(e)));
                 }
                 Ok(r1) => {
                     let resolved_adj = @ty::AutoAddEnv(r1, s);
-                    debug!("Adjustments for node %d: %?", id, resolved_adj);
+                    debug2!("Adjustments for node {}: {:?}", id, resolved_adj);
                     fcx.tcx().adjustments.insert(id, resolved_adj);
                 }
             }
@@ -146,7 +146,7 @@ fn resolve_type_vars_for_node(wbcx: &mut WbCtxt, sp: Span, id: ast::NodeId)
                     Err(e) => {
                         // This should not, I think, happen.
                         fcx.ccx.tcx.sess.span_err(
-                            sp, fmt!("cannot resolve scope of borrow: %s",
+                            sp, format!("cannot resolve scope of borrow: {}",
                                      infer::fixup_err_to_str(e)));
                         r
                     }
@@ -162,7 +162,7 @@ fn resolve_type_vars_for_node(wbcx: &mut WbCtxt, sp: Span, id: ast::NodeId)
                 autoderefs: adj.autoderefs,
                 autoref: resolved_autoref,
             });
-            debug!("Adjustments for node %d: %?", id, resolved_adj);
+            debug2!("Adjustments for node {}: {:?}", id, resolved_adj);
             fcx.tcx().adjustments.insert(id, resolved_adj);
         }
     }
@@ -176,7 +176,7 @@ fn resolve_type_vars_for_node(wbcx: &mut WbCtxt, sp: Span, id: ast::NodeId)
       }
 
       Some(t) => {
-        debug!("resolve_type_vars_for_node(id=%d, n_ty=%s, t=%s)",
+        debug2!("resolve_type_vars_for_node(id={}, n_ty={}, t={})",
                id, ppaux::ty_to_str(tcx, n_ty), ppaux::ty_to_str(tcx, t));
         write_ty_to_tcx(tcx, id, t);
         let mut ret = Some(t);
@@ -284,7 +284,7 @@ fn visit_pat(p: @ast::Pat, wbcx: &mut WbCtxt) {
     }
 
     resolve_type_vars_for_node(wbcx, p.span, p.id);
-    debug!("Type for pattern binding %s (id %d) resolved to %s",
+    debug2!("Type for pattern binding {} (id {}) resolved to {}",
            pat_to_str(p, wbcx.fcx.ccx.tcx.sess.intr()), p.id,
            wbcx.fcx.infcx().ty_to_str(
                ty::node_id_to_type(wbcx.fcx.ccx.tcx,
@@ -297,7 +297,7 @@ fn visit_local(l: @ast::Local, wbcx: &mut WbCtxt) {
     let var_ty = wbcx.fcx.local_ty(l.span, l.id);
     match resolve_type(wbcx.fcx.infcx(), var_ty, resolve_all | force_all) {
         Ok(lty) => {
-            debug!("Type for local %s (id %d) resolved to %s",
+            debug2!("Type for local {} (id {}) resolved to {}",
                    pat_to_str(l.pat, wbcx.fcx.tcx().sess.intr()),
                    l.id,
                    wbcx.fcx.infcx().ty_to_str(lty));
@@ -306,8 +306,8 @@ fn visit_local(l: @ast::Local, wbcx: &mut WbCtxt) {
         Err(e) => {
             wbcx.fcx.ccx.tcx.sess.span_err(
                 l.span,
-                fmt!("cannot determine a type \
-                      for this local variable: %s",
+                format!("cannot determine a type \
+                      for this local variable: {}",
                      infer::fixup_err_to_str(e)));
             wbcx.success = false;
         }
diff --git a/src/librustc/middle/typeck/coherence.rs b/src/librustc/middle/typeck/coherence.rs
index 61d00dff584..f6c24e3cd23 100644
--- a/src/librustc/middle/typeck/coherence.rs
+++ b/src/librustc/middle/typeck/coherence.rs
@@ -76,7 +76,7 @@ pub fn get_base_type(inference_context: @mut InferCtxt,
 
     match get(resolved_type).sty {
         ty_enum(*) | ty_trait(*) | ty_struct(*) => {
-            debug!("(getting base type) found base type");
+            debug2!("(getting base type) found base type");
             Some(resolved_type)
         }
 
@@ -85,7 +85,7 @@ pub fn get_base_type(inference_context: @mut InferCtxt,
         ty_infer(*) | ty_param(*) | ty_self(*) | ty_type | ty_opaque_box |
         ty_opaque_closure_ptr(*) | ty_unboxed_vec(*) | ty_err | ty_box(_) |
         ty_uniq(_) | ty_ptr(_) | ty_rptr(_, _) => {
-            debug!("(getting base type) no base type; found %?",
+            debug2!("(getting base type) no base type; found {:?}",
                    get(original_type).sty);
             None
         }
@@ -135,7 +135,7 @@ pub fn get_base_type_def_id(inference_context: @mut InferCtxt,
                     return Some(def_id);
                 }
                 _ => {
-                    fail!("get_base_type() returned a type that wasn't an \
+                    fail2!("get_base_type() returned a type that wasn't an \
                            enum, struct, or trait");
                 }
             }
@@ -160,7 +160,7 @@ struct CoherenceCheckVisitor { cc: CoherenceChecker }
 impl visit::Visitor<()> for CoherenceCheckVisitor {
     fn visit_item(&mut self, item:@item, _:()) {
 
-//                debug!("(checking coherence) item '%s'",
+//                debug2!("(checking coherence) item '{}'",
 //                       self.cc.crate_context.tcx.sess.str_of(item.ident));
 
                 match item.node {
@@ -266,8 +266,8 @@ impl CoherenceChecker {
         // base type.
 
         if associated_traits.len() == 0 {
-            debug!("(checking implementation) no associated traits for item \
-                    '%s'",
+            debug2!("(checking implementation) no associated traits for item \
+                    '{}'",
                    self.crate_context.tcx.sess.str_of(item.ident));
 
             match get_base_type_def_id(self.inference_context,
@@ -290,7 +290,7 @@ impl CoherenceChecker {
         for associated_trait in associated_traits.iter() {
             let trait_ref = ty::node_id_to_trait_ref(
                 self.crate_context.tcx, associated_trait.ref_id);
-            debug!("(checking implementation) adding impl for trait '%s', item '%s'",
+            debug2!("(checking implementation) adding impl for trait '{}', item '{}'",
                    trait_ref.repr(self.crate_context.tcx),
                    self.crate_context.tcx.sess.str_of(item.ident));
 
@@ -325,7 +325,7 @@ impl CoherenceChecker {
                                        trait_ref: &ty::TraitRef,
                                        all_methods: &mut ~[@Method]) {
         let tcx = self.crate_context.tcx;
-        debug!("instantiate_default_methods(impl_id=%?, trait_ref=%s)",
+        debug2!("instantiate_default_methods(impl_id={:?}, trait_ref={})",
                impl_id, trait_ref.repr(tcx));
 
         let impl_poly_type = ty::lookup_item_type(tcx, impl_id);
@@ -336,7 +336,7 @@ impl CoherenceChecker {
             let new_id = tcx.sess.next_node_id();
             let new_did = local_def(new_id);
 
-            debug!("new_did=%? trait_method=%s", new_did, trait_method.repr(tcx));
+            debug2!("new_did={:?} trait_method={}", new_did, trait_method.repr(tcx));
 
             // Create substitutions for the various trait parameters.
             let new_method_ty =
@@ -348,7 +348,7 @@ impl CoherenceChecker {
                     *trait_method,
                     Some(trait_method.def_id));
 
-            debug!("new_method_ty=%s", new_method_ty.repr(tcx));
+            debug2!("new_method_ty={}", new_method_ty.repr(tcx));
             all_methods.push(new_method_ty);
 
             // construct the polytype for the method based on the method_ty
@@ -364,7 +364,7 @@ impl CoherenceChecker {
                 generics: new_generics,
                 ty: ty::mk_bare_fn(tcx, new_method_ty.fty.clone())
             };
-            debug!("new_polytype=%s", new_polytype.repr(tcx));
+            debug2!("new_polytype={}", new_polytype.repr(tcx));
 
             tcx.tcache.insert(new_did, new_polytype);
             tcx.methods.insert(new_did, new_method_ty);
@@ -440,7 +440,7 @@ impl CoherenceChecker {
                         let session = self.crate_context.tcx.sess;
                         session.span_err(
                             self.span_of_impl(implementation_b),
-                            fmt!("conflicting implementations for trait `%s`",
+                            format!("conflicting implementations for trait `{}`",
                                  ty::item_path_str(self.crate_context.tcx,
                                                    trait_def_id)));
                         session.span_note(self.span_of_impl(implementation_a),
@@ -557,11 +557,11 @@ impl CoherenceChecker {
 
         let r = ty::trait_methods(tcx, trait_did);
         for method in r.iter() {
-            debug!("checking for %s", method.ident.repr(tcx));
+            debug2!("checking for {}", method.ident.repr(tcx));
             if provided_names.contains(&method.ident.name) { loop; }
 
             tcx.sess.span_err(trait_ref_span,
-                              fmt!("missing method `%s`",
+                              format!("missing method `{}`",
                                    tcx.sess.str_of(method.ident)));
         }
     }
diff --git a/src/librustc/middle/typeck/collect.rs b/src/librustc/middle/typeck/collect.rs
index 3f5e1ef5210..e5b01fea061 100644
--- a/src/librustc/middle/typeck/collect.rs
+++ b/src/librustc/middle/typeck/collect.rs
@@ -129,8 +129,8 @@ impl AstConv for CrateCtxt {
                 ty_of_foreign_item(self, foreign_item, abis)
               }
               ref x => {
-                self.tcx.sess.bug(fmt!("unexpected sort of item \
-                                        in get_item_ty(): %?", (*x)));
+                self.tcx.sess.bug(format!("unexpected sort of item \
+                                        in get_item_ty(): {:?}", (*x)));
               }
             }
         }
@@ -347,7 +347,7 @@ pub fn ensure_trait_methods(ccx: &CrateCtxt,
         let substd_type_param_defs = m.generics.type_param_defs.subst(tcx, &substs);
         new_type_param_defs.push_all(*substd_type_param_defs);
 
-        debug!("static method %s type_param_defs=%s ty=%s, substs=%s",
+        debug2!("static method {} type_param_defs={} ty={}, substs={}",
                m.def_id.repr(tcx),
                new_type_param_defs.repr(tcx),
                ty.repr(tcx),
@@ -453,7 +453,7 @@ pub fn compare_impl_method(tcx: ty::ctxt,
                            trait_m: &ty::Method,
                            trait_substs: &ty::substs,
                            self_ty: ty::t) {
-    debug!("compare_impl_method()");
+    debug2!("compare_impl_method()");
     let infcx = infer::new_infer_ctxt(tcx);
 
     let impl_m = &cm.mty;
@@ -470,7 +470,7 @@ pub fn compare_impl_method(tcx: ty::ctxt,
         (&ast::sty_static, _) => {
             tcx.sess.span_err(
                 cm.span,
-                fmt!("method `%s` has a `%s` declaration in the impl, \
+                format!("method `{}` has a `{}` declaration in the impl, \
                       but not in the trait",
                      tcx.sess.str_of(trait_m.ident),
                      explicit_self_to_str(&impl_m.explicit_self, tcx.sess.intr())));
@@ -479,7 +479,7 @@ pub fn compare_impl_method(tcx: ty::ctxt,
         (_, &ast::sty_static) => {
             tcx.sess.span_err(
                 cm.span,
-                fmt!("method `%s` has a `%s` declaration in the trait, \
+                format!("method `{}` has a `{}` declaration in the trait, \
                       but not in the impl",
                      tcx.sess.str_of(trait_m.ident),
                      explicit_self_to_str(&trait_m.explicit_self, tcx.sess.intr())));
@@ -495,8 +495,8 @@ pub fn compare_impl_method(tcx: ty::ctxt,
     if num_impl_m_type_params != num_trait_m_type_params {
         tcx.sess.span_err(
             cm.span,
-            fmt!("method `%s` has %u type %s, but its trait \
-                  declaration has %u type %s",
+            format!("method `{}` has {} type {}, but its trait \
+                  declaration has {} type {}",
                  tcx.sess.str_of(trait_m.ident),
                  num_impl_m_type_params,
                  pluralize(num_impl_m_type_params, ~"parameter"),
@@ -508,8 +508,8 @@ pub fn compare_impl_method(tcx: ty::ctxt,
     if impl_m.fty.sig.inputs.len() != trait_m.fty.sig.inputs.len() {
         tcx.sess.span_err(
             cm.span,
-            fmt!("method `%s` has %u parameter%s \
-                  but the trait has %u",
+            format!("method `{}` has {} parameter{} \
+                  but the trait has {}",
                  tcx.sess.str_of(trait_m.ident),
                  impl_m.fty.sig.inputs.len(),
                  if impl_m.fty.sig.inputs.len() == 1 { "" } else { "s" },
@@ -529,8 +529,8 @@ pub fn compare_impl_method(tcx: ty::ctxt,
         if !extra_bounds.is_empty() {
            tcx.sess.span_err(
                cm.span,
-               fmt!("in method `%s`, \
-                     type parameter %u requires `%s`, \
+               format!("in method `{}`, \
+                     type parameter {} requires `{}`, \
                      which is not required by \
                      the corresponding type parameter \
                      in the trait declaration",
@@ -548,10 +548,10 @@ pub fn compare_impl_method(tcx: ty::ctxt,
         {
             tcx.sess.span_err(
                 cm.span,
-                fmt!("in method `%s`, \
-                      type parameter %u has %u trait %s, but the \
+                format!("in method `{}`, \
+                      type parameter {} has {} trait {}, but the \
                       corresponding type parameter in \
-                      the trait declaration has %u trait %s",
+                      the trait declaration has {} trait {}",
                      tcx.sess.str_of(trait_m.ident),
                      i, impl_param_def.bounds.trait_bounds.len(),
                      pluralize(impl_param_def.bounds.trait_bounds.len(),
@@ -632,10 +632,10 @@ pub fn compare_impl_method(tcx: ty::ctxt,
     //   that correspond to the parameters we will find on the impl
     // - replace self region with a fresh, dummy region
     let impl_fty = {
-        debug!("impl_fty (pre-subst): %s", ppaux::ty_to_str(tcx, impl_fty));
+        debug2!("impl_fty (pre-subst): {}", ppaux::ty_to_str(tcx, impl_fty));
         replace_bound_self(tcx, impl_fty, dummy_self_r)
     };
-    debug!("impl_fty (post-subst): %s", ppaux::ty_to_str(tcx, impl_fty));
+    debug2!("impl_fty (post-subst): {}", ppaux::ty_to_str(tcx, impl_fty));
     let trait_fty = {
         let num_trait_m_type_params = trait_m.generics.type_param_defs.len();
         let dummy_tps = do vec::from_fn(num_trait_m_type_params) |i| {
@@ -649,11 +649,11 @@ pub fn compare_impl_method(tcx: ty::ctxt,
             self_ty: Some(self_ty),
             tps: vec::append(trait_tps, dummy_tps)
         };
-        debug!("trait_fty (pre-subst): %s substs=%s",
+        debug2!("trait_fty (pre-subst): {} substs={}",
                trait_fty.repr(tcx), substs.repr(tcx));
         ty::subst(tcx, &substs, trait_fty)
     };
-    debug!("trait_fty (post-subst): %s", trait_fty.repr(tcx));
+    debug2!("trait_fty (post-subst): {}", trait_fty.repr(tcx));
 
     match infer::mk_subty(infcx, false, infer::MethodCompatCheck(cm.span),
                           impl_fty, trait_fty) {
@@ -661,7 +661,7 @@ pub fn compare_impl_method(tcx: ty::ctxt,
         result::Err(ref terr) => {
             tcx.sess.span_err(
                 cm.span,
-                fmt!("method `%s` has an incompatible type: %s",
+                format!("method `{}` has an incompatible type: {}",
                      tcx.sess.str_of(trait_m.ident),
                      ty::type_err_to_str(tcx, terr)));
             ty::note_and_explain_type_err(tcx, terr);
@@ -709,7 +709,7 @@ pub fn check_methods_against_trait(ccx: &CrateCtxt,
                 // This method is not part of the trait
                 tcx.sess.span_err(
                     impl_m.span,
-                    fmt!("method `%s` is not a member of trait `%s`",
+                    format!("method `{}` is not a member of trait `{}`",
                          tcx.sess.str_of(impl_m.mty.ident),
                          path_to_str(&a_trait_ty.path, tcx.sess.intr())));
             }
@@ -835,7 +835,7 @@ pub fn ensure_no_ty_param_bounds(ccx: &CrateCtxt,
         if ty_param.bounds.len() > 0 {
             ccx.tcx.sess.span_err(
                 span,
-                fmt!("trait bounds are not allowed in %s definitions",
+                format!("trait bounds are not allowed in {} definitions",
                      thing));
         }
     }
@@ -844,7 +844,7 @@ pub fn ensure_no_ty_param_bounds(ccx: &CrateCtxt,
 pub fn convert(ccx: &CrateCtxt, it: &ast::item) {
     let tcx = ccx.tcx;
     let rp = tcx.region_paramd_items.find(&it.id).map_move(|x| *x);
-    debug!("convert: item %s with id %d rp %?",
+    debug2!("convert: item {} with id {} rp {:?}",
            tcx.sess.str_of(it.ident), it.id, rp);
     match it.node {
       // These don't define types.
@@ -1000,8 +1000,8 @@ pub fn convert_foreign(ccx: &CrateCtxt, i: &ast::foreign_item) {
     let abis = match ccx.tcx.items.find(&i.id) {
         Some(&ast_map::node_foreign_item(_, abis, _, _)) => abis,
         ref x => {
-            ccx.tcx.sess.bug(fmt!("unexpected sort of item \
-                                   in get_item_ty(): %?", (*x)));
+            ccx.tcx.sess.bug(format!("unexpected sort of item \
+                                   in get_item_ty(): {:?}", (*x)));
         }
     };
 
@@ -1038,7 +1038,7 @@ pub fn instantiate_trait_ref(ccx: &CrateCtxt,
         _ => {
             ccx.tcx.sess.span_fatal(
                 ast_trait_ref.path.span,
-                fmt!("%s is not a trait",
+                format!("{} is not a trait",
                     path_to_str(&ast_trait_ref.path,
                                 ccx.tcx.sess.intr())));
         }
@@ -1051,7 +1051,7 @@ fn get_trait_def(ccx: &CrateCtxt, trait_id: ast::DefId) -> @ty::TraitDef {
     } else {
         match ccx.tcx.items.get(&trait_id.node) {
             &ast_map::node_item(item, _) => trait_def_of_item(ccx, item),
-            _ => ccx.tcx.sess.bug(fmt!("get_trait_def(%d): not an item",
+            _ => ccx.tcx.sess.bug(format!("get_trait_def({}): not an item",
                                        trait_id.node))
         }
     }
@@ -1083,7 +1083,7 @@ pub fn trait_def_of_item(ccx: &CrateCtxt, it: &ast::item) -> @ty::TraitDef {
         ref s => {
             tcx.sess.span_bug(
                 it.span,
-                fmt!("trait_def_of_item invoked on %?", s));
+                format!("trait_def_of_item invoked on {:?}", s));
         }
     }
 }
@@ -1120,7 +1120,7 @@ pub fn ty_of_item(ccx: &CrateCtxt, it: &ast::item)
             },
             ty: ty::mk_bare_fn(ccx.tcx, tofd)
         };
-        debug!("type of %s (id %d) is %s",
+        debug2!("type of {} (id {}) is {}",
                tcx.sess.str_of(it.ident),
                it.id,
                ppaux::ty_to_str(tcx, tpt.ty));
@@ -1161,7 +1161,7 @@ pub fn ty_of_item(ccx: &CrateCtxt, it: &ast::item)
       ast::item_trait(*) => {
           tcx.sess.span_bug(
               it.span,
-              fmt!("Invoked ty_of_item on trait"));
+              format!("Invoked ty_of_item on trait"));
       }
       ast::item_struct(_, ref generics) => {
           let (ty_generics, substs) = mk_item_substs(ccx, generics, rp, None);
@@ -1174,8 +1174,8 @@ pub fn ty_of_item(ccx: &CrateCtxt, it: &ast::item)
           return tpt;
       }
       ast::item_impl(*) | ast::item_mod(_) |
-      ast::item_foreign_mod(_) => fail!(),
-      ast::item_mac(*) => fail!("item macros unimplemented")
+      ast::item_foreign_mod(_) => fail2!(),
+      ast::item_mac(*) => fail2!("item macros unimplemented")
     }
 }
 
@@ -1222,7 +1222,7 @@ pub fn ty_generics(ccx: &CrateCtxt,
                         def_id: local_def(param.id),
                         bounds: bounds
                     };
-                    debug!("def for param: %s", def.repr(ccx.tcx));
+                    debug2!("def for param: {}", def.repr(ccx.tcx));
                     ccx.tcx.ty_param_defs.insert(param.id, def);
                     def
                 }
diff --git a/src/librustc/middle/typeck/infer/coercion.rs b/src/librustc/middle/typeck/infer/coercion.rs
index 99c7725c7a2..8d1eaf34256 100644
--- a/src/librustc/middle/typeck/infer/coercion.rs
+++ b/src/librustc/middle/typeck/infer/coercion.rs
@@ -87,7 +87,7 @@ pub struct Coerce(CombineFields);
 
 impl Coerce {
     pub fn tys(&self, a: ty::t, b: ty::t) -> CoerceResult {
-        debug!("Coerce.tys(%s => %s)",
+        debug2!("Coerce.tys({} => {})",
                a.inf_str(self.infcx),
                b.inf_str(self.infcx));
         let _indent = indenter();
@@ -172,8 +172,8 @@ impl Coerce {
             Err(e) => {
                 self.infcx.tcx.sess.span_bug(
                     self.trace.origin.span(),
-                    fmt!("Failed to resolve even without \
-                          any force options: %?", e));
+                    format!("Failed to resolve even without \
+                          any force options: {:?}", e));
             }
         }
     }
@@ -184,7 +184,7 @@ impl Coerce {
                                    b: ty::t,
                                    mt_b: ty::mt)
                                    -> CoerceResult {
-        debug!("coerce_borrowed_pointer(a=%s, sty_a=%?, b=%s, mt_b=%?)",
+        debug2!("coerce_borrowed_pointer(a={}, sty_a={:?}, b={}, mt_b={:?})",
                a.inf_str(self.infcx), sty_a,
                b.inf_str(self.infcx), mt_b);
 
@@ -221,7 +221,7 @@ impl Coerce {
                                   sty_a: &ty::sty,
                                   b: ty::t)
                                   -> CoerceResult {
-        debug!("coerce_borrowed_string(a=%s, sty_a=%?, b=%s)",
+        debug2!("coerce_borrowed_string(a={}, sty_a={:?}, b={})",
                a.inf_str(self.infcx), sty_a,
                b.inf_str(self.infcx));
 
@@ -248,7 +248,7 @@ impl Coerce {
                                   b: ty::t,
                                   mt_b: ty::mt)
                                   -> CoerceResult {
-        debug!("coerce_borrowed_vector(a=%s, sty_a=%?, b=%s)",
+        debug2!("coerce_borrowed_vector(a={}, sty_a={:?}, b={})",
                a.inf_str(self.infcx), sty_a,
                b.inf_str(self.infcx));
 
@@ -277,7 +277,7 @@ impl Coerce {
                               b: ty::t,
                               b_mutbl: ast::Mutability) -> CoerceResult
     {
-        debug!("coerce_borrowed_object(a=%s, sty_a=%?, b=%s)",
+        debug2!("coerce_borrowed_object(a={}, sty_a={:?}, b={})",
                a.inf_str(self.infcx), sty_a,
                b.inf_str(self.infcx));
 
@@ -306,7 +306,7 @@ impl Coerce {
                               sty_a: &ty::sty,
                               b: ty::t)
                               -> CoerceResult {
-        debug!("coerce_borrowed_fn(a=%s, sty_a=%?, b=%s)",
+        debug2!("coerce_borrowed_fn(a={}, sty_a={:?}, b={})",
                a.inf_str(self.infcx), sty_a,
                b.inf_str(self.infcx));
 
@@ -361,7 +361,7 @@ impl Coerce {
          * "rust" fn`) into a closure.
          */
 
-        debug!("coerce_from_bare_fn(a=%s, b=%s)",
+        debug2!("coerce_from_bare_fn(a={}, b={})",
                a.inf_str(self.infcx), b.inf_str(self.infcx));
 
         if !fn_ty_a.abis.is_rust() {
@@ -389,7 +389,7 @@ impl Coerce {
                              b: ty::t,
                              mt_b: ty::mt)
                              -> CoerceResult {
-        debug!("coerce_unsafe_ptr(a=%s, sty_a=%?, b=%s)",
+        debug2!("coerce_unsafe_ptr(a={}, sty_a={:?}, b={})",
                a.inf_str(self.infcx), sty_a,
                b.inf_str(self.infcx));
 
diff --git a/src/librustc/middle/typeck/infer/combine.rs b/src/librustc/middle/typeck/infer/combine.rs
index cdfb8732a38..3f6248eae12 100644
--- a/src/librustc/middle/typeck/infer/combine.rs
+++ b/src/librustc/middle/typeck/infer/combine.rs
@@ -116,7 +116,7 @@ pub trait Combine {
                 // substs and one of them has a self_ty and one
                 // doesn't...? I could be wrong about this.
                 self.infcx().tcx.sess.bug(
-                                          fmt!("substitution a had a self_ty \
+                                          format!("substitution a had a self_ty \
                                                and substitution b didn't, \
                                                or vice versa"));
             }
@@ -270,7 +270,7 @@ pub trait Combine {
     fn vstores(&self, vk: ty::terr_vstore_kind,
                a: ty::vstore, b: ty::vstore) -> cres<ty::vstore> {
 
-        debug!("%s.vstores(a=%?, b=%?)", self.tag(), a, b);
+        debug2!("{}.vstores(a={:?}, b={:?})", self.tag(), a, b);
 
         match (a, b) {
             (ty::vstore_slice(a_r), ty::vstore_slice(b_r)) => {
@@ -295,7 +295,7 @@ pub trait Combine {
                     b: ty::TraitStore)
                  -> cres<ty::TraitStore> {
 
-        debug!("%s.trait_stores(a=%?, b=%?)", self.tag(), a, b);
+        debug2!("{}.trait_stores(a={:?}, b={:?})", self.tag(), a, b);
 
         match (a, b) {
             (ty::RegionTraitStore(a_r), ty::RegionTraitStore(b_r)) => {
@@ -365,7 +365,7 @@ pub fn eq_tys<C:Combine>(this: &C, a: ty::t, b: ty::t) -> ures {
 
 pub fn eq_regions<C:Combine>(this: &C, a: ty::Region, b: ty::Region)
                           -> ures {
-    debug!("eq_regions(%s, %s)",
+    debug2!("eq_regions({}, {})",
            a.inf_str(this.infcx()),
            b.inf_str(this.infcx()));
     let sub = this.sub();
@@ -406,8 +406,8 @@ pub fn eq_opt_regions<C:Combine>(
         // consistently have a region parameter or not have a
         // region parameter.
         this.infcx().tcx.sess.bug(
-            fmt!("substitution a had opt_region %s and \
-                  b had opt_region %s",
+            format!("substitution a had opt_region {} and \
+                  b had opt_region {}",
                  a.inf_str(this.infcx()),
                  b.inf_str(this.infcx())));
       }
@@ -446,7 +446,7 @@ pub fn super_tys<C:Combine>(
       (&ty::ty_infer(TyVar(_)), _) |
       (_, &ty::ty_infer(TyVar(_))) => {
         tcx.sess.bug(
-            fmt!("%s: bot and var types should have been handled (%s,%s)",
+            format!("{}: bot and var types should have been handled ({},{})",
                  this.tag(),
                  a.inf_str(this.infcx()),
                  b.inf_str(this.infcx())));
diff --git a/src/librustc/middle/typeck/infer/error_reporting.rs b/src/librustc/middle/typeck/infer/error_reporting.rs
index 2c8e7b28059..3f38850c8ff 100644
--- a/src/librustc/middle/typeck/infer/error_reporting.rs
+++ b/src/librustc/middle/typeck/infer/error_reporting.rs
@@ -163,7 +163,7 @@ impl ErrorReporting for InferCtxt {
 
         self.tcx.sess.span_err(
             trace.origin.span(),
-            fmt!("%s: %s (%s)",
+            format!("{}: {} ({})",
                  message_root_str,
                  expected_found_str,
                  ty::type_err_to_str(tcx, terr)));
@@ -173,7 +173,7 @@ impl ErrorReporting for InferCtxt {
 
     fn values_str(@mut self, values: &ValuePairs) -> Option<~str> {
         /*!
-         * Returns a string of the form "expected `%s` but found `%s`",
+         * Returns a string of the form "expected `{}` but found `{}`",
          * or None if this is a derived error.
          */
         match *values {
@@ -201,7 +201,7 @@ impl ErrorReporting for InferCtxt {
             return None;
         }
 
-        Some(fmt!("expected `%s` but found `%s`",
+        Some(format!("expected `{}` but found `{}`",
                   expected.user_string(self.tcx),
                   found.user_string(self.tcx)))
     }
@@ -284,7 +284,7 @@ impl ErrorReporting for InferCtxt {
             infer::IndexSlice(span) => {
                 self.tcx.sess.span_err(
                     span,
-                    fmt!("index of slice outside its lifetime"));
+                    format!("index of slice outside its lifetime"));
                 note_and_explain_region(
                     self.tcx,
                     "the slice is only valid for ",
@@ -375,7 +375,7 @@ impl ErrorReporting for InferCtxt {
             infer::ReferenceOutlivesReferent(ty, span) => {
                 self.tcx.sess.span_err(
                     span,
-                    fmt!("in type `%s`, pointer has a longer lifetime than \
+                    format!("in type `{}`, pointer has a longer lifetime than \
                           the data it references",
                          ty.user_string(self.tcx)));
                 note_and_explain_region(
@@ -400,7 +400,7 @@ impl ErrorReporting for InferCtxt {
                                sup_region: Region) {
         self.tcx.sess.span_err(
             var_origin.span(),
-            fmt!("cannot infer an appropriate lifetime \
+            format!("cannot infer an appropriate lifetime \
                   due to conflicting requirements"));
 
         note_and_explain_region(
@@ -411,7 +411,7 @@ impl ErrorReporting for InferCtxt {
 
         self.tcx.sess.span_note(
             sup_origin.span(),
-            fmt!("...due to the following expression"));
+            format!("...due to the following expression"));
 
         note_and_explain_region(
             self.tcx,
@@ -421,7 +421,7 @@ impl ErrorReporting for InferCtxt {
 
         self.tcx.sess.span_note(
             sub_origin.span(),
-            fmt!("...due to the following expression"));
+            format!("...due to the following expression"));
     }
 
     fn report_sup_sup_conflict(@mut self,
@@ -432,7 +432,7 @@ impl ErrorReporting for InferCtxt {
                                region2: Region) {
         self.tcx.sess.span_err(
             var_origin.span(),
-            fmt!("cannot infer an appropriate lifetime \
+            format!("cannot infer an appropriate lifetime \
                   due to conflicting requirements"));
 
         note_and_explain_region(
@@ -443,7 +443,7 @@ impl ErrorReporting for InferCtxt {
 
         self.tcx.sess.span_note(
             origin1.span(),
-            fmt!("...due to the following expression"));
+            format!("...due to the following expression"));
 
         note_and_explain_region(
             self.tcx,
@@ -453,7 +453,7 @@ impl ErrorReporting for InferCtxt {
 
         self.tcx.sess.span_note(
             origin2.span(),
-            fmt!("...due to the following expression"));
+            format!("...due to the following expression"));
     }
 }
 
diff --git a/src/librustc/middle/typeck/infer/glb.rs b/src/librustc/middle/typeck/infer/glb.rs
index af62da5fde0..5e9eb51cbb6 100644
--- a/src/librustc/middle/typeck/infer/glb.rs
+++ b/src/librustc/middle/typeck/infer/glb.rs
@@ -44,7 +44,7 @@ impl Combine for Glb {
     fn mts(&self, a: &ty::mt, b: &ty::mt) -> cres<ty::mt> {
         let tcx = self.infcx.tcx;
 
-        debug!("%s.mts(%s, %s)",
+        debug2!("{}.mts({}, {})",
                self.tag(),
                mt_to_str(tcx, a),
                mt_to_str(tcx, b));
@@ -100,7 +100,7 @@ impl Combine for Glb {
     }
 
     fn regions(&self, a: ty::Region, b: ty::Region) -> cres<ty::Region> {
-        debug!("%s.regions(%?, %?)",
+        debug2!("{}.regions({:?}, {:?})",
                self.tag(),
                a.inf_str(self.infcx),
                b.inf_str(self.infcx));
@@ -121,7 +121,7 @@ impl Combine for Glb {
         // Note: this is a subtle algorithm.  For a full explanation,
         // please see the large comment in `region_inference.rs`.
 
-        debug!("%s.fn_sigs(%?, %?)",
+        debug2!("{}.fn_sigs({:?}, {:?})",
                self.tag(), a.inf_str(self.infcx), b.inf_str(self.infcx));
         let _indenter = indenter();
 
@@ -143,7 +143,7 @@ impl Combine for Glb {
 
         // Collect constraints.
         let sig0 = if_ok!(super_fn_sigs(self, &a_with_fresh, &b_with_fresh));
-        debug!("sig0 = %s", sig0.inf_str(self.infcx));
+        debug2!("sig0 = {}", sig0.inf_str(self.infcx));
 
         // Generalize the regions appearing in fn_ty0 if possible
         let new_vars =
@@ -155,7 +155,7 @@ impl Combine for Glb {
                 |r, _in_fn| generalize_region(self, snapshot,
                                               new_vars, a_isr, a_vars, b_vars,
                                               r));
-        debug!("sig1 = %s", sig1.inf_str(self.infcx));
+        debug2!("sig1 = {}", sig1.inf_str(self.infcx));
         return Ok(sig1);
 
         fn generalize_region(this: &Glb,
@@ -237,7 +237,7 @@ impl Combine for Glb {
                 Some(x) => x,
                 None => this.infcx.tcx.sess.span_bug(
                             this.trace.origin.span(),
-                            fmt!("could not find original bound region for %?", r))
+                            format!("could not find original bound region for {:?}", r))
             }
         }
 
diff --git a/src/librustc/middle/typeck/infer/lattice.rs b/src/librustc/middle/typeck/infer/lattice.rs
index 4cbdf9fa1fb..919ad68a818 100644
--- a/src/librustc/middle/typeck/infer/lattice.rs
+++ b/src/librustc/middle/typeck/infer/lattice.rs
@@ -131,7 +131,7 @@ impl CombineFieldsLatticeMethods for CombineFields {
         let a_bounds = node_a.possible_types.clone();
         let b_bounds = node_b.possible_types.clone();
 
-        debug!("vars(%s=%s <: %s=%s)",
+        debug2!("vars({}={} <: {}={})",
                a_id.to_str(), a_bounds.inf_str(self.infcx),
                b_id.to_str(), b_bounds.inf_str(self.infcx));
 
@@ -179,7 +179,7 @@ impl CombineFieldsLatticeMethods for CombineFields {
         let a_bounds = &node_a.possible_types;
         let b_bounds = &Bounds { lb: None, ub: Some(b.clone()) };
 
-        debug!("var_sub_t(%s=%s <: %s)",
+        debug2!("var_sub_t({}={} <: {})",
                a_id.to_str(),
                a_bounds.inf_str(self.infcx),
                b.inf_str(self.infcx));
@@ -203,7 +203,7 @@ impl CombineFieldsLatticeMethods for CombineFields {
         let b_id = node_b.root.clone();
         let b_bounds = &node_b.possible_types;
 
-        debug!("t_sub_var(%s <: %s=%s)",
+        debug2!("t_sub_var({} <: {}={})",
                a.inf_str(self.infcx),
                b_id.to_str(),
                b_bounds.inf_str(self.infcx));
@@ -222,7 +222,7 @@ impl CombineFieldsLatticeMethods for CombineFields {
          *
          * Combines two bounds into a more general bound. */
 
-        debug!("merge_bnd(%s,%s)",
+        debug2!("merge_bnd({},{})",
                a.inf_str(self.infcx),
                b.inf_str(self.infcx));
         let _r = indenter();
@@ -273,7 +273,7 @@ impl CombineFieldsLatticeMethods for CombineFields {
         //       A     \ / A
         //              B
 
-        debug!("merge(%s,%s,%s)",
+        debug2!("merge({},{},{})",
                v_id.to_str(),
                a.inf_str(self.infcx),
                b.inf_str(self.infcx));
@@ -290,7 +290,7 @@ impl CombineFieldsLatticeMethods for CombineFields {
         let ub = if_ok!(self.merge_bnd(&a.ub, &b.ub, LatticeValue::glb));
         let lb = if_ok!(self.merge_bnd(&a.lb, &b.lb, LatticeValue::lub));
         let bounds = Bounds { lb: lb, ub: ub };
-        debug!("merge(%s): bounds=%s",
+        debug2!("merge({}): bounds={}",
                v_id.to_str(),
                bounds.inf_str(self.infcx));
 
@@ -305,7 +305,7 @@ impl CombineFieldsLatticeMethods for CombineFields {
                                                a: &Bound<T>,
                                                b: &Bound<T>)
                                                -> ures {
-        debug!("bnds(%s <: %s)", a.inf_str(self.infcx),
+        debug2!("bnds({} <: {})", a.inf_str(self.infcx),
                b.inf_str(self.infcx));
         let _r = indenter();
 
@@ -370,7 +370,7 @@ pub fn super_lattice_tys<L:LatticeDir + TyLatticeDir + Combine>(
     this: &L,
     a: ty::t,
     b: ty::t) -> cres<ty::t> {
-    debug!("%s.lattice_tys(%s, %s)", this.tag(),
+    debug2!("{}.lattice_tys({}, {})", this.tag(),
            a.inf_str(this.infcx()),
            b.inf_str(this.infcx()));
     let _r = indenter();
@@ -448,7 +448,7 @@ pub fn lattice_vars<L:LatticeDir + Combine,
     let a_bounds = &nde_a.possible_types;
     let b_bounds = &nde_b.possible_types;
 
-    debug!("%s.lattice_vars(%s=%s <: %s=%s)",
+    debug2!("{}.lattice_vars({}={} <: {}={})",
            this.tag(),
            a_vid.to_str(), a_bounds.inf_str(this.infcx()),
            b_vid.to_str(), b_bounds.inf_str(this.infcx()));
@@ -494,7 +494,7 @@ pub fn lattice_var_and_t<L:LatticeDir + Combine,
     // The comments in this function are written for LUB, but they
     // apply equally well to GLB if you inverse upper/lower/sub/super/etc.
 
-    debug!("%s.lattice_var_and_t(%s=%s <: %s)",
+    debug2!("{}.lattice_var_and_t({}={} <: {})",
            this.tag(),
            a_id.to_str(),
            a_bounds.inf_str(this.infcx()),
@@ -503,13 +503,13 @@ pub fn lattice_var_and_t<L:LatticeDir + Combine,
     match this.bnd(a_bounds) {
         Some(ref a_bnd) => {
             // If a has an upper bound, return the LUB(a.ub, b)
-            debug!("bnd=Some(%s)", a_bnd.inf_str(this.infcx()));
+            debug2!("bnd=Some({})", a_bnd.inf_str(this.infcx()));
             lattice_dir_op(a_bnd, b)
         }
         None => {
             // If a does not have an upper bound, make b the upper bound of a
             // and then return b.
-            debug!("bnd=None");
+            debug2!("bnd=None");
             let a_bounds = this.with_bnd(a_bounds, (*b).clone());
             do this.combine_fields().bnds(&a_bounds.lb, &a_bounds.ub).then {
                 this.infcx().set(a_id.clone(),
@@ -532,7 +532,7 @@ pub fn var_ids<T:Combine>(this: &T, isr: isr_alist) -> ~[RegionVid] {
             r => {
                 this.infcx().tcx.sess.span_bug(
                     this.trace().origin.span(),
-                    fmt!("Found non-region-vid: %?", r));
+                    format!("Found non-region-vid: {:?}", r));
             }
         }
         true
diff --git a/src/librustc/middle/typeck/infer/lub.rs b/src/librustc/middle/typeck/infer/lub.rs
index 260bc93611e..c8974a722fd 100644
--- a/src/librustc/middle/typeck/infer/lub.rs
+++ b/src/librustc/middle/typeck/infer/lub.rs
@@ -50,7 +50,7 @@ impl Combine for Lub {
     fn mts(&self, a: &ty::mt, b: &ty::mt) -> cres<ty::mt> {
         let tcx = self.infcx.tcx;
 
-        debug!("%s.mts(%s, %s)",
+        debug2!("{}.mts({}, {})",
                self.tag(),
                mt_to_str(tcx, a),
                mt_to_str(tcx, b));
@@ -106,7 +106,7 @@ impl Combine for Lub {
     }
 
     fn regions(&self, a: ty::Region, b: ty::Region) -> cres<ty::Region> {
-        debug!("%s.regions(%?, %?)",
+        debug2!("{}.regions({:?}, {:?})",
                self.tag(),
                a.inf_str(self.infcx),
                b.inf_str(self.infcx));
@@ -134,7 +134,7 @@ impl Combine for Lub {
 
         // Collect constraints.
         let sig0 = if_ok!(super_fn_sigs(self, &a_with_fresh, &b_with_fresh));
-        debug!("sig0 = %s", sig0.inf_str(self.infcx));
+        debug2!("sig0 = {}", sig0.inf_str(self.infcx));
 
         // Generalize the regions appearing in sig0 if possible
         let new_vars =
@@ -154,7 +154,7 @@ impl Combine for Lub {
                              r0: ty::Region) -> ty::Region {
             // Regions that pre-dated the LUB computation stay as they are.
             if !is_var_in_set(new_vars, r0) {
-                debug!("generalize_region(r0=%?): not new variable", r0);
+                debug2!("generalize_region(r0={:?}): not new variable", r0);
                 return r0;
             }
 
@@ -164,8 +164,8 @@ impl Combine for Lub {
             // *related* to regions that pre-date the LUB computation
             // stay as they are.
             if !tainted.iter().all(|r| is_var_in_set(new_vars, *r)) {
-                debug!("generalize_region(r0=%?): \
-                        non-new-variables found in %?",
+                debug2!("generalize_region(r0={:?}): \
+                        non-new-variables found in {:?}",
                        r0, tainted);
                 return r0;
             }
@@ -179,8 +179,8 @@ impl Combine for Lub {
             do list::each(a_isr) |pair| {
                 let (a_br, a_r) = *pair;
                 if tainted.iter().any(|x| x == &a_r) {
-                    debug!("generalize_region(r0=%?): \
-                            replacing with %?, tainted=%?",
+                    debug2!("generalize_region(r0={:?}): \
+                            replacing with {:?}, tainted={:?}",
                            r0, a_br, tainted);
                     ret = Some(ty::re_bound(a_br));
                     false
@@ -193,7 +193,7 @@ impl Combine for Lub {
                 Some(x) => x,
                 None => this.infcx.tcx.sess.span_bug(
                             this.trace.origin.span(),
-                            fmt!("Region %? is not associated with \
+                            format!("Region {:?} is not associated with \
                                   any bound region from A!", r0))
             }
         }
diff --git a/src/librustc/middle/typeck/infer/mod.rs b/src/librustc/middle/typeck/infer/mod.rs
index e73a36de143..89e9f626ca5 100644
--- a/src/librustc/middle/typeck/infer/mod.rs
+++ b/src/librustc/middle/typeck/infer/mod.rs
@@ -244,7 +244,7 @@ pub fn fixup_err_to_str(f: fixup_err) -> ~str {
       cyclic_ty(_) => ~"cyclic type of infinite size",
       unresolved_region(_) => ~"unconstrained region",
       region_var_bound_by_region_var(r1, r2) => {
-        fmt!("region var %? bound by another region var %?; this is \
+        format!("region var {:?} bound by another region var {:?}; this is \
               a bug in rustc", r1, r2)
       }
     }
@@ -285,7 +285,7 @@ pub fn common_supertype(cx: @mut InferCtxt,
      * not possible, reports an error and returns ty::err.
      */
 
-    debug!("common_supertype(%s, %s)", a.inf_str(cx), b.inf_str(cx));
+    debug2!("common_supertype({}, {})", a.inf_str(cx), b.inf_str(cx));
 
     let trace = TypeTrace {
         origin: origin,
@@ -311,7 +311,7 @@ pub fn mk_subty(cx: @mut InferCtxt,
                 a: ty::t,
                 b: ty::t)
              -> ures {
-    debug!("mk_subty(%s <: %s)", a.inf_str(cx), b.inf_str(cx));
+    debug2!("mk_subty({} <: {})", a.inf_str(cx), b.inf_str(cx));
     do indent {
         do cx.commit {
             let trace = TypeTrace {
@@ -324,7 +324,7 @@ pub fn mk_subty(cx: @mut InferCtxt,
 }
 
 pub fn can_mk_subty(cx: @mut InferCtxt, a: ty::t, b: ty::t) -> ures {
-    debug!("can_mk_subty(%s <: %s)", a.inf_str(cx), b.inf_str(cx));
+    debug2!("can_mk_subty({} <: {})", a.inf_str(cx), b.inf_str(cx));
     do indent {
         do cx.probe {
             let trace = TypeTrace {
@@ -341,7 +341,7 @@ pub fn mk_subr(cx: @mut InferCtxt,
                origin: SubregionOrigin,
                a: ty::Region,
                b: ty::Region) {
-    debug!("mk_subr(%s <: %s)", a.inf_str(cx), b.inf_str(cx));
+    debug2!("mk_subr({} <: {})", a.inf_str(cx), b.inf_str(cx));
     cx.region_vars.start_snapshot();
     cx.region_vars.make_subregion(origin, a, b);
     cx.region_vars.commit();
@@ -353,7 +353,7 @@ pub fn mk_eqty(cx: @mut InferCtxt,
                a: ty::t,
                b: ty::t)
             -> ures {
-    debug!("mk_eqty(%s <: %s)", a.inf_str(cx), b.inf_str(cx));
+    debug2!("mk_eqty({} <: {})", a.inf_str(cx), b.inf_str(cx));
     do indent {
         do cx.commit {
             let trace = TypeTrace {
@@ -373,7 +373,7 @@ pub fn mk_sub_trait_refs(cx: @mut InferCtxt,
                          b: @ty::TraitRef)
     -> ures
 {
-    debug!("mk_sub_trait_refs(%s <: %s)",
+    debug2!("mk_sub_trait_refs({} <: {})",
            a.inf_str(cx), b.inf_str(cx));
     do indent {
         do cx.commit {
@@ -403,7 +403,7 @@ pub fn mk_coercety(cx: @mut InferCtxt,
                    a: ty::t,
                    b: ty::t)
                 -> CoerceResult {
-    debug!("mk_coercety(%s -> %s)", a.inf_str(cx), b.inf_str(cx));
+    debug2!("mk_coercety({} -> {})", a.inf_str(cx), b.inf_str(cx));
     do indent {
         do cx.commit {
             let trace = TypeTrace {
@@ -416,7 +416,7 @@ pub fn mk_coercety(cx: @mut InferCtxt,
 }
 
 pub fn can_mk_coercety(cx: @mut InferCtxt, a: ty::t, b: ty::t) -> ures {
-    debug!("can_mk_coercety(%s -> %s)", a.inf_str(cx), b.inf_str(cx));
+    debug2!("can_mk_coercety({} -> {})", a.inf_str(cx), b.inf_str(cx));
     do indent {
         do cx.probe {
             let trace = TypeTrace {
@@ -539,7 +539,7 @@ impl InferCtxt {
     }
 
     pub fn rollback_to(&mut self, snapshot: &Snapshot) {
-        debug!("rollback!");
+        debug2!("rollback!");
         rollback_to(&mut self.ty_var_bindings, snapshot.ty_var_bindings_len);
 
         rollback_to(&mut self.int_var_bindings,
@@ -554,7 +554,7 @@ impl InferCtxt {
     pub fn commit<T,E>(@mut self, f: &fn() -> Result<T,E>) -> Result<T,E> {
         assert!(!self.in_snapshot());
 
-        debug!("commit()");
+        debug2!("commit()");
         do indent {
             let r = self.try(|| f());
 
@@ -567,7 +567,7 @@ impl InferCtxt {
 
     /// Execute `f`, unroll bindings on failure
     pub fn try<T,E>(@mut self, f: &fn() -> Result<T,E>) -> Result<T,E> {
-        debug!("try()");
+        debug2!("try()");
         do indent {
             let snapshot = self.start_snapshot();
             let r = f();
@@ -581,7 +581,7 @@ impl InferCtxt {
 
     /// Execute `f` then unroll any bindings it creates
     pub fn probe<T,E>(@mut self, f: &fn() -> Result<T,E>) -> Result<T,E> {
-        debug!("probe()");
+        debug2!("probe()");
         do indent {
             let snapshot = self.start_snapshot();
             let r = f();
@@ -654,7 +654,7 @@ impl InferCtxt {
 
     pub fn tys_to_str(@mut self, ts: &[ty::t]) -> ~str {
         let tstrs = ts.map(|t| self.ty_to_str(*t));
-        fmt!("(%s)", tstrs.connect(", "))
+        format!("({})", tstrs.connect(", "))
     }
 
     pub fn trait_ref_to_str(@mut self, t: &ty::TraitRef) -> ~str {
@@ -690,8 +690,8 @@ impl InferCtxt {
             }
             _ => {
                 self.tcx.sess.bug(
-                    fmt!("resolve_type_vars_if_possible() yielded %s \
-                          when supplied with %s",
+                    format!("resolve_type_vars_if_possible() yielded {} \
+                          when supplied with {}",
                          self.ty_to_str(dummy0),
                          self.ty_to_str(dummy1)));
             }
@@ -725,10 +725,10 @@ impl InferCtxt {
                                                 expected_ty: Option<ty::t>,
                                                 actual_ty: ~str,
                                                 err: Option<&ty::type_err>) {
-        debug!("hi! expected_ty = %?, actual_ty = %s", expected_ty, actual_ty);
+        debug2!("hi! expected_ty = {:?}, actual_ty = {}", expected_ty, actual_ty);
 
         let error_str = do err.map_move_default(~"") |t_err| {
-            fmt!(" (%s)", ty::type_err_to_str(self.tcx, t_err))
+            format!(" ({})", ty::type_err_to_str(self.tcx, t_err))
         };
         let resolved_expected = do expected_ty.map_move |e_ty| {
             self.resolve_type_vars_if_possible(e_ty)
@@ -736,10 +736,10 @@ impl InferCtxt {
         if !resolved_expected.map_move_default(false, |e| { ty::type_is_error(e) }) {
             match resolved_expected {
                 None => self.tcx.sess.span_err(sp,
-                            fmt!("%s%s", mk_msg(None, actual_ty), error_str)),
+                            format!("{}{}", mk_msg(None, actual_ty), error_str)),
                 Some(e) => {
                     self.tcx.sess.span_err(sp,
-                        fmt!("%s%s", mk_msg(Some(self.ty_to_str(e)), actual_ty), error_str));
+                        format!("{}{}", mk_msg(Some(self.ty_to_str(e)), actual_ty), error_str));
                 }
             }
             for err in err.iter() {
@@ -776,7 +776,7 @@ impl InferCtxt {
             _ => {
                 // if I leave out : ~str, it infers &str and complains
                 |actual: ~str| {
-                    fmt!("mismatched types: expected `%s` but found `%s`",
+                    format!("mismatched types: expected `{}` but found `{}`",
                          self.ty_to_str(resolved_expected), actual)
                 }
             }
@@ -792,7 +792,7 @@ impl InferCtxt {
             replace_bound_regions_in_fn_sig(self.tcx, @Nil, None, fsig, |br| {
                 let rvar = self.next_region_var(
                     BoundRegionInFnType(trace.origin.span(), br));
-                debug!("Bound region %s maps to %?",
+                debug2!("Bound region {} maps to {:?}",
                        bound_region_to_str(self.tcx, "", false, br),
                        rvar);
                 rvar
@@ -819,7 +819,7 @@ impl TypeTrace {
 
 impl Repr for TypeTrace {
     fn repr(&self, tcx: ty::ctxt) -> ~str {
-        fmt!("TypeTrace(%s)", self.origin.repr(tcx))
+        format!("TypeTrace({})", self.origin.repr(tcx))
     }
 }
 
@@ -840,13 +840,13 @@ impl TypeOrigin {
 impl Repr for TypeOrigin {
     fn repr(&self, tcx: ty::ctxt) -> ~str {
         match *self {
-            MethodCompatCheck(a) => fmt!("MethodCompatCheck(%s)", a.repr(tcx)),
-            ExprAssignable(a) => fmt!("ExprAssignable(%s)", a.repr(tcx)),
-            Misc(a) => fmt!("Misc(%s)", a.repr(tcx)),
-            RelateTraitRefs(a) => fmt!("RelateTraitRefs(%s)", a.repr(tcx)),
-            RelateSelfType(a) => fmt!("RelateSelfType(%s)", a.repr(tcx)),
-            MatchExpression(a) => fmt!("MatchExpression(%s)", a.repr(tcx)),
-            IfExpression(a) => fmt!("IfExpression(%s)", a.repr(tcx)),
+            MethodCompatCheck(a) => format!("MethodCompatCheck({})", a.repr(tcx)),
+            ExprAssignable(a) => format!("ExprAssignable({})", a.repr(tcx)),
+            Misc(a) => format!("Misc({})", a.repr(tcx)),
+            RelateTraitRefs(a) => format!("RelateTraitRefs({})", a.repr(tcx)),
+            RelateSelfType(a) => format!("RelateSelfType({})", a.repr(tcx)),
+            MatchExpression(a) => format!("MatchExpression({})", a.repr(tcx)),
+            IfExpression(a) => format!("IfExpression({})", a.repr(tcx)),
         }
     }
 }
@@ -876,21 +876,23 @@ impl SubregionOrigin {
 impl Repr for SubregionOrigin {
     fn repr(&self, tcx: ty::ctxt) -> ~str {
         match *self {
-            Subtype(a) => fmt!("Subtype(%s)", a.repr(tcx)),
-            InfStackClosure(a) => fmt!("InfStackClosure(%s)", a.repr(tcx)),
-            InvokeClosure(a) => fmt!("InvokeClosure(%s)", a.repr(tcx)),
-            DerefPointer(a) => fmt!("DerefPointer(%s)", a.repr(tcx)),
-            FreeVariable(a) => fmt!("FreeVariable(%s)", a.repr(tcx)),
-            IndexSlice(a) => fmt!("IndexSlice(%s)", a.repr(tcx)),
-            RelateObjectBound(a) => fmt!("RelateObjectBound(%s)", a.repr(tcx)),
-            Reborrow(a) => fmt!("Reborrow(%s)", a.repr(tcx)),
-            ReferenceOutlivesReferent(_, a) => fmt!("ReferenceOutlivesReferent(%s)", a.repr(tcx)),
-            BindingTypeIsNotValidAtDecl(a) => fmt!("BindingTypeIsNotValidAtDecl(%s)", a.repr(tcx)),
-            CallRcvr(a) => fmt!("CallRcvr(%s)", a.repr(tcx)),
-            CallArg(a) => fmt!("CallArg(%s)", a.repr(tcx)),
-            CallReturn(a) => fmt!("CallReturn(%s)", a.repr(tcx)),
-            AddrOf(a) => fmt!("AddrOf(%s)", a.repr(tcx)),
-            AutoBorrow(a) => fmt!("AutoBorrow(%s)", a.repr(tcx)),
+            Subtype(a) => format!("Subtype({})", a.repr(tcx)),
+            InfStackClosure(a) => format!("InfStackClosure({})", a.repr(tcx)),
+            InvokeClosure(a) => format!("InvokeClosure({})", a.repr(tcx)),
+            DerefPointer(a) => format!("DerefPointer({})", a.repr(tcx)),
+            FreeVariable(a) => format!("FreeVariable({})", a.repr(tcx)),
+            IndexSlice(a) => format!("IndexSlice({})", a.repr(tcx)),
+            RelateObjectBound(a) => format!("RelateObjectBound({})", a.repr(tcx)),
+            Reborrow(a) => format!("Reborrow({})", a.repr(tcx)),
+            ReferenceOutlivesReferent(_, a) =>
+                format!("ReferenceOutlivesReferent({})", a.repr(tcx)),
+            BindingTypeIsNotValidAtDecl(a) =>
+                format!("BindingTypeIsNotValidAtDecl({})", a.repr(tcx)),
+            CallRcvr(a) => format!("CallRcvr({})", a.repr(tcx)),
+            CallArg(a) => format!("CallArg({})", a.repr(tcx)),
+            CallReturn(a) => format!("CallReturn({})", a.repr(tcx)),
+            AddrOf(a) => format!("AddrOf({})", a.repr(tcx)),
+            AutoBorrow(a) => format!("AutoBorrow({})", a.repr(tcx)),
         }
     }
 }
@@ -916,20 +918,20 @@ impl RegionVariableOrigin {
 impl Repr for RegionVariableOrigin {
     fn repr(&self, tcx: ty::ctxt) -> ~str {
         match *self {
-            MiscVariable(a) => fmt!("MiscVariable(%s)", a.repr(tcx)),
-            PatternRegion(a) => fmt!("PatternRegion(%s)", a.repr(tcx)),
-            AddrOfRegion(a) => fmt!("AddrOfRegion(%s)", a.repr(tcx)),
-            AddrOfSlice(a) => fmt!("AddrOfSlice(%s)", a.repr(tcx)),
-            Autoref(a) => fmt!("Autoref(%s)", a.repr(tcx)),
-            Coercion(a) => fmt!("Coercion(%s)", a.repr(tcx)),
-            BoundRegionInFnCall(a, b) => fmt!("BoundRegionInFnCall(%s,%s)",
+            MiscVariable(a) => format!("MiscVariable({})", a.repr(tcx)),
+            PatternRegion(a) => format!("PatternRegion({})", a.repr(tcx)),
+            AddrOfRegion(a) => format!("AddrOfRegion({})", a.repr(tcx)),
+            AddrOfSlice(a) => format!("AddrOfSlice({})", a.repr(tcx)),
+            Autoref(a) => format!("Autoref({})", a.repr(tcx)),
+            Coercion(a) => format!("Coercion({})", a.repr(tcx)),
+            BoundRegionInFnCall(a, b) => format!("BoundRegionInFnCall({},{})",
                                               a.repr(tcx), b.repr(tcx)),
-            BoundRegionInFnType(a, b) => fmt!("BoundRegionInFnType(%s,%s)",
+            BoundRegionInFnType(a, b) => format!("BoundRegionInFnType({},{})",
                                               a.repr(tcx), b.repr(tcx)),
-            BoundRegionInTypeOrImpl(a) => fmt!("BoundRegionInTypeOrImpl(%s)",
+            BoundRegionInTypeOrImpl(a) => format!("BoundRegionInTypeOrImpl({})",
                                                a.repr(tcx)),
-            BoundRegionInCoherence => fmt!("BoundRegionInCoherence"),
-            BoundRegionError(a) => fmt!("BoundRegionError(%s)", a.repr(tcx)),
+            BoundRegionInCoherence => format!("BoundRegionInCoherence"),
+            BoundRegionError(a) => format!("BoundRegionError({})", a.repr(tcx)),
         }
     }
 }
diff --git a/src/librustc/middle/typeck/infer/region_inference/mod.rs b/src/librustc/middle/typeck/infer/region_inference/mod.rs
index c14e49f37e5..e5492453b98 100644
--- a/src/librustc/middle/typeck/infer/region_inference/mod.rs
+++ b/src/librustc/middle/typeck/infer/region_inference/mod.rs
@@ -130,7 +130,7 @@ impl RegionVarBindings {
     }
 
     pub fn start_snapshot(&mut self) -> uint {
-        debug!("RegionVarBindings: snapshot()=%u", self.undo_log.len());
+        debug2!("RegionVarBindings: snapshot()={}", self.undo_log.len());
         if self.in_snapshot() {
             self.undo_log.len()
         } else {
@@ -140,17 +140,17 @@ impl RegionVarBindings {
     }
 
     pub fn commit(&mut self) {
-        debug!("RegionVarBindings: commit()");
+        debug2!("RegionVarBindings: commit()");
         while self.undo_log.len() > 0 {
             self.undo_log.pop();
         }
     }
 
     pub fn rollback_to(&mut self, snapshot: uint) {
-        debug!("RegionVarBindings: rollback_to(%u)", snapshot);
+        debug2!("RegionVarBindings: rollback_to({})", snapshot);
         while self.undo_log.len() > snapshot {
             let undo_item = self.undo_log.pop();
-            debug!("undo_item=%?", undo_item);
+            debug2!("undo_item={:?}", undo_item);
             match undo_item {
               Snapshot => {}
               AddVar(vid) => {
@@ -181,7 +181,7 @@ impl RegionVarBindings {
         if self.in_snapshot() {
             self.undo_log.push(AddVar(vid));
         }
-        debug!("created new region variable %? with origin %?",
+        debug2!("created new region variable {:?} with origin {:?}",
                vid, origin.repr(self.tcx));
         return vid;
     }
@@ -218,7 +218,7 @@ impl RegionVarBindings {
         // cannot add constraints once regions are resolved
         assert!(self.values.is_empty());
 
-        debug!("RegionVarBindings: add_constraint(%?)", constraint);
+        debug2!("RegionVarBindings: add_constraint({:?})", constraint);
 
         if self.constraints.insert(constraint, origin) {
             if self.in_snapshot() {
@@ -234,7 +234,7 @@ impl RegionVarBindings {
         // cannot add constraints once regions are resolved
         assert!(self.values.is_empty());
 
-        debug!("RegionVarBindings: make_subregion(%?, %?)", sub, sup);
+        debug2!("RegionVarBindings: make_subregion({:?}, {:?})", sub, sup);
         match (sub, sup) {
           (re_infer(ReVar(sub_id)), re_infer(ReVar(sup_id))) => {
             self.add_constraint(ConstrainVarSubVar(sub_id, sup_id), origin);
@@ -248,12 +248,12 @@ impl RegionVarBindings {
           (re_bound(br), _) => {
             self.tcx.sess.span_bug(
                 origin.span(),
-                fmt!("Cannot relate bound region as subregion: %?", br));
+                format!("Cannot relate bound region as subregion: {:?}", br));
           }
           (_, re_bound(br)) => {
             self.tcx.sess.span_bug(
                 origin.span(),
-                fmt!("Cannot relate bound region as superregion: %?", br));
+                format!("Cannot relate bound region as superregion: {:?}", br));
           }
           _ => {
             self.add_constraint(ConstrainRegSubReg(sub, sup), origin);
@@ -269,7 +269,7 @@ impl RegionVarBindings {
         // cannot add constraints once regions are resolved
         assert!(self.values.is_empty());
 
-        debug!("RegionVarBindings: lub_regions(%?, %?)", a, b);
+        debug2!("RegionVarBindings: lub_regions({:?}, {:?})", a, b);
         match (a, b) {
             (re_static, _) | (_, re_static) => {
                 re_static // nothing lives longer than static
@@ -292,7 +292,7 @@ impl RegionVarBindings {
         // cannot add constraints once regions are resolved
         assert!(self.values.is_empty());
 
-        debug!("RegionVarBindings: glb_regions(%?, %?)", a, b);
+        debug2!("RegionVarBindings: glb_regions({:?}, {:?})", a, b);
         match (a, b) {
             (re_static, r) | (r, re_static) => {
                 // static lives longer than everything else
@@ -312,12 +312,12 @@ impl RegionVarBindings {
         if self.values.is_empty() {
             self.tcx.sess.span_bug(
                 self.var_origins[rid.to_uint()].span(),
-                fmt!("Attempt to resolve region variable before values have \
+                format!("Attempt to resolve region variable before values have \
                       been computed!"));
         }
 
         let v = self.values.with_ref(|values| values[rid.to_uint()]);
-        debug!("RegionVarBindings: resolve_var(%?=%u)=%?",
+        debug2!("RegionVarBindings: resolve_var({:?}={})={:?}",
                rid, rid.to_uint(), v);
         match v {
             Value(r) => r,
@@ -367,7 +367,7 @@ impl RegionVarBindings {
         }
         relate(self, a, re_infer(ReVar(c)));
         relate(self, b, re_infer(ReVar(c)));
-        debug!("combine_vars() c=%?", c);
+        debug2!("combine_vars() c={:?}", c);
         re_infer(ReVar(c))
     }
 
@@ -390,7 +390,7 @@ impl RegionVarBindings {
          * regions.
          */
 
-        debug!("tainted(snapshot=%u, r0=%?)", snapshot, r0);
+        debug2!("tainted(snapshot={}, r0={:?})", snapshot, r0);
         let _indenter = indenter();
 
         let undo_len = self.undo_log.len();
@@ -404,7 +404,7 @@ impl RegionVarBindings {
             // nb: can't use uint::range() here because result_set grows
             let r = result_set[result_index];
 
-            debug!("result_index=%u, r=%?", result_index, r);
+            debug2!("result_index={}, r={:?}", result_index, r);
 
             let mut undo_index = snapshot;
             while undo_index < undo_len {
@@ -469,7 +469,7 @@ impl RegionVarBindings {
     errors are reported.
     */
     pub fn resolve_regions(&mut self) -> OptVec<RegionResolutionError> {
-        debug!("RegionVarBindings: resolve_regions()");
+        debug2!("RegionVarBindings: resolve_regions()");
         let mut errors = opt_vec::Empty;
         let v = self.infer_variable_values(&mut errors);
         self.values.put_back(v);
@@ -496,8 +496,8 @@ impl RegionVarBindings {
           (re_infer(ReVar(v_id)), _) | (_, re_infer(ReVar(v_id))) => {
             self.tcx.sess.span_bug(
                 self.var_origins[v_id.to_uint()].span(),
-                fmt!("lub_concrete_regions invoked with \
-                      non-concrete regions: %?, %?", a, b));
+                format!("lub_concrete_regions invoked with \
+                      non-concrete regions: {:?}, {:?}", a, b));
           }
 
           (f @ re_free(ref fr), re_scope(s_id)) |
@@ -582,7 +582,7 @@ impl RegionVarBindings {
                             a: Region,
                             b: Region)
                          -> cres<Region> {
-        debug!("glb_concrete_regions(%?, %?)", a, b);
+        debug2!("glb_concrete_regions({:?}, {:?})", a, b);
         match (a, b) {
             (re_static, r) | (r, re_static) => {
                 // static lives longer than everything else
@@ -598,8 +598,8 @@ impl RegionVarBindings {
             (_, re_infer(ReVar(v_id))) => {
                 self.tcx.sess.span_bug(
                     self.var_origins[v_id.to_uint()].span(),
-                    fmt!("glb_concrete_regions invoked with \
-                          non-concrete regions: %?, %?", a, b));
+                    format!("glb_concrete_regions invoked with \
+                          non-concrete regions: {:?}, {:?}", a, b));
             }
 
             (re_free(ref fr), s @ re_scope(s_id)) |
@@ -691,7 +691,7 @@ impl RegionVarBindings {
         // scopes or two free regions.  So, if one of
         // these scopes is a subscope of the other, return
         // it.  Otherwise fail.
-        debug!("intersect_scopes(scope_a=%?, scope_b=%?, region_a=%?, region_b=%?)",
+        debug2!("intersect_scopes(scope_a={:?}, scope_b={:?}, region_a={:?}, region_b={:?})",
                scope_a, scope_b, region_a, region_b);
         let rm = self.tcx.region_maps;
         match rm.nearest_common_ancestor(scope_a, scope_b) {
@@ -778,13 +778,13 @@ impl RegionVarBindings {
                    b_vid: RegionVid,
                    b_data: &mut VarData)
                    -> bool {
-        debug!("expand_node(%?, %? == %?)",
+        debug2!("expand_node({:?}, {:?} == {:?})",
                a_region, b_vid, b_data.value);
 
         b_data.classification = Expanding;
         match b_data.value {
           NoValue => {
-            debug!("Setting initial value of %? to %?", b_vid, a_region);
+            debug2!("Setting initial value of {:?} to {:?}", b_vid, a_region);
 
             b_data.value = Value(a_region);
             return true;
@@ -796,7 +796,7 @@ impl RegionVarBindings {
                 return false;
             }
 
-            debug!("Expanding value of %? from %? to %?",
+            debug2!("Expanding value of {:?} from {:?} to {:?}",
                    b_vid, cur_region, lub);
 
             b_data.value = Value(lub);
@@ -843,7 +843,7 @@ impl RegionVarBindings {
                      a_data: &mut VarData,
                      b_region: Region)
                      -> bool {
-        debug!("contract_node(%? == %?/%?, %?)",
+        debug2!("contract_node({:?} == {:?}/{:?}, {:?})",
                a_vid, a_data.value, a_data.classification, b_region);
 
         return match a_data.value {
@@ -876,7 +876,7 @@ impl RegionVarBindings {
                       b_region: Region)
                    -> bool {
             if !this.is_subregion_of(a_region, b_region) {
-                debug!("Setting %? to ErrorValue: %? not subregion of %?",
+                debug2!("Setting {:?} to ErrorValue: {:?} not subregion of {:?}",
                        a_vid, a_region, b_region);
                 a_data.value = ErrorValue;
             }
@@ -894,14 +894,14 @@ impl RegionVarBindings {
                     if glb == a_region {
                         false
                     } else {
-                        debug!("Contracting value of %? from %? to %?",
+                        debug2!("Contracting value of {:?} from {:?} to {:?}",
                                a_vid, a_region, glb);
                         a_data.value = Value(glb);
                         true
                     }
                 }
                 Err(_) => {
-                    debug!("Setting %? to ErrorValue: no glb of %?, %?",
+                    debug2!("Setting {:?} to ErrorValue: no glb of {:?}, {:?}",
                            a_vid, a_region, b_region);
                     a_data.value = ErrorValue;
                     false
@@ -930,7 +930,7 @@ impl RegionVarBindings {
                 loop;
             }
 
-            debug!("ConcreteFailure: !(sub <= sup): sub=%?, sup=%?",
+            debug2!("ConcreteFailure: !(sub <= sup): sub={:?}, sup={:?}",
                    sub, sup);
             let origin = self.constraints.get_copy(constraint);
             errors.push(ConcreteFailure(origin, sub, sup));
@@ -943,7 +943,7 @@ impl RegionVarBindings {
         errors: &mut OptVec<RegionResolutionError>)
         -> ~[VarValue]
     {
-        debug!("extract_values_and_collect_conflicts()");
+        debug2!("extract_values_and_collect_conflicts()");
 
         // This is the best way that I have found to suppress
         // duplicate and related errors. Basically we keep a set of
@@ -1095,8 +1095,8 @@ impl RegionVarBindings {
 
         self.tcx.sess.span_bug(
             self.var_origins[node_idx.to_uint()].span(),
-            fmt!("collect_error_for_expanding_node() could not find error \
-                  for var %?, lower_bounds=%s, upper_bounds=%s",
+            format!("collect_error_for_expanding_node() could not find error \
+                  for var {:?}, lower_bounds={}, upper_bounds={}",
                  node_idx,
                  lower_bounds.map(|x| x.region).repr(self.tcx),
                  upper_bounds.map(|x| x.region).repr(self.tcx)));
@@ -1140,8 +1140,8 @@ impl RegionVarBindings {
 
         self.tcx.sess.span_bug(
             self.var_origins[node_idx.to_uint()].span(),
-            fmt!("collect_error_for_contracting_node() could not find error \
-                  for var %?, upper_bounds=%s",
+            format!("collect_error_for_contracting_node() could not find error \
+                  for var {:?}, upper_bounds={}",
                  node_idx,
                  upper_bounds.map(|x| x.region).repr(self.tcx)));
     }
@@ -1182,8 +1182,8 @@ impl RegionVarBindings {
                 state.dup_found = true;
             }
 
-            debug!("collect_concrete_regions(orig_node_idx=%?, node_idx=%?, \
-                    classification=%?)",
+            debug2!("collect_concrete_regions(orig_node_idx={:?}, node_idx={:?}, \
+                    classification={:?})",
                    orig_node_idx, node_idx, classification);
 
             // figure out the direction from which this node takes its
@@ -1204,7 +1204,7 @@ impl RegionVarBindings {
                          graph: &RegionGraph,
                          source_vid: RegionVid,
                          dir: Direction) {
-            debug!("process_edges(source_vid=%?, dir=%?)", source_vid, dir);
+            debug2!("process_edges(source_vid={:?}, dir={:?})", source_vid, dir);
 
             let source_node_index = NodeIndex(source_vid.to_uint());
             do graph.each_adjacent_edge(source_node_index, dir) |_, edge| {
@@ -1240,17 +1240,17 @@ impl RegionVarBindings {
         while changed {
             changed = false;
             iteration += 1;
-            debug!("---- %s Iteration #%u", tag, iteration);
+            debug2!("---- {} Iteration \\#{}", tag, iteration);
             for (constraint, _) in self.constraints.iter() {
                 let edge_changed = body(constraint);
                 if edge_changed {
-                    debug!("Updated due to constraint %s",
+                    debug2!("Updated due to constraint {}",
                            constraint.repr(self.tcx));
                     changed = true;
                 }
             }
         }
-        debug!("---- %s Complete after %u iteration(s)", tag, iteration);
+        debug2!("---- {} Complete after {} iteration(s)", tag, iteration);
     }
 
 }
@@ -1258,13 +1258,13 @@ impl RegionVarBindings {
 impl Repr for Constraint {
     fn repr(&self, tcx: ty::ctxt) -> ~str {
         match *self {
-            ConstrainVarSubVar(a, b) => fmt!("ConstrainVarSubVar(%s, %s)",
+            ConstrainVarSubVar(a, b) => format!("ConstrainVarSubVar({}, {})",
                                              a.repr(tcx), b.repr(tcx)),
-            ConstrainRegSubVar(a, b) => fmt!("ConstrainRegSubVar(%s, %s)",
+            ConstrainRegSubVar(a, b) => format!("ConstrainRegSubVar({}, {})",
                                              a.repr(tcx), b.repr(tcx)),
-            ConstrainVarSubReg(a, b) => fmt!("ConstrainVarSubReg(%s, %s)",
+            ConstrainVarSubReg(a, b) => format!("ConstrainVarSubReg({}, {})",
                                              a.repr(tcx), b.repr(tcx)),
-            ConstrainRegSubReg(a, b) => fmt!("ConstrainRegSubReg(%s, %s)",
+            ConstrainRegSubReg(a, b) => format!("ConstrainRegSubReg({}, {})",
                                              a.repr(tcx), b.repr(tcx)),
         }
     }
diff --git a/src/librustc/middle/typeck/infer/resolve.rs b/src/librustc/middle/typeck/infer/resolve.rs
index 941431ce0e3..57e0ecf8745 100644
--- a/src/librustc/middle/typeck/infer/resolve.rs
+++ b/src/librustc/middle/typeck/infer/resolve.rs
@@ -104,7 +104,7 @@ impl ResolveState {
     pub fn resolve_type_chk(&mut self, typ: ty::t) -> fres<ty::t> {
         self.err = None;
 
-        debug!("Resolving %s (modes=%x)",
+        debug2!("Resolving {} (modes={:x})",
                ty_to_str(self.infcx.tcx, typ),
                self.modes);
 
@@ -116,7 +116,7 @@ impl ResolveState {
         assert!(self.v_seen.is_empty());
         match self.err {
           None => {
-            debug!("Resolved to %s + %s (modes=%x)",
+            debug2!("Resolved to {} + {} (modes={:x})",
                    ty_to_str(self.infcx.tcx, rty),
                    ty_to_str(self.infcx.tcx, rty),
                    self.modes);
@@ -137,7 +137,7 @@ impl ResolveState {
     }
 
     pub fn resolve_type(&mut self, typ: ty::t) -> ty::t {
-        debug!("resolve_type(%s)", typ.inf_str(self.infcx));
+        debug2!("resolve_type({})", typ.inf_str(self.infcx));
         let _i = indenter();
 
         if !ty::type_needs_infer(typ) {
@@ -179,7 +179,7 @@ impl ResolveState {
     }
 
     pub fn resolve_region(&mut self, orig: ty::Region) -> ty::Region {
-        debug!("Resolve_region(%s)", orig.inf_str(self.infcx));
+        debug2!("Resolve_region({})", orig.inf_str(self.infcx));
         match orig {
           ty::re_infer(ty::ReVar(rid)) => self.resolve_region_var(rid),
           _ => orig
diff --git a/src/librustc/middle/typeck/infer/sub.rs b/src/librustc/middle/typeck/infer/sub.rs
index 57ebb2185d1..ad251a5be9e 100644
--- a/src/librustc/middle/typeck/infer/sub.rs
+++ b/src/librustc/middle/typeck/infer/sub.rs
@@ -56,7 +56,7 @@ impl Combine for Sub {
     }
 
     fn regions(&self, a: ty::Region, b: ty::Region) -> cres<ty::Region> {
-        debug!("%s.regions(%s, %s)",
+        debug2!("{}.regions({}, {})",
                self.tag(),
                a.inf_str(self.infcx),
                b.inf_str(self.infcx));
@@ -65,7 +65,7 @@ impl Combine for Sub {
     }
 
     fn mts(&self, a: &ty::mt, b: &ty::mt) -> cres<ty::mt> {
-        debug!("mts(%s <: %s)", a.inf_str(self.infcx), b.inf_str(self.infcx));
+        debug2!("mts({} <: {})", a.inf_str(self.infcx), b.inf_str(self.infcx));
 
         if a.mutbl != b.mutbl {
             return Err(ty::terr_mutability);
@@ -110,7 +110,7 @@ impl Combine for Sub {
     }
 
     fn tys(&self, a: ty::t, b: ty::t) -> cres<ty::t> {
-        debug!("%s.tys(%s, %s)", self.tag(),
+        debug2!("{}.tys({}, {})", self.tag(),
                a.inf_str(self.infcx), b.inf_str(self.infcx));
         if a == b { return Ok(a); }
         let _indenter = indenter();
@@ -143,7 +143,7 @@ impl Combine for Sub {
     }
 
     fn fn_sigs(&self, a: &ty::FnSig, b: &ty::FnSig) -> cres<ty::FnSig> {
-        debug!("fn_sigs(a=%s, b=%s)",
+        debug2!("fn_sigs(a={}, b={})",
                a.inf_str(self.infcx), b.inf_str(self.infcx));
         let _indenter = indenter();
 
@@ -172,15 +172,15 @@ impl Combine for Sub {
             do replace_bound_regions_in_fn_sig(self.infcx.tcx, @Nil,
                                               None, b) |br| {
                 let skol = self.infcx.region_vars.new_skolemized(br);
-                debug!("Bound region %s skolemized to %?",
+                debug2!("Bound region {} skolemized to {:?}",
                        bound_region_to_str(self.infcx.tcx, "", false, br),
                        skol);
                 skol
             }
         };
 
-        debug!("a_sig=%s", a_sig.inf_str(self.infcx));
-        debug!("b_sig=%s", b_sig.inf_str(self.infcx));
+        debug2!("a_sig={}", a_sig.inf_str(self.infcx));
+        debug2!("b_sig={}", b_sig.inf_str(self.infcx));
 
         // Compare types now that bound regions have been replaced.
         let sig = if_ok!(super_fn_sigs(self, &a_sig, &b_sig));
diff --git a/src/librustc/middle/typeck/infer/test.rs b/src/librustc/middle/typeck/infer/test.rs
index 3aeea2bcc3b..8792a068671 100644
--- a/src/librustc/middle/typeck/infer/test.rs
+++ b/src/librustc/middle/typeck/infer/test.rs
@@ -100,7 +100,7 @@ impl Env {
         return match search_mod(self, &self.crate.node.module, 0, names) {
             Some(id) => id,
             None => {
-                fail!("No item found: `%s`", names.connect("::"));
+                fail2!("No item found: `%s`", names.connect("::"));
             }
         };
 
@@ -153,7 +153,7 @@ impl Env {
 
     pub fn assert_subtype(&self, a: ty::t, b: ty::t) {
         if !self.is_subtype(a, b) {
-            fail!("%s is not a subtype of %s, but it should be",
+            fail2!("%s is not a subtype of %s, but it should be",
                   self.ty_to_str(a),
                   self.ty_to_str(b));
         }
@@ -161,7 +161,7 @@ impl Env {
 
     pub fn assert_not_subtype(&self, a: ty::t, b: ty::t) {
         if self.is_subtype(a, b) {
-            fail!("%s is a subtype of %s, but it shouldn't be",
+            fail2!("%s is a subtype of %s, but it shouldn't be",
                   self.ty_to_str(a),
                   self.ty_to_str(b));
         }
@@ -223,14 +223,14 @@ impl Env {
     pub fn glb() -> Glb { Glb(self.infcx.combine_fields(true, dummy_sp())) }
 
     pub fn resolve_regions(exp_count: uint) {
-        debug!("resolve_regions(%u)", exp_count);
+        debug2!("resolve_regions(%u)", exp_count);
 
         self.infcx.resolve_regions();
         if self.err_messages.len() != exp_count {
             for msg in self.err_messages.iter() {
-                debug!("Error encountered: %s", *msg);
+                debug2!("Error encountered: %s", *msg);
             }
-            fmt!("Resolving regions encountered %u errors but expected %u!",
+            format!("Resolving regions encountered %u errors but expected %u!",
                  self.err_messages.len(),
                  exp_count);
         }
@@ -240,7 +240,7 @@ impl Env {
     pub fn check_lub(&self, t1: ty::t, t2: ty::t, t_lub: ty::t) {
         match self.lub().tys(t1, t2) {
             Err(e) => {
-                fail!("Unexpected error computing LUB: %?", e)
+                fail2!("Unexpected error computing LUB: %?", e)
             }
             Ok(t) => {
                 self.assert_eq(t, t_lub);
@@ -256,13 +256,13 @@ impl Env {
 
     /// Checks that `GLB(t1,t2) == t_glb`
     pub fn check_glb(&self, t1: ty::t, t2: ty::t, t_glb: ty::t) {
-        debug!("check_glb(t1=%s, t2=%s, t_glb=%s)",
+        debug2!("check_glb(t1=%s, t2=%s, t_glb=%s)",
                self.ty_to_str(t1),
                self.ty_to_str(t2),
                self.ty_to_str(t_glb));
         match self.glb().tys(t1, t2) {
             Err(e) => {
-                fail!("Unexpected error computing LUB: %?", e)
+                fail2!("Unexpected error computing LUB: %?", e)
             }
             Ok(t) => {
                 self.assert_eq(t, t_glb);
@@ -281,7 +281,7 @@ impl Env {
         match self.lub().tys(t1, t2) {
             Err(_) => {}
             Ok(t) => {
-                fail!("Unexpected success computing LUB: %?", self.ty_to_str(t))
+                fail2!("Unexpected success computing LUB: %?", self.ty_to_str(t))
             }
         }
     }
@@ -291,7 +291,7 @@ impl Env {
         match self.glb().tys(t1, t2) {
             Err(_) => {}
             Ok(t) => {
-                fail!("Unexpected success computing GLB: %?", self.ty_to_str(t))
+                fail2!("Unexpected success computing GLB: %?", self.ty_to_str(t))
             }
         }
     }
diff --git a/src/librustc/middle/typeck/infer/to_str.rs b/src/librustc/middle/typeck/infer/to_str.rs
index e2d6d588bae..2bb7a994593 100644
--- a/src/librustc/middle/typeck/infer/to_str.rs
+++ b/src/librustc/middle/typeck/infer/to_str.rs
@@ -31,7 +31,7 @@ impl InferStr for ty::t {
 
 impl InferStr for FnSig {
     fn inf_str(&self, cx: &InferCtxt) -> ~str {
-        fmt!("(%s) -> %s",
+        format!("({}) -> {}",
              self.inputs.map(|a| a.inf_str(cx)).connect(", "),
              self.output.inf_str(cx))
     }
@@ -45,7 +45,7 @@ impl InferStr for ty::mt {
 
 impl InferStr for ty::Region {
     fn inf_str(&self, _cx: &InferCtxt) -> ~str {
-        fmt!("%?", *self)
+        format!("{:?}", *self)
     }
 }
 
@@ -60,7 +60,7 @@ impl<V:InferStr> InferStr for Bound<V> {
 
 impl<T:InferStr> InferStr for Bounds<T> {
     fn inf_str(&self, cx: &InferCtxt) -> ~str {
-        fmt!("{%s <: %s}",
+        format!("\\{{} <: {}\\}",
              self.lb.inf_str(cx),
              self.ub.inf_str(cx))
     }
@@ -69,8 +69,8 @@ impl<T:InferStr> InferStr for Bounds<T> {
 impl<V:Vid + ToStr,T:InferStr> InferStr for VarValue<V, T> {
     fn inf_str(&self, cx: &InferCtxt) -> ~str {
         match *self {
-          Redirect(ref vid) => fmt!("Redirect(%s)", vid.to_str()),
-          Root(ref pt, rk) => fmt!("Root(%s, %s)", pt.inf_str(cx),
+          Redirect(ref vid) => format!("Redirect({})", vid.to_str()),
+          Root(ref pt, rk) => format!("Root({}, {})", pt.inf_str(cx),
                                rk.to_str_radix(10u))
         }
     }
diff --git a/src/librustc/middle/typeck/infer/unify.rs b/src/librustc/middle/typeck/infer/unify.rs
index 5ebbee8986b..c05306a27be 100644
--- a/src/librustc/middle/typeck/infer/unify.rs
+++ b/src/librustc/middle/typeck/infer/unify.rs
@@ -85,8 +85,8 @@ impl UnifyInferCtxtMethods for InferCtxt {
             let var_val = match vb.vals.find(&vid_u) {
                 Some(&ref var_val) => (*var_val).clone(),
                 None => {
-                    tcx.sess.bug(fmt!(
-                        "failed lookup of vid `%u`", vid_u));
+                    tcx.sess.bug(format!(
+                        "failed lookup of vid `{}`", vid_u));
                 }
             };
             match var_val {
@@ -116,7 +116,7 @@ impl UnifyInferCtxtMethods for InferCtxt {
          * Sets the value for `vid` to `new_v`.  `vid` MUST be a root node!
          */
 
-        debug!("Updating variable %s to %s",
+        debug2!("Updating variable {} to {}",
                vid.to_str(), new_v.inf_str(self));
 
         let vb = UnifyVid::appropriate_vals_and_bindings(self);
@@ -134,8 +134,8 @@ impl UnifyInferCtxtMethods for InferCtxt {
         // Rank optimization: if you don't know what it is, check
         // out <http://en.wikipedia.org/wiki/Disjoint-set_data_structure>
 
-        debug!("unify(node_a(id=%?, rank=%?), \
-                node_b(id=%?, rank=%?))",
+        debug2!("unify(node_a(id={:?}, rank={:?}), \
+                node_b(id={:?}, rank={:?}))",
                node_a.root, node_a.rank,
                node_b.root, node_b.rank);
 
diff --git a/src/librustc/middle/typeck/mod.rs b/src/librustc/middle/typeck/mod.rs
index fbd3088902f..5db706765e9 100644
--- a/src/librustc/middle/typeck/mod.rs
+++ b/src/librustc/middle/typeck/mod.rs
@@ -178,7 +178,7 @@ impl Repr for vtable_origin {
     fn repr(&self, tcx: ty::ctxt) -> ~str {
         match *self {
             vtable_static(def_id, ref tys, ref vtable_res) => {
-                fmt!("vtable_static(%?:%s, %s, %s)",
+                format!("vtable_static({:?}:{}, {}, {})",
                      def_id,
                      ty::item_path_str(tcx, def_id),
                      tys.repr(tcx),
@@ -186,7 +186,7 @@ impl Repr for vtable_origin {
             }
 
             vtable_param(x, y) => {
-                fmt!("vtable_param(%?, %?)", x, y)
+                format!("vtable_param({:?}, {:?})", x, y)
             }
         }
     }
@@ -208,7 +208,7 @@ pub struct impl_res {
 
 impl Repr for impl_res {
     fn repr(&self, tcx: ty::ctxt) -> ~str {
-        fmt!("impl_res {trait_vtables=%s, self_vtables=%s}",
+        format!("impl_res \\{trait_vtables={}, self_vtables={}\\}",
              self.trait_vtables.repr(tcx),
              self.self_vtables.repr(tcx))
     }
@@ -226,7 +226,7 @@ pub struct CrateCtxt {
 
 // Functions that write types into the node type table
 pub fn write_ty_to_tcx(tcx: ty::ctxt, node_id: ast::NodeId, ty: ty::t) {
-    debug!("write_ty_to_tcx(%d, %s)", node_id, ppaux::ty_to_str(tcx, ty));
+    debug2!("write_ty_to_tcx({}, {})", node_id, ppaux::ty_to_str(tcx, ty));
     assert!(!ty::type_needs_infer(ty));
     tcx.node_types.insert(node_id as uint, ty);
 }
@@ -234,7 +234,7 @@ pub fn write_substs_to_tcx(tcx: ty::ctxt,
                            node_id: ast::NodeId,
                            substs: ~[ty::t]) {
     if substs.len() > 0u {
-        debug!("write_substs_to_tcx(%d, %?)", node_id,
+        debug2!("write_substs_to_tcx({}, {:?})", node_id,
                substs.map(|t| ppaux::ty_to_str(tcx, *t)));
         assert!(substs.iter().all(|t| !ty::type_needs_infer(*t)));
         tcx.node_type_substs.insert(node_id, substs);
@@ -361,12 +361,12 @@ fn check_main_fn_ty(ccx: &CrateCtxt,
             });
 
             require_same_types(tcx, None, false, main_span, main_t, se_ty,
-                || fmt!("main function expects type: `%s`",
+                || format!("main function expects type: `{}`",
                         ppaux::ty_to_str(ccx.tcx, se_ty)));
         }
         _ => {
             tcx.sess.span_bug(main_span,
-                              fmt!("main has a non-function type: found `%s`",
+                              format!("main has a non-function type: found `{}`",
                                    ppaux::ty_to_str(tcx, main_t)));
         }
     }
@@ -409,12 +409,12 @@ fn check_start_fn_ty(ccx: &CrateCtxt,
             });
 
             require_same_types(tcx, None, false, start_span, start_t, se_ty,
-                || fmt!("start function expects type: `%s`", ppaux::ty_to_str(ccx.tcx, se_ty)));
+                || format!("start function expects type: `{}`", ppaux::ty_to_str(ccx.tcx, se_ty)));
 
         }
         _ => {
             tcx.sess.span_bug(start_span,
-                              fmt!("start has a non-function type: found `%s`",
+                              format!("start has a non-function type: found `{}`",
                                    ppaux::ty_to_str(tcx, start_t)));
         }
     }
diff --git a/src/librustc/middle/typeck/rscope.rs b/src/librustc/middle/typeck/rscope.rs
index 1967122745d..f6483a48ed0 100644
--- a/src/librustc/middle/typeck/rscope.rs
+++ b/src/librustc/middle/typeck/rscope.rs
@@ -235,7 +235,7 @@ impl RegionScope for TypeRscope {
             None => {
                 // if the self region is used, region parameterization should
                 // have inferred that this type is RP
-                fail!("region parameterization should have inferred that \
+                fail2!("region parameterization should have inferred that \
                         this type is RP");
             }
             Some(ref region_parameterization) => {
diff --git a/src/librustc/rustc.rs b/src/librustc/rustc.rs
index 320feae2ce7..a7065624395 100644
--- a/src/librustc/rustc.rs
+++ b/src/librustc/rustc.rs
@@ -135,7 +135,7 @@ pub fn version(argv0: &str) {
 }
 
 pub fn usage(argv0: &str) {
-    let message = fmt!("Usage: %s [OPTIONS] INPUT", argv0);
+    let message = format!("Usage: {} [OPTIONS] INPUT", argv0);
     println!("{}\n\
 Additional help:
     -W help             Print 'lint' options and default settings
@@ -388,7 +388,7 @@ pub fn monitor(f: ~fn(@diagnostic::Emitter)) {
                 }
             }
             // Fail so the process returns a failure code
-            fail!();
+            fail2!();
         }
     }
 }
diff --git a/src/librustc/util/common.rs b/src/librustc/util/common.rs
index 3ffbbdd8358..5058be7c166 100644
--- a/src/librustc/util/common.rs
+++ b/src/librustc/util/common.rs
@@ -29,9 +29,9 @@ pub fn time<T, U>(do_it: bool, what: ~str, u: U, f: &fn(U) -> T) -> T {
 pub fn indent<R>(op: &fn() -> R) -> R {
     // Use in conjunction with the log post-processor like `src/etc/indenter`
     // to make debug output more readable.
-    debug!(">>");
+    debug2!(">>");
     let r = op();
-    debug!("<< (Result = %?)", r);
+    debug2!("<< (Result = {:?})", r);
     r
 }
 
@@ -40,7 +40,7 @@ pub struct _indenter {
 }
 
 impl Drop for _indenter {
-    fn drop(&mut self) { debug!("<<"); }
+    fn drop(&mut self) { debug2!("<<"); }
 }
 
 pub fn _indenter(_i: ()) -> _indenter {
@@ -50,7 +50,7 @@ pub fn _indenter(_i: ()) -> _indenter {
 }
 
 pub fn indenter() -> _indenter {
-    debug!(">>");
+    debug2!(">>");
     _indenter(())
 }
 
@@ -120,7 +120,7 @@ pub fn local_rhs_span(l: @ast::Local, def: Span) -> Span {
 
 pub fn pluralize(n: uint, s: ~str) -> ~str {
     if n == 1 { s }
-    else { fmt!("%ss", s) }
+    else { format!("{}s", s) }
 }
 
 // A set of node IDs (used to keep track of which node IDs are for statements)
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index 9350bf8d3d9..bbca28f134f 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -51,11 +51,11 @@ pub fn note_and_explain_region(cx: ctxt,
       (ref str, Some(span)) => {
         cx.sess.span_note(
             span,
-            fmt!("%s%s%s", prefix, (*str), suffix));
+            format!("{}{}{}", prefix, (*str), suffix));
       }
       (ref str, None) => {
         cx.sess.note(
-            fmt!("%s%s%s", prefix, (*str), suffix));
+            format!("{}{}{}", prefix, (*str), suffix));
       }
     }
 }
@@ -98,7 +98,7 @@ pub fn explain_region_and_span(cx: ctxt, region: ty::Region)
           }
           Some(_) | None => {
             // this really should not happen
-            (fmt!("unknown scope: %d.  Please report a bug.", node_id),
+            (format!("unknown scope: {}.  Please report a bug.", node_id),
              None)
           }
         }
@@ -106,21 +106,21 @@ pub fn explain_region_and_span(cx: ctxt, region: ty::Region)
 
       re_free(ref fr) => {
         let prefix = match fr.bound_region {
-          br_anon(idx) => fmt!("the anonymous lifetime #%u defined on",
+          br_anon(idx) => format!("the anonymous lifetime \\#{} defined on",
                                idx + 1),
-          br_fresh(_) => fmt!("an anonymous lifetime defined on"),
-          _ => fmt!("the lifetime %s as defined on",
+          br_fresh(_) => format!("an anonymous lifetime defined on"),
+          _ => format!("the lifetime {} as defined on",
                     bound_region_ptr_to_str(cx, fr.bound_region))
         };
 
         match cx.items.find(&fr.scope_id) {
           Some(&ast_map::node_block(ref blk)) => {
             let (msg, opt_span) = explain_span(cx, "block", blk.span);
-            (fmt!("%s %s", prefix, msg), opt_span)
+            (format!("{} {}", prefix, msg), opt_span)
           }
           Some(_) | None => {
             // this really should not happen
-            (fmt!("%s node %d", prefix, fr.scope_id), None)
+            (format!("{} node {}", prefix, fr.scope_id), None)
           }
         }
       }
@@ -132,7 +132,7 @@ pub fn explain_region_and_span(cx: ctxt, region: ty::Region)
       // I believe these cases should not occur (except when debugging,
       // perhaps)
       re_infer(_) | re_bound(_) => {
-        (fmt!("lifetime %?", region), None)
+        (format!("lifetime {:?}", region), None)
       }
     };
 
@@ -140,7 +140,7 @@ pub fn explain_region_and_span(cx: ctxt, region: ty::Region)
         -> (~str, Option<Span>)
     {
         let lo = cx.sess.codemap.lookup_char_pos_adj(span.lo);
-        (fmt!("the %s at %u:%u", heading,
+        (format!("the {} at {}:{}", heading,
               lo.line, lo.col.to_uint()), Some(span))
     }
 }
@@ -154,11 +154,11 @@ pub fn bound_region_to_str(cx: ctxt,
                            br: bound_region) -> ~str {
     let space_str = if space { " " } else { "" };
 
-    if cx.sess.verbose() { return fmt!("%s%?%s", prefix, br, space_str); }
+    if cx.sess.verbose() { return format!("{}{:?}{}", prefix, br, space_str); }
 
     match br {
-      br_named(id)         => fmt!("%s'%s%s", prefix, cx.sess.str_of(id), space_str),
-      br_self              => fmt!("%s'self%s", prefix, space_str),
+      br_named(id)         => format!("{}'{}{}", prefix, cx.sess.str_of(id), space_str),
+      br_self              => format!("{}'self{}", prefix, space_str),
       br_anon(_)           => prefix.to_str(),
       br_fresh(_)          => prefix.to_str(),
       br_cap_avoid(_, br)  => bound_region_to_str(cx, prefix, space, *br)
@@ -168,37 +168,37 @@ pub fn bound_region_to_str(cx: ctxt,
 pub fn re_scope_id_to_str(cx: ctxt, node_id: ast::NodeId) -> ~str {
     match cx.items.find(&node_id) {
       Some(&ast_map::node_block(ref blk)) => {
-        fmt!("<block at %s>",
+        format!("<block at {}>",
              cx.sess.codemap.span_to_str(blk.span))
       }
       Some(&ast_map::node_expr(expr)) => {
         match expr.node {
           ast::ExprCall(*) => {
-            fmt!("<call at %s>",
+            format!("<call at {}>",
                  cx.sess.codemap.span_to_str(expr.span))
           }
           ast::ExprMatch(*) => {
-            fmt!("<match at %s>",
+            format!("<match at {}>",
                  cx.sess.codemap.span_to_str(expr.span))
           }
           ast::ExprAssignOp(*) |
           ast::ExprUnary(*) |
           ast::ExprBinary(*) |
           ast::ExprIndex(*) => {
-            fmt!("<method at %s>",
+            format!("<method at {}>",
                  cx.sess.codemap.span_to_str(expr.span))
           }
           _ => {
-            fmt!("<expression at %s>",
+            format!("<expression at {}>",
                  cx.sess.codemap.span_to_str(expr.span))
           }
         }
       }
       None => {
-        fmt!("<unknown-%d>", node_id)
+        format!("<unknown-{}>", node_id)
       }
       _ => { cx.sess.bug(
-          fmt!("re_scope refers to %s",
+          format!("re_scope refers to {}",
                ast_map::node_id_to_str(cx.items, node_id,
                                        token::get_ident_interner()))) }
     }
@@ -215,7 +215,7 @@ pub fn region_to_str(cx: ctxt, prefix: &str, space: bool, region: Region) -> ~st
     let space_str = if space { " " } else { "" };
 
     if cx.sess.verbose() {
-        return fmt!("%s%?%s", prefix, region, space_str);
+        return format!("{}{:?}{}", prefix, region, space_str);
     }
 
     // These printouts are concise.  They do not contain all the information
@@ -230,8 +230,8 @@ pub fn region_to_str(cx: ctxt, prefix: &str, space: bool, region: Region) -> ~st
             bound_region_to_str(cx, prefix, space, br)
         }
         re_infer(ReVar(_)) => prefix.to_str(),
-        re_static => fmt!("%s'static%s", prefix, space_str),
-        re_empty => fmt!("%s'<empty>%s", prefix, space_str)
+        re_static => format!("{}'static{}", prefix, space_str),
+        re_empty => format!("{}'<empty>{}", prefix, space_str)
     }
 }
 
@@ -248,12 +248,12 @@ pub fn mt_to_str(cx: ctxt, m: &mt) -> ~str {
 
 pub fn mt_to_str_wrapped(cx: ctxt, before: &str, m: &mt, after: &str) -> ~str {
     let mstr = mutability_to_str(m.mutbl);
-    return fmt!("%s%s%s%s", mstr, before, ty_to_str(cx, m.ty), after);
+    return format!("{}{}{}{}", mstr, before, ty_to_str(cx, m.ty), after);
 }
 
 pub fn vstore_to_str(cx: ctxt, vs: ty::vstore) -> ~str {
     match vs {
-      ty::vstore_fixed(n) => fmt!("%u", n),
+      ty::vstore_fixed(n) => format!("{}", n),
       ty::vstore_uniq => ~"~",
       ty::vstore_box => ~"@",
       ty::vstore_slice(r) => region_ptr_to_str(cx, r)
@@ -271,17 +271,17 @@ pub fn trait_store_to_str(cx: ctxt, s: ty::TraitStore) -> ~str {
 pub fn vstore_ty_to_str(cx: ctxt, mt: &mt, vs: ty::vstore) -> ~str {
     match vs {
         ty::vstore_fixed(_) => {
-            fmt!("[%s, .. %s]", mt_to_str(cx, mt), vstore_to_str(cx, vs))
+            format!("[{}, .. {}]", mt_to_str(cx, mt), vstore_to_str(cx, vs))
         }
         _ => {
-            fmt!("%s%s", vstore_to_str(cx, vs), mt_to_str_wrapped(cx, "[", mt, "]"))
+            format!("{}{}", vstore_to_str(cx, vs), mt_to_str_wrapped(cx, "[", mt, "]"))
         }
     }
 }
 
 pub fn vec_map_to_str<T>(ts: &[T], f: &fn(t: &T) -> ~str) -> ~str {
     let tstrs = ts.map(f);
-    fmt!("[%s]", tstrs.connect(", "))
+    format!("[{}]", tstrs.connect(", "))
 }
 
 pub fn tys_to_str(cx: ctxt, ts: &[t]) -> ~str {
@@ -289,7 +289,7 @@ pub fn tys_to_str(cx: ctxt, ts: &[t]) -> ~str {
 }
 
 pub fn fn_sig_to_str(cx: ctxt, typ: &ty::FnSig) -> ~str {
-    fmt!("fn%s -> %s",
+    format!("fn{} -> {}",
          tys_to_str(cx, typ.inputs.map(|a| *a)),
          ty_to_str(cx, typ.output))
 }
@@ -397,7 +397,7 @@ pub fn ty_to_str(cx: ctxt, typ: t) -> ~str {
                        &m.fty.sig) + ";"
     }
     fn field_to_str(cx: ctxt, f: field) -> ~str {
-        return fmt!("%s: %s", cx.sess.str_of(f.ident), mt_to_str(cx, &f.mt));
+        return format!("{}: {}", cx.sess.str_of(f.ident), mt_to_str(cx, &f.mt));
     }
 
     // if there is an id, print that instead of the structural type:
@@ -425,7 +425,7 @@ pub fn ty_to_str(cx: ctxt, typ: t) -> ~str {
       ty_rptr(r, ref tm) => {
         region_ptr_to_str(cx, r) + mt_to_str(cx, tm)
       }
-      ty_unboxed_vec(ref tm) => { fmt!("unboxed_vec<%s>", mt_to_str(cx, tm)) }
+      ty_unboxed_vec(ref tm) => { format!("unboxed_vec<{}>", mt_to_str(cx, tm)) }
       ty_type => ~"type",
       ty_tup(ref elems) => {
         let strs = elems.map(|elem| ty_to_str(cx, *elem));
@@ -447,10 +447,10 @@ pub fn ty_to_str(cx: ctxt, typ: t) -> ~str {
               }
               None => {
                   // This should not happen...
-                  fmt!("BUG[%?]", id)
+                  format!("BUG[{:?}]", id)
               }
           };
-          if !cx.sess.verbose() { ident } else { fmt!("%s:%?", ident, did) }
+          if !cx.sess.verbose() { ident } else { format!("{}:{:?}", ident, did) }
       }
       ty_self(*) => ~"Self",
       ty_enum(did, ref substs) | ty_struct(did, ref substs) => {
@@ -464,13 +464,13 @@ pub fn ty_to_str(cx: ctxt, typ: t) -> ~str {
         let ty = parameterized(cx, base, &substs.regions, substs.tps);
         let bound_sep = if bounds.is_empty() { "" } else { ":" };
         let bound_str = bounds.repr(cx);
-        fmt!("%s%s%s%s%s", trait_store_to_str(cx, s), mutability_to_str(mutbl), ty,
+        format!("{}{}{}{}{}", trait_store_to_str(cx, s), mutability_to_str(mutbl), ty,
                            bound_sep, bound_str)
       }
       ty_evec(ref mt, vs) => {
         vstore_ty_to_str(cx, mt, vs)
       }
-      ty_estr(vs) => fmt!("%s%s", vstore_to_str(cx, vs), "str"),
+      ty_estr(vs) => format!("{}{}", vstore_to_str(cx, vs), "str"),
       ty_opaque_box => ~"@?",
       ty_opaque_closure_ptr(ast::BorrowedSigil) => ~"&closure",
       ty_opaque_closure_ptr(ast::ManagedSigil) => ~"@closure",
@@ -498,9 +498,9 @@ pub fn parameterized(cx: ctxt,
     }
 
     if strs.len() > 0u {
-        fmt!("%s<%s>", base, strs.connect(","))
+        format!("{}<{}>", base, strs.connect(","))
     } else {
-        fmt!("%s", base)
+        format!("{}", base)
     }
 }
 
@@ -514,7 +514,7 @@ impl<T:Repr> Repr for Option<T> {
     fn repr(&self, tcx: ctxt) -> ~str {
         match self {
             &None => ~"None",
-            &Some(ref t) => fmt!("Some(%s)", t.repr(tcx))
+            &Some(ref t) => format!("Some({})", t.repr(tcx))
         }
     }
 }
@@ -560,7 +560,7 @@ impl<T:Repr> Repr for ~[T] {
 
 impl Repr for ty::TypeParameterDef {
     fn repr(&self, tcx: ctxt) -> ~str {
-        fmt!("TypeParameterDef {%?, bounds: %s}",
+        format!("TypeParameterDef \\{{:?}, bounds: {}\\}",
              self.def_id, self.bounds.repr(tcx))
     }
 }
@@ -573,7 +573,7 @@ impl Repr for ty::t {
 
 impl Repr for ty::substs {
     fn repr(&self, tcx: ctxt) -> ~str {
-        fmt!("substs(regions=%s, self_ty=%s, tps=%s)",
+        format!("substs(regions={}, self_ty={}, tps={})",
              self.regions.repr(tcx),
              self.self_ty.repr(tcx),
              self.tps.repr(tcx))
@@ -615,7 +615,7 @@ impl Repr for ty::TraitRef {
 
 impl Repr for ast::Expr {
     fn repr(&self, tcx: ctxt) -> ~str {
-        fmt!("expr(%d: %s)",
+        format!("expr({}: {})",
              self.id,
              pprust::expr_to_str(self, tcx.sess.intr()))
     }
@@ -623,7 +623,7 @@ impl Repr for ast::Expr {
 
 impl Repr for ast::Pat {
     fn repr(&self, tcx: ctxt) -> ~str {
-        fmt!("pat(%d: %s)",
+        format!("pat({}: {})",
              self.id,
              pprust::pat_to_str(self, tcx.sess.intr()))
     }
@@ -654,18 +654,18 @@ impl Repr for ast::DefId {
                 Some(&ast_map::node_trait_method(*)) |
                 Some(&ast_map::node_variant(*)) |
                 Some(&ast_map::node_struct_ctor(*)) => {
-                    return fmt!("%?:%s", *self, ty::item_path_str(tcx, *self));
+                    return format!("{:?}:{}", *self, ty::item_path_str(tcx, *self));
                 }
                 _ => {}
             }
         }
-        return fmt!("%?", *self);
+        return format!("{:?}", *self);
     }
 }
 
 impl Repr for ty::ty_param_bounds_and_ty {
     fn repr(&self, tcx: ctxt) -> ~str {
-        fmt!("ty_param_bounds_and_ty {generics: %s, ty: %s}",
+        format!("ty_param_bounds_and_ty \\{generics: {}, ty: {}\\}",
              self.generics.repr(tcx),
              self.ty.repr(tcx))
     }
@@ -673,7 +673,7 @@ impl Repr for ty::ty_param_bounds_and_ty {
 
 impl Repr for ty::Generics {
     fn repr(&self, tcx: ctxt) -> ~str {
-        fmt!("Generics {type_param_defs: %s, region_param: %?}",
+        format!("Generics \\{type_param_defs: {}, region_param: {:?}\\}",
              self.type_param_defs.repr(tcx),
              self.region_param)
     }
@@ -681,8 +681,8 @@ impl Repr for ty::Generics {
 
 impl Repr for ty::Method {
     fn repr(&self, tcx: ctxt) -> ~str {
-        fmt!("method {ident: %s, generics: %s, transformed_self_ty: %s, \
-              fty: %s, explicit_self: %s, vis: %s, def_id: %s}",
+        format!("method \\{ident: {}, generics: {}, transformed_self_ty: {}, \
+              fty: {}, explicit_self: {}, vis: {}, def_id: {}\\}",
              self.ident.repr(tcx),
              self.generics.repr(tcx),
              self.transformed_self_ty.repr(tcx),
@@ -701,19 +701,19 @@ impl Repr for ast::Ident {
 
 impl Repr for ast::explicit_self_ {
     fn repr(&self, _tcx: ctxt) -> ~str {
-        fmt!("%?", *self)
+        format!("{:?}", *self)
     }
 }
 
 impl Repr for ast::visibility {
     fn repr(&self, _tcx: ctxt) -> ~str {
-        fmt!("%?", *self)
+        format!("{:?}", *self)
     }
 }
 
 impl Repr for ty::BareFnTy {
     fn repr(&self, tcx: ctxt) -> ~str {
-        fmt!("BareFnTy {purity: %?, abis: %s, sig: %s}",
+        format!("BareFnTy \\{purity: {:?}, abis: {}, sig: {}\\}",
              self.purity,
              self.abis.to_str(),
              self.sig.repr(tcx))
@@ -728,9 +728,9 @@ impl Repr for ty::FnSig {
 
 impl Repr for typeck::method_map_entry {
     fn repr(&self, tcx: ctxt) -> ~str {
-        fmt!("method_map_entry {self_arg: %s, \
-              explicit_self: %s, \
-              origin: %s}",
+        format!("method_map_entry \\{self_arg: {}, \
+              explicit_self: {}, \
+              origin: {}\\}",
              self.self_ty.repr(tcx),
              self.explicit_self.repr(tcx),
              self.origin.repr(tcx))
@@ -741,7 +741,7 @@ impl Repr for typeck::method_origin {
     fn repr(&self, tcx: ctxt) -> ~str {
         match self {
             &typeck::method_static(def_id) => {
-                fmt!("method_static(%s)", def_id.repr(tcx))
+                format!("method_static({})", def_id.repr(tcx))
             }
             &typeck::method_param(ref p) => {
                 p.repr(tcx)
@@ -755,7 +755,7 @@ impl Repr for typeck::method_origin {
 
 impl Repr for typeck::method_param {
     fn repr(&self, tcx: ctxt) -> ~str {
-        fmt!("method_param(%s,%?,%?,%?)",
+        format!("method_param({},{:?},{:?},{:?})",
              self.trait_id.repr(tcx),
              self.method_num,
              self.param_num,
@@ -765,7 +765,7 @@ impl Repr for typeck::method_param {
 
 impl Repr for typeck::method_object {
     fn repr(&self, tcx: ctxt) -> ~str {
-        fmt!("method_object(%s,%?,%?)",
+        format!("method_object({},{:?},{:?})",
              self.trait_id.repr(tcx),
              self.method_num,
              self.real_index)
@@ -775,7 +775,7 @@ impl Repr for typeck::method_object {
 
 impl Repr for ty::RegionVid {
     fn repr(&self, _tcx: ctxt) -> ~str {
-        fmt!("%?", *self)
+        format!("{:?}", *self)
     }
 }
 
@@ -784,7 +784,7 @@ impl Repr for ty::TraitStore {
         match self {
             &ty::BoxTraitStore => ~"@Trait",
             &ty::UniqTraitStore => ~"~Trait",
-            &ty::RegionTraitStore(r) => fmt!("&%s Trait", r.repr(tcx))
+            &ty::RegionTraitStore(r) => format!("&{} Trait", r.repr(tcx))
         }
     }
 }
@@ -807,7 +807,7 @@ impl Repr for ast_map::path_elt {
 
 impl Repr for ty::BuiltinBound {
     fn repr(&self, _tcx: ctxt) -> ~str {
-        fmt!("%?", *self)
+        format!("{:?}", *self)
     }
 }