diff --git a/src/bootstrap/bin/rustc.rs b/src/bootstrap/bin/rustc.rs
index e81595a8c62..f2b2f6f1eeb 100644
--- a/src/bootstrap/bin/rustc.rs
+++ b/src/bootstrap/bin/rustc.rs
@@ -326,7 +326,7 @@ fn main() {
             let start = Instant::now();
             let status = cmd
                 .status()
-                .expect(&format!("\n\n failed to run {:?}", cmd));
+                .unwrap_or_else(|_| panic!("\n\n failed to run {:?}", cmd));
             let dur = start.elapsed();
 
             let is_test = args.iter().any(|a| a == "--test");
@@ -346,7 +346,7 @@ fn main() {
         }
     }
 
-    let code = exec_cmd(&mut cmd).expect(&format!("\n\n failed to run {:?}", cmd));
+    let code = exec_cmd(&mut cmd).unwrap_or_else(|_| panic!("\n\n failed to run {:?}", cmd));
     std::process::exit(code);
 }
 
diff --git a/src/bootstrap/install.rs b/src/bootstrap/install.rs
index 97fd6f77646..cb28698aa3d 100644
--- a/src/bootstrap/install.rs
+++ b/src/bootstrap/install.rs
@@ -75,7 +75,7 @@ fn install_sh(
     let libdir_default = PathBuf::from("lib");
     let mandir_default = datadir_default.join("man");
     let prefix = builder.config.prefix.as_ref().map_or(prefix_default, |p| {
-        fs::canonicalize(p).expect(&format!("could not canonicalize {}", p.display()))
+        fs::canonicalize(p).unwrap_or_else(|_| panic!("could not canonicalize {}", p.display()))
     });
     let sysconfdir = builder.config.sysconfdir.as_ref().unwrap_or(&sysconfdir_default);
     let datadir = builder.config.datadir.as_ref().unwrap_or(&datadir_default);
diff --git a/src/librustc_codegen_llvm/back/rpath.rs b/src/librustc_codegen_llvm/back/rpath.rs
index f46205cb590..e73073cfad0 100644
--- a/src/librustc_codegen_llvm/back/rpath.rs
+++ b/src/librustc_codegen_llvm/back/rpath.rs
@@ -114,8 +114,8 @@ fn get_rpath_relative_to_output(config: &mut RPathConfig, lib: &Path) -> String
     let mut output = cwd.join(&config.out_filename);
     output.pop();
     let output = fs::canonicalize(&output).unwrap_or(output);
-    let relative = path_relative_from(&lib, &output)
-        .expect(&format!("couldn't create relative path from {:?} to {:?}", output, lib));
+    let relative = path_relative_from(&lib, &output).unwrap_or_else(||
+        panic!("couldn't create relative path from {:?} to {:?}", output, lib));
     // FIXME (#9639): This needs to handle non-utf8 paths
     format!("{}/{}", prefix,
             relative.to_str().expect("non-utf8 component in path"))
diff --git a/src/librustc_codegen_llvm/base.rs b/src/librustc_codegen_llvm/base.rs
index 6d37f1ca3ca..223c04f420f 100644
--- a/src/librustc_codegen_llvm/base.rs
+++ b/src/librustc_codegen_llvm/base.rs
@@ -1277,7 +1277,7 @@ pub fn provide(providers: &mut Providers) {
         all.iter()
             .find(|cgu| *cgu.name() == name)
             .cloned()
-            .expect(&format!("failed to find cgu with name {:?}", name))
+            .unwrap_or_else(|| panic!("failed to find cgu with name {:?}", name))
     };
     providers.compile_codegen_unit = compile_codegen_unit;
 
diff --git a/src/libsyntax_ext/format_foreign.rs b/src/libsyntax_ext/format_foreign.rs
index ff9663cdd3c..8ccb3be1ad9 100644
--- a/src/libsyntax_ext/format_foreign.rs
+++ b/src/libsyntax_ext/format_foreign.rs
@@ -232,11 +232,11 @@ pub mod printf {
     impl Num {
         fn from_str(s: &str, arg: Option<&str>) -> Self {
             if let Some(arg) = arg {
-                Num::Arg(arg.parse().expect(&format!("invalid format arg `{:?}`", arg)))
+                Num::Arg(arg.parse().unwrap_or_else(|_| panic!("invalid format arg `{:?}`", arg)))
             } else if s == "*" {
                 Num::Next
             } else {
-                Num::Num(s.parse().expect(&format!("invalid format num `{:?}`", s)))
+                Num::Num(s.parse().unwrap_or_else(|_| panic!("invalid format num `{:?}`", s)))
             }
         }