address review comments

src/librustc_codegen_llvm/back/link.rs

@@ -69,18 +69,13 @@ pub fn get_linker(sess: &Session, linker: &Path, flavor: LinkerFlavor) -> (PathB
     // This worked historically but is needed manually since #42436 (regression
     // was tagged as #42791) and some more info can be found on #44443 for
     // emscripten itself.
-    let mut cmd = (|| {
-        if let Some(linker) = linker.to_str() {
-            if cfg!(windows) && linker.ends_with(".bat") {
-                return Command::bat_script(linker)
-            }
-        }
-        match flavor {
+    let mut cmd = match linker.to_str() {
+        Some(linker) if cfg!(windows) && linker.ends_with(".bat") => Command::bat_script(linker),
+        _ => match flavor {
             LinkerFlavor::Lld(f) => Command::lld(linker, f),
             _ => Command::new(linker),
-
         }
-    })();
+    };
 
     let msvc_tool = windows_registry::find_tool(&sess.opts.target_triple.triple(), "link.exe");
 
@@ -600,33 +595,26 @@ fn print_native_static_libs(sess: &Session, all_native_libs: &[NativeLibrary]) {
     }
 }
 
-pub fn linker_and_flavor(sess: &Session) -> Result<(PathBuf, LinkerFlavor), ()> {
-    fn from<F>(
+pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
+    fn infer_from(
         sess: &Session,
         linker: Option<PathBuf>,
         flavor: Option<LinkerFlavor>,
-        otherwise: F,
-    ) -> Result<(PathBuf, LinkerFlavor), ()>
-    where
-        F: FnOnce() -> Result<(PathBuf, LinkerFlavor), ()>
-    {
+    ) -> Option<(PathBuf, LinkerFlavor)> {
         match (linker, flavor) {
-            (Some(linker), Some(flavor)) => Ok((linker, flavor)),
+            (Some(linker), Some(flavor)) => Some((linker, flavor)),
             // only the linker flavor is known; use the default linker for the selected flavor
-            (None, Some(flavor)) => Ok((PathBuf::from(match flavor {
-                LinkerFlavor::Em => "emcc",
+            (None, Some(flavor)) => Some((PathBuf::from(match flavor {
+                LinkerFlavor::Em  => if cfg!(windows) { "emcc.bat" } else { "emcc" },
                 LinkerFlavor::Gcc => "gcc",
                 LinkerFlavor::Ld => "ld",
                 LinkerFlavor::Msvc => "link.exe",
                 LinkerFlavor::Lld(_) => "lld",
             }), flavor)),
-            // infer the linker flavor from the linker name
             (Some(linker), None) => {
-                let stem = linker.file_stem().and_then(|stem| stem.to_str()).ok_or_else(|| {
-                    sess
-                        .struct_err(&format!("couldn't extract file stem from specified linker"))
-                        .emit();
-                })?.to_owned();
+                let stem = linker.file_stem().and_then(|stem| stem.to_str()).unwrap_or_else(|| {
+                    sess.fatal("couldn't extract file stem from specified linker");
+                }).to_owned();
 
                 let flavor = if stem == "emcc" {
                     LinkerFlavor::Em
@@ -637,32 +625,35 @@ pub fn linker_and_flavor(sess: &Session) -> Result<(PathBuf, LinkerFlavor), ()>
                 } else if stem == "link" || stem == "lld-link" {
                     LinkerFlavor::Msvc
                 } else {
-                    sess
-                        .struct_err(&format!("couldn't infer linker flavor from specified linker"))
-                        .emit();
-                    return Err(());
+                    // fall back to the value in the target spec
+                    sess.target.target.linker_flavor
                 };
 
-                Ok((linker, flavor))
+                Some((linker, flavor))
             },
-            (None, None) => otherwise(),
+            (None, None) => None,
         }
     }
 
     // linker and linker flavor specified via command line have precedence over what the target
     // specification specifies
-    from(sess, sess.opts.cg.linker.clone(), sess.opts.debugging_opts.linker_flavor, || {
-        from(
-            sess,
-            sess.target.target.options.linker.clone().map(PathBuf::from),
-            Some(sess.target.target.linker_flavor),
-            || {
-                sess
-                    .struct_err(&format!("no linker or linker flavor information provided"))
-                    .emit();
-                Err(())
-            })
-    })
+    if let Some(ret) = infer_from(
+        sess,
+        sess.opts.cg.linker.clone(),
+        sess.opts.debugging_opts.linker_flavor,
+    ) {
+        return ret;
+    }
+
+    if let Some(ret) = infer_from(
+        sess,
+        sess.target.target.options.linker.clone().map(PathBuf::from),
+        Some(sess.target.target.linker_flavor),
+    ) {
+        return ret;
+    }
+
+    sess.fatal("Not enough information provided to determine how to invoke the linker");
 }
 
 // Create a dynamic library or executable
@@ -675,12 +666,7 @@ fn link_natively(sess: &Session,
                  codegen_results: &CodegenResults,
                  tmpdir: &Path) {
     info!("preparing {:?} to {:?}", crate_type, out_filename);
-    let (linker, flavor) = if let Ok((linker, flavor)) = linker_and_flavor(sess) {
-        (linker, flavor)
-    } else {
-        sess.abort_if_errors();
-        return;
-    };
+    let (linker, flavor) = linker_and_flavor(sess);
 
     // The invocations of cc share some flags across platforms
     let (pname, mut cmd) = get_linker(sess, &linker, flavor);

src/librustc_codegen_llvm/back/write.rs

@@ -1503,17 +1503,14 @@ fn start_executing_work(tcx: TyCtxt,
 
     let assembler_cmd = if modules_config.no_integrated_as {
         // HACK: currently we use linker (gcc) as our assembler
-        if let Ok((linker, flavor)) = link::linker_and_flavor(sess) {
-            let (name, mut cmd) = get_linker(sess, &linker, flavor);
-            cmd.args(&sess.target.target.options.asm_args);
-            Some(Arc::new(AssemblerCommand {
-                name,
-                cmd,
-            }))
-        } else {
-            sess.abort_if_errors();
-            None
-        }
+        let (linker, flavor) = link::linker_and_flavor(sess);
+
+        let (name, mut cmd) = get_linker(sess, &linker, flavor);
+        cmd.args(&sess.target.target.options.asm_args);
+        Some(Arc::new(AssemblerCommand {
+            name,
+            cmd,
+        }))
     } else {
         None
     };