codegen_llvm_back: improve common patterns

src/librustc_codegen_llvm/back/archive.rs

@@ -185,13 +185,8 @@ impl<'a> ArchiveBuilder<'a> {
     /// Combine the provided files, rlibs, and native libraries into a single
     /// `Archive`.
     pub fn build(&mut self) {
-        let kind = match self.llvm_archive_kind() {
+        let kind = self.llvm_archive_kind().unwrap_or_else(|kind|
-            Ok(kind) => kind,
+            self.config.sess.fatal(&format!("Don't know how to build archive of type: {}", kind)));
-            Err(kind) => {
-                self.config.sess.fatal(&format!("Don't know how to build archive of type: {}",
-                                                kind));
-            }
-        };
 
         if let Err(e) = self.build_with_llvm(kind) {
             self.config.sess.fatal(&format!("failed to build archive: {}", e));

src/librustc_codegen_llvm/back/link.rs

@@ -107,13 +107,10 @@ pub fn get_linker(sess: &Session, linker: &Path, flavor: LinkerFlavor) -> (PathB
 }
 
 pub fn remove(sess: &Session, path: &Path) {
-    match fs::remove_file(path) {
+    if let Err(e) = fs::remove_file(path) {
-        Ok(..) => {}
+        sess.err(&format!("failed to remove {}: {}",
-        Err(e) => {
+                          path.display(),
-            sess.err(&format!("failed to remove {}: {}",
+                          e));
-                             path.display(),
-                             e));
-        }
     }
 }
 
@@ -184,7 +181,7 @@ fn preserve_objects_for_their_debuginfo(sess: &Session) -> bool {
     // the objects as they're losslessly contained inside the archives.
     let output_linked = sess.crate_types.borrow()
         .iter()
-        .any(|x| *x != config::CrateType::Rlib && *x != config::CrateType::Staticlib);
+        .any(|&x| x != config::CrateType::Rlib && x != config::CrateType::Staticlib);
     if !output_linked {
         return false
     }
@@ -289,13 +286,10 @@ fn link_binary_output(sess: &Session,
         // final destination, with a `fs::rename` call. In order for the rename to
         // always succeed, the temporary file needs to be on the same filesystem,
         // which is why we create it inside the output directory specifically.
-        let metadata_tmpdir = match TempFileBuilder::new()
+        let metadata_tmpdir = TempFileBuilder::new()
             .prefix("rmeta")
             .tempdir_in(out_filename.parent().unwrap())
-        {
+            .unwrap_or_else(|err| sess.fatal(&format!("couldn't create a temp dir: {}", err)));
-            Ok(tmpdir) => tmpdir,
-            Err(err) => sess.fatal(&format!("couldn't create a temp dir: {}", err)),
-        };
         let metadata = emit_metadata(sess, codegen_results, &metadata_tmpdir);
         if let Err(e) = fs::rename(metadata, &out_filename) {
             sess.fatal(&format!("failed to write {}: {}", out_filename.display(), e));
@@ -303,10 +297,8 @@ fn link_binary_output(sess: &Session,
         out_filenames.push(out_filename);
     }
 
-    let tmpdir = match TempFileBuilder::new().prefix("rustc").tempdir() {
+    let tmpdir = TempFileBuilder::new().prefix("rustc").tempdir().unwrap_or_else(|err|
-        Ok(tmpdir) => tmpdir,
+        sess.fatal(&format!("couldn't create a temp dir: {}", err)));
-        Err(err) => sess.fatal(&format!("couldn't create a temp dir: {}", err)),
-    };
 
     if outputs.outputs.should_codegen() {
         let out_filename = out_filename(sess, crate_type, outputs, crate_name);
@@ -869,9 +861,8 @@ fn link_natively(sess: &Session,
         sess.opts.debuginfo != DebugInfo::None &&
         !preserve_objects_for_their_debuginfo(sess)
     {
-        match Command::new("dsymutil").arg(out_filename).output() {
+        if let Err(e) = Command::new("dsymutil").arg(out_filename).output() {
-            Ok(..) => {}
+            sess.fatal(&format!("failed to run dsymutil: {}", e))
-            Err(e) => sess.fatal(&format!("failed to run dsymutil: {}", e)),
         }
     }
 

src/librustc_codegen_llvm/back/lto.rs

@@ -919,12 +919,6 @@ impl ThinLTOImports {
 }
 
 fn module_name_to_str(c_str: &CStr) -> &str {
-    match c_str.to_str() {
+    c_str.to_str().unwrap_or_else(|e|
-        Ok(s) => s,
+        bug!("Encountered non-utf8 LLVM module name `{}`: {}", c_str.to_string_lossy(), e))
-        Err(e) => {
-            bug!("Encountered non-utf8 LLVM module name `{}`: {}",
-                c_str.to_string_lossy(),
-                e)
-        }
-    }
 }

src/librustc_codegen_llvm/back/wasm.rs

@@ -42,7 +42,7 @@ const WASM_EXTERNAL_KIND_GLOBAL: u8 = 3;
 /// https://github.com/llvm-mirror/llvm/commit/0f32e1365, although support still
 /// needs to be added, tracked at https://bugs.llvm.org/show_bug.cgi?id=37168
 pub fn rewrite_imports(path: &Path, import_map: &FxHashMap<String, String>) {
-    if import_map.len() == 0 {
+    if import_map.is_empty() {
         return
     }
 
@@ -127,7 +127,7 @@ impl<'a> Iterator for WasmSections<'a> {
     type Item = (u8, &'a [u8]);
 
     fn next(&mut self) -> Option<(u8, &'a [u8])> {
-        if self.0.data.len() == 0 {
+        if self.0.data.is_empty() {
             return None
         }
 

src/librustc_codegen_llvm/back/write.rs

@@ -1440,15 +1440,12 @@ fn execute_copy_from_cache_work_item(cgcx: &CodegenContext,
                module.name,
                source_file,
                obj_out.display());
-        match link_or_copy(&source_file, &obj_out) {
+        if let Err(err) = link_or_copy(&source_file, &obj_out) {
-            Ok(_) => { }
+            let diag_handler = cgcx.create_diag_handler();
-            Err(err) => {
+            diag_handler.err(&format!("unable to copy {} to {}: {}",
-                let diag_handler = cgcx.create_diag_handler();
+                                      source_file.display(),
-                diag_handler.err(&format!("unable to copy {} to {}: {}",
+                                      obj_out.display(),
-                                          source_file.display(),
+                                      err));
-                                          obj_out.display(),
-                                          err));
-            }
         }
     }
 

src/librustc_codegen_utils/linker.rs

@@ -343,17 +343,13 @@ impl<'a> Linker for GccLinker<'a> {
     }
 
     fn debuginfo(&mut self) {
-        match self.sess.opts.debuginfo {
+        if let DebugInfo::None = self.sess.opts.debuginfo {
-            DebugInfo::None => {
+            // If we are building without debuginfo enabled and we were called with
-                // If we are building without debuginfo enabled and we were called with
+            // `-Zstrip-debuginfo-if-disabled=yes`, tell the linker to strip any debuginfo
-                // `-Zstrip-debuginfo-if-disabled=yes`, tell the linker to strip any debuginfo
+            // found when linking to get rid of symbols from libstd.
-                // found when linking to get rid of symbols from libstd.
+            if let Some(true) = self.sess.opts.debugging_opts.strip_debuginfo_if_disabled {
-                match self.sess.opts.debugging_opts.strip_debuginfo_if_disabled {
+                self.linker_arg("-S");
-                    Some(true) => { self.linker_arg("-S"); },
+            }
-                    _ => {},
-                }
-            },
-            _ => {},
         };
     }