Auto merge of #64303 - nnethercote:avoid-more-Symbol-to-string-operations, r=petrochenkov

Avoid more `Symbol`-to-string operations

These commits avoid various `Symbol`-to-string conversions, by doing more operations directly on `Symbol`s. This requires adding a few more static `Symbol`s to the binary.

r? @petrochenkov

13 files changed, 93 insertions, 81 deletions

diff --git a/src/librustc/middle/weak_lang_items.rs b/src/librustc/middle/weak_lang_items.rs
index 4fb88dadd1f..fa5fa2257db 100644
--- a/src/librustc/middle/weak_lang_items.rs
+++ b/src/librustc/middle/weak_lang_items.rs
@@ -116,8 +116,8 @@ fn verify<'tcx>(tcx: TyCtxt<'tcx>,
 }
 
 impl<'a, 'tcx> Context<'a, 'tcx> {
-    fn register(&mut self, name: &str, span: Span) {
-        $(if name == stringify!($name) {
+    fn register(&mut self, name: Symbol, span: Span) {
+        $(if name == sym::$name {
             if self.items.$name().is_none() {
                 self.items.missing.push(lang_items::$item);
             }
@@ -136,7 +136,7 @@ impl<'a, 'tcx, 'v> Visitor<'v> for Context<'a, 'tcx> {
 
     fn visit_foreign_item(&mut self, i: &hir::ForeignItem) {
         if let Some((lang_item, _)) = lang_items::extract(&i.attrs) {
-            self.register(&lang_item.as_str(), i.span);
+            self.register(lang_item, i.span);
         }
         intravisit::walk_foreign_item(self, i)
     }
diff --git a/src/librustc_codegen_llvm/back/archive.rs b/src/librustc_codegen_llvm/back/archive.rs
index e3b7cb235c6..68d3f90cd39 100644
--- a/src/librustc_codegen_llvm/back/archive.rs
+++ b/src/librustc_codegen_llvm/back/archive.rs
@@ -12,6 +12,7 @@ use crate::llvm::{self, ArchiveKind};
 use rustc_codegen_ssa::{METADATA_FILENAME, RLIB_BYTECODE_EXTENSION};
 use rustc_codegen_ssa::back::archive::{ArchiveBuilder, find_library};
 use rustc::session::Session;
+use syntax::symbol::Symbol;
 
 struct ArchiveConfig<'a> {
     pub sess: &'a Session,
@@ -109,7 +110,7 @@ impl<'a> ArchiveBuilder<'a> for LlvmArchiveBuilder<'a> {
 
     /// Adds all of the contents of a native library to this archive. This will
     /// search in the relevant locations for a library named `name`.
-    fn add_native_library(&mut self, name: &str) {
+    fn add_native_library(&mut self, name: Symbol) {
         let location = find_library(name, &self.config.lib_search_paths,
                                     self.config.sess);
         self.add_archive(&location, |_| false).unwrap_or_else(|e| {
diff --git a/src/librustc_codegen_ssa/back/archive.rs b/src/librustc_codegen_ssa/back/archive.rs
index 23d580ef08b..8d2120a345a 100644
--- a/src/librustc_codegen_ssa/back/archive.rs
+++ b/src/librustc_codegen_ssa/back/archive.rs
@@ -1,9 +1,10 @@
 use rustc::session::Session;
+use syntax::symbol::Symbol;
 
 use std::io;
 use std::path::{Path, PathBuf};
 
-pub fn find_library(name: &str, search_paths: &[PathBuf], sess: &Session)
+pub fn find_library(name: Symbol, search_paths: &[PathBuf], sess: &Session)
                     -> PathBuf {
     // On Windows, static libraries sometimes show up as libfoo.a and other
     // times show up as foo.lib
@@ -40,7 +41,7 @@ pub trait ArchiveBuilder<'a> {
         lto: bool,
         skip_objects: bool,
     ) -> io::Result<()>;
-    fn add_native_library(&mut self, name: &str);
+    fn add_native_library(&mut self, name: Symbol);
     fn update_symbols(&mut self);
 
     fn build(self);
diff --git a/src/librustc_codegen_ssa/back/command.rs b/src/librustc_codegen_ssa/back/command.rs
index 340cc772e5f..2c2ede5e189 100644
--- a/src/librustc_codegen_ssa/back/command.rs
+++ b/src/librustc_codegen_ssa/back/command.rs
@@ -8,6 +8,7 @@ use std::mem;
 use std::process::{self, Output};
 
 use rustc_target::spec::LldFlavor;
+use syntax::symbol::Symbol;
 
 #[derive(Clone)]
 pub struct Command {
@@ -49,6 +50,11 @@ impl Command {
         self
     }
 
+    pub fn sym_arg(&mut self, arg: Symbol) -> &mut Command {
+        self.arg(&arg.as_str());
+        self
+    }
+
     pub fn args<I>(&mut self, args: I) -> &mut Command
     where
         I: IntoIterator<Item: AsRef<OsStr>>,
diff --git a/src/librustc_codegen_ssa/back/link.rs b/src/librustc_codegen_ssa/back/link.rs
index 8603d61fb54..c6e0e6a1e80 100644
--- a/src/librustc_codegen_ssa/back/link.rs
+++ b/src/librustc_codegen_ssa/back/link.rs
@@ -13,6 +13,7 @@ use rustc::hir::def_id::CrateNum;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_fs_util::fix_windows_verbatim_for_gcc;
 use rustc_target::spec::{PanicStrategy, RelroLevel, LinkerFlavor};
+use syntax::symbol::Symbol;
 
 use crate::{METADATA_FILENAME, RLIB_BYTECODE_EXTENSION, CrateInfo, CodegenResults};
 use super::archive::ArchiveBuilder;
@@ -316,7 +317,7 @@ fn link_rlib<'a, B: ArchiveBuilder<'a>>(sess: &'a Session,
             NativeLibraryKind::NativeUnknown => continue,
         }
         if let Some(name) = lib.name {
-            ab.add_native_library(&name.as_str());
+            ab.add_native_library(name);
         }
     }
 
@@ -1273,15 +1274,14 @@ pub fn add_local_native_libraries(cmd: &mut dyn Linker,
     let search_path = archive_search_paths(sess);
     for lib in relevant_libs {
         let name = match lib.name {
-            Some(ref l) => l,
+            Some(l) => l,
             None => continue,
         };
         match lib.kind {
-            NativeLibraryKind::NativeUnknown => cmd.link_dylib(&name.as_str()),
-            NativeLibraryKind::NativeFramework => cmd.link_framework(&name.as_str()),
-            NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(&name.as_str()),
-            NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(&name.as_str(),
-                                                                        &search_path)
+            NativeLibraryKind::NativeUnknown => cmd.link_dylib(name),
+            NativeLibraryKind::NativeFramework => cmd.link_framework(name),
+            NativeLibraryKind::NativeStaticNobundle => cmd.link_staticlib(name),
+            NativeLibraryKind::NativeStatic => cmd.link_whole_staticlib(name, &search_path)
         }
     }
 }
@@ -1594,7 +1594,7 @@ fn add_upstream_rust_crates<'a, B: ArchiveBuilder<'a>>(cmd: &mut dyn Linker,
             cmd.include_path(&fix_windows_verbatim_for_gcc(dir));
         }
         let filestem = cratepath.file_stem().unwrap().to_str().unwrap();
-        cmd.link_rust_dylib(&unlib(&sess.target, filestem),
+        cmd.link_rust_dylib(Symbol::intern(&unlib(&sess.target, filestem)),
                             parent.unwrap_or(Path::new("")));
     }
 }
@@ -1637,22 +1637,22 @@ pub fn add_upstream_native_libraries(cmd: &mut dyn Linker,
     for &(cnum, _) in crates {
         for lib in codegen_results.crate_info.native_libraries[&cnum].iter() {
             let name = match lib.name {
-                Some(ref l) => l,
+                Some(l) => l,
                 None => continue,
             };
             if !relevant_lib(sess, &lib) {
                 continue
             }
             match lib.kind {
-                NativeLibraryKind::NativeUnknown => cmd.link_dylib(&name.as_str()),
-                NativeLibraryKind::NativeFramework => cmd.link_framework(&name.as_str()),
+                NativeLibraryKind::NativeUnknown => cmd.link_dylib(name),
+                NativeLibraryKind::NativeFramework => cmd.link_framework(name),
                 NativeLibraryKind::NativeStaticNobundle => {
                     // Link "static-nobundle" native libs only if the crate they originate from
                     // is being linked statically to the current crate.  If it's linked dynamically
                     // or is an rlib already included via some other dylib crate, the symbols from
                     // native libs will have already been included in that dylib.
                     if data[cnum.as_usize() - 1] == Linkage::Static {
-                        cmd.link_staticlib(&name.as_str())
+                        cmd.link_staticlib(name)
                     }
                 },
                 // ignore statically included native libraries here as we've
diff --git a/src/librustc_codegen_ssa/back/linker.rs b/src/librustc_codegen_ssa/back/linker.rs
index de481d22624..c42cd024926 100644
--- a/src/librustc_codegen_ssa/back/linker.rs
+++ b/src/librustc_codegen_ssa/back/linker.rs
@@ -17,6 +17,7 @@ use rustc::session::config::{self, CrateType, OptLevel, DebugInfo,
 use rustc::ty::TyCtxt;
 use rustc_target::spec::{LinkerFlavor, LldFlavor};
 use rustc_serialize::{json, Encoder};
+use syntax::symbol::Symbol;
 
 /// For all the linkers we support, and information they might
 /// need out of the shared crate context before we get rid of it.
@@ -99,13 +100,13 @@ impl LinkerInfo {
 /// used to dispatch on whether a GNU-like linker (generally `ld.exe`) or an
 /// MSVC linker (e.g., `link.exe`) is being used.
 pub trait Linker {
-    fn link_dylib(&mut self, lib: &str);
-    fn link_rust_dylib(&mut self, lib: &str, path: &Path);
-    fn link_framework(&mut self, framework: &str);
-    fn link_staticlib(&mut self, lib: &str);
+    fn link_dylib(&mut self, lib: Symbol);
+    fn link_rust_dylib(&mut self, lib: Symbol, path: &Path);
+    fn link_framework(&mut self, framework: Symbol);
+    fn link_staticlib(&mut self, lib: Symbol);
     fn link_rlib(&mut self, lib: &Path);
     fn link_whole_rlib(&mut self, lib: &Path);
-    fn link_whole_staticlib(&mut self, lib: &str, search_path: &[PathBuf]);
+    fn link_whole_staticlib(&mut self, lib: Symbol, search_path: &[PathBuf]);
     fn include_path(&mut self, path: &Path);
     fn framework_path(&mut self, path: &Path);
     fn output_filename(&mut self, path: &Path);
@@ -215,9 +216,13 @@ impl<'a> GccLinker<'a> {
 }
 
 impl<'a> Linker for GccLinker<'a> {
-    fn link_dylib(&mut self, lib: &str) { self.hint_dynamic(); self.cmd.arg(format!("-l{}", lib)); }
-    fn link_staticlib(&mut self, lib: &str) {
-        self.hint_static(); self.cmd.arg(format!("-l{}", lib));
+    fn link_dylib(&mut self, lib: Symbol) {
+        self.hint_dynamic();
+        self.cmd.arg(format!("-l{}", lib));
+    }
+    fn link_staticlib(&mut self, lib: Symbol) {
+        self.hint_static();
+        self.cmd.arg(format!("-l{}", lib));
     }
     fn link_rlib(&mut self, lib: &Path) { self.hint_static(); self.cmd.arg(lib); }
     fn include_path(&mut self, path: &Path) { self.cmd.arg("-L").arg(path); }
@@ -232,14 +237,14 @@ impl<'a> Linker for GccLinker<'a> {
     fn build_static_executable(&mut self) { self.cmd.arg("-static"); }
     fn args(&mut self, args: &[String]) { self.cmd.args(args); }
 
-    fn link_rust_dylib(&mut self, lib: &str, _path: &Path) {
+    fn link_rust_dylib(&mut self, lib: Symbol, _path: &Path) {
         self.hint_dynamic();
         self.cmd.arg(format!("-l{}", lib));
     }
 
-    fn link_framework(&mut self, framework: &str) {
+    fn link_framework(&mut self, framework: Symbol) {
         self.hint_dynamic();
-        self.cmd.arg("-framework").arg(framework);
+        self.cmd.arg("-framework").sym_arg(framework);
     }
 
     // Here we explicitly ask that the entire archive is included into the
@@ -248,7 +253,7 @@ impl<'a> Linker for GccLinker<'a> {
     // don't otherwise explicitly reference them. This can occur for
     // libraries which are just providing bindings, libraries with generic
     // functions, etc.
-    fn link_whole_staticlib(&mut self, lib: &str, search_path: &[PathBuf]) {
+    fn link_whole_staticlib(&mut self, lib: Symbol, search_path: &[PathBuf]) {
         self.hint_static();
         let target = &self.sess.target.target;
         if !target.options.is_like_osx {
@@ -539,11 +544,11 @@ impl<'a> Linker for MsvcLinker<'a> {
         }
     }
 
-    fn link_dylib(&mut self, lib: &str) {
+    fn link_dylib(&mut self, lib: Symbol) {
         self.cmd.arg(&format!("{}.lib", lib));
     }
 
-    fn link_rust_dylib(&mut self, lib: &str, path: &Path) {
+    fn link_rust_dylib(&mut self, lib: Symbol, path: &Path) {
         // When producing a dll, the MSVC linker may not actually emit a
         // `foo.lib` file if the dll doesn't actually export any symbols, so we
         // check to see if the file is there and just omit linking to it if it's
@@ -554,7 +559,7 @@ impl<'a> Linker for MsvcLinker<'a> {
         }
     }
 
-    fn link_staticlib(&mut self, lib: &str) {
+    fn link_staticlib(&mut self, lib: Symbol) {
         self.cmd.arg(&format!("{}.lib", lib));
     }
 
@@ -605,11 +610,11 @@ impl<'a> Linker for MsvcLinker<'a> {
     fn framework_path(&mut self, _path: &Path) {
         bug!("frameworks are not supported on windows")
     }
-    fn link_framework(&mut self, _framework: &str) {
+    fn link_framework(&mut self, _framework: Symbol) {
         bug!("frameworks are not supported on windows")
     }
 
-    fn link_whole_staticlib(&mut self, lib: &str, _search_path: &[PathBuf]) {
+    fn link_whole_staticlib(&mut self, lib: Symbol, _search_path: &[PathBuf]) {
         // not supported?
         self.link_staticlib(lib);
     }
@@ -740,8 +745,8 @@ impl<'a> Linker for EmLinker<'a> {
         self.cmd.arg("-L").arg(path);
     }
 
-    fn link_staticlib(&mut self, lib: &str) {
-        self.cmd.arg("-l").arg(lib);
+    fn link_staticlib(&mut self, lib: Symbol) {
+        self.cmd.arg("-l").sym_arg(lib);
     }
 
     fn output_filename(&mut self, path: &Path) {
@@ -752,12 +757,12 @@ impl<'a> Linker for EmLinker<'a> {
         self.cmd.arg(path);
     }
 
-    fn link_dylib(&mut self, lib: &str) {
+    fn link_dylib(&mut self, lib: Symbol) {
         // Emscripten always links statically
         self.link_staticlib(lib);
     }
 
-    fn link_whole_staticlib(&mut self, lib: &str, _search_path: &[PathBuf]) {
+    fn link_whole_staticlib(&mut self, lib: Symbol, _search_path: &[PathBuf]) {
         // not supported?
         self.link_staticlib(lib);
     }
@@ -767,7 +772,7 @@ impl<'a> Linker for EmLinker<'a> {
         self.link_rlib(lib);
     }
 
-    fn link_rust_dylib(&mut self, lib: &str, _path: &Path) {
+    fn link_rust_dylib(&mut self, lib: Symbol, _path: &Path) {
         self.link_dylib(lib);
     }
 
@@ -803,7 +808,7 @@ impl<'a> Linker for EmLinker<'a> {
         bug!("frameworks are not supported on Emscripten")
     }
 
-    fn link_framework(&mut self, _framework: &str) {
+    fn link_framework(&mut self, _framework: Symbol) {
         bug!("frameworks are not supported on Emscripten")
     }
 
@@ -948,12 +953,12 @@ impl<'a> WasmLd<'a> {
 }
 
 impl<'a> Linker for WasmLd<'a> {
-    fn link_dylib(&mut self, lib: &str) {
-        self.cmd.arg("-l").arg(lib);
+    fn link_dylib(&mut self, lib: Symbol) {
+        self.cmd.arg("-l").sym_arg(lib);
     }
 
-    fn link_staticlib(&mut self, lib: &str) {
-        self.cmd.arg("-l").arg(lib);
+    fn link_staticlib(&mut self, lib: Symbol) {
+        self.cmd.arg("-l").sym_arg(lib);
     }
 
     fn link_rlib(&mut self, lib: &Path) {
@@ -995,16 +1000,16 @@ impl<'a> Linker for WasmLd<'a> {
         self.cmd.args(args);
     }
 
-    fn link_rust_dylib(&mut self, lib: &str, _path: &Path) {
-        self.cmd.arg("-l").arg(lib);
+    fn link_rust_dylib(&mut self, lib: Symbol, _path: &Path) {
+        self.cmd.arg("-l").sym_arg(lib);
     }
 
-    fn link_framework(&mut self, _framework: &str) {
+    fn link_framework(&mut self, _framework: Symbol) {
         panic!("frameworks not supported")
     }
 
-    fn link_whole_staticlib(&mut self, lib: &str, _search_path: &[PathBuf]) {
-        self.cmd.arg("-l").arg(lib);
+    fn link_whole_staticlib(&mut self, lib: Symbol, _search_path: &[PathBuf]) {
+        self.cmd.arg("-l").sym_arg(lib);
     }
 
     fn link_whole_rlib(&mut self, lib: &Path) {
@@ -1162,19 +1167,19 @@ impl<'a> Linker for PtxLinker<'a> {
         ::std::mem::replace(&mut self.cmd, Command::new(""))
     }
 
-    fn link_dylib(&mut self, _lib: &str) {
+    fn link_dylib(&mut self, _lib: Symbol) {
         panic!("external dylibs not supported")
     }
 
-    fn link_rust_dylib(&mut self, _lib: &str, _path: &Path) {
+    fn link_rust_dylib(&mut self, _lib: Symbol, _path: &Path) {
         panic!("external dylibs not supported")
     }
 
-    fn link_staticlib(&mut self, _lib: &str) {
+    fn link_staticlib(&mut self, _lib: Symbol) {
         panic!("staticlibs not supported")
     }
 
-    fn link_whole_staticlib(&mut self, _lib: &str, _search_path: &[PathBuf]) {
+    fn link_whole_staticlib(&mut self, _lib: Symbol, _search_path: &[PathBuf]) {
         panic!("staticlibs not supported")
     }
 
@@ -1182,7 +1187,7 @@ impl<'a> Linker for PtxLinker<'a> {
         panic!("frameworks not supported")
     }
 
-    fn link_framework(&mut self, _framework: &str) {
+    fn link_framework(&mut self, _framework: Symbol) {
         panic!("frameworks not supported")
     }
 
diff --git a/src/librustc_incremental/assert_module_sources.rs b/src/librustc_incremental/assert_module_sources.rs
index 046fdc72270..e08eeaf8575 100644
--- a/src/librustc_incremental/assert_module_sources.rs
+++ b/src/librustc_incremental/assert_module_sources.rs
@@ -27,7 +27,7 @@ use rustc::mir::mono::CodegenUnitNameBuilder;
 use rustc::ty::TyCtxt;
 use std::collections::BTreeSet;
 use syntax::ast;
-use syntax::symbol::{Symbol, sym};
+use syntax::symbol::{InternedString, Symbol, sym};
 use rustc::ich::{ATTR_PARTITION_REUSED, ATTR_PARTITION_CODEGENED,
                  ATTR_EXPECTED_CGU_REUSE};
 
@@ -45,8 +45,8 @@ pub fn assert_module_sources(tcx: TyCtxt<'_>) {
             .collect_and_partition_mono_items(LOCAL_CRATE)
             .1
             .iter()
-            .map(|cgu| format!("{}", cgu.name()))
-            .collect::<BTreeSet<String>>();
+            .map(|cgu| *cgu.name())
+            .collect::<BTreeSet<InternedString>>();
 
         let ams = AssertModuleSource {
             tcx,
@@ -61,7 +61,7 @@ pub fn assert_module_sources(tcx: TyCtxt<'_>) {
 
 struct AssertModuleSource<'tcx> {
     tcx: TyCtxt<'tcx>,
-    available_cgus: BTreeSet<String>,
+    available_cgus: BTreeSet<InternedString>,
 }
 
 impl AssertModuleSource<'tcx> {
@@ -127,7 +127,7 @@ impl AssertModuleSource<'tcx> {
 
         debug!("mapping '{}' to cgu name '{}'", self.field(attr, MODULE), cgu_name);
 
-        if !self.available_cgus.contains(&cgu_name.as_str()[..]) {
+        if !self.available_cgus.contains(&cgu_name) {
             self.tcx.sess.span_err(attr.span,
                 &format!("no module named `{}` (mangled: {}). \
                           Available modules: {}",
@@ -135,7 +135,7 @@ impl AssertModuleSource<'tcx> {
                     cgu_name,
                     self.available_cgus
                         .iter()
-                        .cloned()
+                        .map(|cgu| cgu.as_str().to_string())
                         .collect::<Vec<_>>()
                         .join(", ")));
         }
diff --git a/src/librustc_metadata/native_libs.rs b/src/librustc_metadata/native_libs.rs
index 66d676b7747..ada1a8c615d 100644
--- a/src/librustc_metadata/native_libs.rs
+++ b/src/librustc_metadata/native_libs.rs
@@ -8,7 +8,7 @@ use rustc_target::spec::abi::Abi;
 use syntax::attr;
 use syntax::source_map::Span;
 use syntax::feature_gate::{self, GateIssue};
-use syntax::symbol::{Symbol, sym};
+use syntax::symbol::{kw, sym, Symbol};
 use syntax::{span_err, struct_span_err};
 
 pub fn collect(tcx: TyCtxt<'_>) -> Vec<NativeLibrary> {
@@ -132,7 +132,7 @@ impl ItemLikeVisitor<'tcx> for Collector<'tcx> {
 
 impl Collector<'tcx> {
     fn register_native_lib(&mut self, span: Option<Span>, lib: NativeLibrary) {
-        if lib.name.as_ref().map(|s| s.as_str().is_empty()).unwrap_or(false) {
+        if lib.name.as_ref().map(|&s| s == kw::Invalid).unwrap_or(false) {
             match span {
                 Some(span) => {
                     struct_span_err!(self.tcx.sess, span, E0454,
diff --git a/src/librustc_mir/const_eval.rs b/src/librustc_mir/const_eval.rs
index db679024dc5..3e02497947a 100644
--- a/src/librustc_mir/const_eval.rs
+++ b/src/librustc_mir/const_eval.rs
@@ -383,7 +383,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
             return Ok(());
         }
         // An intrinsic that we do not support
-        let intrinsic_name = &ecx.tcx.item_name(instance.def_id()).as_str()[..];
+        let intrinsic_name = ecx.tcx.item_name(instance.def_id());
         Err(
             ConstEvalError::NeedsRfc(format!("calling intrinsic `{}`", intrinsic_name)).into()
         )
diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs
index e9ca0f3d978..09e6b769003 100644
--- a/src/librustc_typeck/astconv.rs
+++ b/src/librustc_typeck/astconv.rs
@@ -1462,7 +1462,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         span: Span,
         type_str: &str,
         trait_str: &str,
-        name: &str,
+        name: ast::Name,
     ) {
         let mut err = struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type");
         if let (Some(_), Ok(snippet)) = (
@@ -1689,7 +1689,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         span,
                         &qself_ty.to_string(),
                         "Trait",
-                        &assoc_ident.as_str(),
+                        assoc_ident.name,
                     );
                 }
                 return Err(ErrorReported);
@@ -1762,7 +1762,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 span,
                 "Type",
                 &path_str,
-                &item_segment.ident.as_str(),
+                item_segment.ident.name,
             );
             return tcx.types.err;
         };
diff --git a/src/librustdoc/clean/cfg.rs b/src/librustdoc/clean/cfg.rs
index b9b3e621bb7..c3092cea983 100644
--- a/src/librustdoc/clean/cfg.rs
+++ b/src/librustdoc/clean/cfg.rs
@@ -81,10 +81,10 @@ impl Cfg {
             },
             MetaItemKind::List(ref items) => {
                 let mut sub_cfgs = items.iter().map(Cfg::parse_nested);
-                match &*name.as_str() {
-                    "all" => sub_cfgs.fold(Ok(Cfg::True), |x, y| Ok(x? & y?)),
-                    "any" => sub_cfgs.fold(Ok(Cfg::False), |x, y| Ok(x? | y?)),
-                    "not" => if sub_cfgs.len() == 1 {
+                match name {
+                    sym::all => sub_cfgs.fold(Ok(Cfg::True), |x, y| Ok(x? & y?)),
+                    sym::any => sub_cfgs.fold(Ok(Cfg::False), |x, y| Ok(x? | y?)),
+                    sym::not => if sub_cfgs.len() == 1 {
                         Ok(!sub_cfgs.next().unwrap()?)
                     } else {
                         Err(InvalidCfgError {
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 38eff43bad2..ae70fdc530b 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1039,7 +1039,7 @@ impl GenericBound {
     fn maybe_sized(cx: &DocContext<'_>) -> GenericBound {
         let did = cx.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
         let empty = cx.tcx.intern_substs(&[]);
-        let path = external_path(cx, &cx.tcx.item_name(did).as_str(),
+        let path = external_path(cx, cx.tcx.item_name(did),
             Some(did), false, vec![], empty);
         inline::record_extern_fqn(cx, did, TypeKind::Trait);
         GenericBound::TraitBound(PolyTrait {
@@ -1138,13 +1138,13 @@ fn external_generic_args(
 
 // trait_did should be set to a trait's DefId if called on a TraitRef, in order to sugar
 // from Fn<(A, B,), C> to Fn(A, B) -> C
-fn external_path(cx: &DocContext<'_>, name: &str, trait_did: Option<DefId>, has_self: bool,
+fn external_path(cx: &DocContext<'_>, name: Symbol, trait_did: Option<DefId>, has_self: bool,
                  bindings: Vec<TypeBinding>, substs: SubstsRef<'_>) -> Path {
     Path {
         global: false,
         res: Res::Err,
         segments: vec![PathSegment {
-            name: name.to_string(),
+            name: name.as_str().to_string(),
             args: external_generic_args(cx, trait_did, has_self, bindings, substs)
         }],
     }
@@ -1154,7 +1154,7 @@ impl<'a, 'tcx> Clean<GenericBound> for (&'a ty::TraitRef<'tcx>, Vec<TypeBinding>
     fn clean(&self, cx: &DocContext<'_>) -> GenericBound {
         let (trait_ref, ref bounds) = *self;
         inline::record_extern_fqn(cx, trait_ref.def_id, TypeKind::Trait);
-        let path = external_path(cx, &cx.tcx.item_name(trait_ref.def_id).as_str(),
+        let path = external_path(cx, cx.tcx.item_name(trait_ref.def_id),
                                  Some(trait_ref.def_id), true, bounds.clone(), trait_ref.substs);
 
         debug!("ty::TraitRef\n  subst: {:?}\n", trait_ref.substs);
@@ -3089,8 +3089,7 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
                     AdtKind::Enum => TypeKind::Enum,
                 };
                 inline::record_extern_fqn(cx, did, kind);
-                let path = external_path(cx, &cx.tcx.item_name(did).as_str(),
-                                         None, false, vec![], substs);
+                let path = external_path(cx, cx.tcx.item_name(did), None, false, vec![], substs);
                 ResolvedPath {
                     path,
                     param_names: None,
@@ -3100,7 +3099,7 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
             }
             ty::Foreign(did) => {
                 inline::record_extern_fqn(cx, did, TypeKind::Foreign);
-                let path = external_path(cx, &cx.tcx.item_name(did).as_str(),
+                let path = external_path(cx, cx.tcx.item_name(did),
                                          None, false, vec![], InternalSubsts::empty());
                 ResolvedPath {
                     path: path,
@@ -3129,7 +3128,7 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
                 reg.clean(cx).map(|b| param_names.push(GenericBound::Outlives(b)));
                 for did in dids {
                     let empty = cx.tcx.intern_substs(&[]);
-                    let path = external_path(cx, &cx.tcx.item_name(did).as_str(),
+                    let path = external_path(cx, cx.tcx.item_name(did),
                         Some(did), false, vec![], empty);
                     inline::record_extern_fqn(cx, did, TypeKind::Trait);
                     let bound = GenericBound::TraitBound(PolyTrait {
@@ -3154,7 +3153,7 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
                     });
                 }
 
-                let path = external_path(cx, &cx.tcx.item_name(did).as_str(), Some(did),
+                let path = external_path(cx, cx.tcx.item_name(did), Some(did),
                     false, bindings, substs);
                 ResolvedPath {
                     path,
diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index 6f1eb039442..acc41b7c13b 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -423,7 +423,7 @@ pub fn make_test(s: &str,
                 Ok(Some(item)) => {
                     if !found_main {
                         if let ast::ItemKind::Fn(..) = item.node {
-                            if item.ident.as_str() == "main" {
+                            if item.ident.name == sym::main {
                                 found_main = true;
                             }
                         }