Auto merge of #91957 - nnethercote:rm-SymbolStr, r=oli-obk

Remove `SymbolStr`

This was originally proposed in https://github.com/rust-lang/rust/pull/74554#discussion_r466203544. As well as removing the icky `SymbolStr` type, it allows the removal of a lot of `&` and `*` occurrences.

Best reviewed one commit at a time.

r? `@oli-obk`

compiler/rustc_ast/src/util/literal.rs

@@ -35,12 +35,12 @@ impl LitKind {
                 LitKind::Bool(symbol == kw::True)
             }
             token::Byte => {
-                return unescape_byte(&symbol.as_str())
+                return unescape_byte(symbol.as_str())
                     .map(LitKind::Byte)
                     .map_err(|_| LitError::LexerError);
             }
             token::Char => {
-                return unescape_char(&symbol.as_str())
+                return unescape_char(symbol.as_str())
                     .map(LitKind::Char)
                     .map_err(|_| LitError::LexerError);
             }

compiler/rustc_ast_lowering/src/item.rs

@@ -1278,7 +1278,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     }
 
     pub(super) fn lower_abi(&mut self, abi: StrLit) -> abi::Abi {
-        abi::lookup(&abi.symbol_unescaped.as_str()).unwrap_or_else(|| {
+        abi::lookup(abi.symbol_unescaped.as_str()).unwrap_or_else(|| {
             self.error_on_invalid_abi(abi);
             abi::Abi::Rust
         })

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -580,8 +580,7 @@ impl<'a> AstValidator<'a> {
 
     /// An item in `extern { ... }` cannot use non-ascii identifier.
     fn check_foreign_item_ascii_only(&self, ident: Ident) {
-        let symbol_str = ident.as_str();
+        if !ident.as_str().is_ascii() {
-        if !symbol_str.is_ascii() {
             let n = 83942;
             self.err_handler()
                 .struct_span_err(

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -61,7 +61,7 @@ impl<'a> PostExpansionVisitor<'a> {
     fn check_abi(&self, abi: ast::StrLit) {
         let ast::StrLit { symbol_unescaped, span, .. } = abi;
 
-        match &*symbol_unescaped.as_str() {
+        match symbol_unescaped.as_str() {
             // Stable
             "Rust" | "C" | "cdecl" | "stdcall" | "fastcall" | "aapcs" | "win64" | "sysv64"
             | "system" => {}

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -204,7 +204,7 @@ pub fn literal_to_string(lit: token::Lit) -> String {
     };
 
     if let Some(suffix) = suffix {
-        out.push_str(&suffix.as_str())
+        out.push_str(suffix.as_str())
     }
 
     out
@@ -384,7 +384,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
     }
 
     fn print_symbol(&mut self, sym: Symbol, style: ast::StrStyle) {
-        self.print_string(&sym.as_str(), style);
+        self.print_string(sym.as_str(), style);
     }
 
     fn print_inner_attributes(&mut self, attrs: &[ast::Attribute]) {

compiler/rustc_attr/src/builtin.rs

@@ -236,7 +236,7 @@ where
 
                                     // These unwraps are safe because `get` ensures the meta item
                                     // is a name/value pair string literal.
-                                    issue_num = match &*issue.unwrap().as_str() {
+                                    issue_num = match issue.unwrap().as_str() {
                                         "none" => None,
                                         issue => {
                                             let emit_diag = |msg: &str| {
@@ -301,7 +301,7 @@ where
 
                     match (feature, reason, issue) {
                         (Some(feature), reason, Some(_)) => {
-                            if !rustc_lexer::is_ident(&feature.as_str()) {
+                            if !rustc_lexer::is_ident(feature.as_str()) {
                                 handle_errors(
                                     &sess.parse_sess,
                                     attr.span,
@@ -535,7 +535,7 @@ pub fn eval_condition(
                     return false;
                 }
             };
-            let min_version = match parse_version(&min_version.as_str(), false) {
+            let min_version = match parse_version(min_version.as_str(), false) {
                 Some(ver) => ver,
                 None => {
                     sess.span_diagnostic

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -416,7 +416,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             tcx,
                             generics,
                             &mut err,
-                            &param.name.as_str(),
+                            param.name.as_str(),
                             "Copy",
                             None,
                         );

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -206,7 +206,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             {
                 let local_info = &self.body.local_decls[local].local_info;
                 if let Some(box LocalInfo::StaticRef { def_id, .. }) = *local_info {
-                    buf.push_str(&self.infcx.tcx.item_name(def_id).as_str());
+                    buf.push_str(self.infcx.tcx.item_name(def_id).as_str());
                 } else {
                     unreachable!();
                 }
@@ -318,7 +318,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let decl = &self.body.local_decls[local];
         match self.local_names[local] {
             Some(name) if !decl.from_compiler_desugaring() => {
-                buf.push_str(&name.as_str());
+                buf.push_str(name.as_str());
                 Ok(())
             }
             _ => Err(()),

compiler/rustc_builtin_macros/src/asm.rs

@@ -573,7 +573,7 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
             template_snippet.as_ref().map(|s| Symbol::intern(s)),
             template_sp,
         ));
-        let template_str = &template_str.as_str();
+        let template_str = template_str.as_str();
 
         if let Some(InlineAsmArch::X86 | InlineAsmArch::X86_64) = ecx.sess.asm_arch {
             let find_span = |needle: &str| -> Span {

compiler/rustc_builtin_macros/src/concat.rs

@@ -21,7 +21,7 @@ pub fn expand_concat(
         match e.kind {
             ast::ExprKind::Lit(ref lit) => match lit.kind {
                 ast::LitKind::Str(ref s, _) | ast::LitKind::Float(ref s, _) => {
-                    accumulator.push_str(&s.as_str());
+                    accumulator.push_str(s.as_str());
                 }
                 ast::LitKind::Char(c) => {
                     accumulator.push(c);

compiler/rustc_builtin_macros/src/concat_idents.rs

@@ -29,7 +29,7 @@ pub fn expand_concat_idents<'cx>(
         } else {
             if let TokenTree::Token(token) = e {
                 if let Some((ident, _)) = token.ident() {
-                    res_str.push_str(&ident.name.as_str());
+                    res_str.push_str(ident.name.as_str());
                     continue;
                 }
             }

compiler/rustc_builtin_macros/src/derive.rs

@@ -121,7 +121,7 @@ fn report_bad_target(sess: &Session, item: &Annotatable, span: Span) -> bool {
 
 fn report_unexpected_literal(sess: &Session, lit: &ast::Lit) {
     let help_msg = match lit.token.kind {
-        token::Str if rustc_lexer::is_ident(&lit.token.symbol.as_str()) => {
+        token::Str if rustc_lexer::is_ident(lit.token.symbol.as_str()) => {
             format!("try using `#[derive({})]`", lit.token.symbol)
         }
         _ => "for example, write `#[derive(Debug)]` for `Debug`".to_string(),

compiler/rustc_builtin_macros/src/env.rs

@@ -80,11 +80,11 @@ pub fn expand_env<'cx>(
     }
 
     let sp = cx.with_def_site_ctxt(sp);
-    let value = env::var(&*var.as_str()).ok().as_deref().map(Symbol::intern);
+    let value = env::var(var.as_str()).ok().as_deref().map(Symbol::intern);
     cx.sess.parse_sess.env_depinfo.borrow_mut().insert((var, value));
     let e = match value {
         None => {
-            cx.span_err(sp, &msg.as_str());
+            cx.span_err(sp, msg.as_str());
             return DummyResult::any(sp);
         }
         Some(value) => cx.expr_str(sp, value),

compiler/rustc_builtin_macros/src/format.rs

@@ -955,7 +955,7 @@ pub fn expand_preparsed_format_args(
         ast::StrStyle::Raw(raw) => Some(raw as usize),
     };
 
-    let fmt_str = &fmt_str.as_str(); // for the suggestions below
+    let fmt_str = fmt_str.as_str(); // for the suggestions below
     let fmt_snippet = ecx.source_map().span_to_snippet(fmt_sp).ok();
     let mut parser = parse::Parser::new(
         fmt_str,

compiler/rustc_codegen_cranelift/src/constant.rs

@@ -369,7 +369,7 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
             TodoItem::Static(def_id) => {
                 //println!("static {:?}", def_id);
 
-                let section_name = tcx.codegen_fn_attrs(def_id).link_section.map(|s| s.as_str());
+                let section_name = tcx.codegen_fn_attrs(def_id).link_section;
 
                 let alloc = tcx.eval_static_initializer(def_id).unwrap();
 
@@ -388,6 +388,7 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
 
         if let Some(section_name) = section_name {
             let (segment_name, section_name) = if tcx.sess.target.is_like_osx {
+                let section_name = section_name.as_str();
                 if let Some(names) = section_name.split_once(',') {
                     names
                 } else {
@@ -397,7 +398,7 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
                     ));
                 }
             } else {
-                ("", &*section_name)
+                ("", section_name.as_str())
             };
             data_ctx.set_segment_section(segment_name, section_name);
         }

compiler/rustc_codegen_cranelift/src/driver/aot.rs

@@ -84,7 +84,7 @@ fn reuse_workproduct_for_cgu(
     let work_product = cgu.work_product(tcx);
     if let Some(saved_file) = &work_product.saved_file {
         let obj_out =
-            tcx.output_filenames(()).temp_path(OutputType::Object, Some(&cgu.name().as_str()));
+            tcx.output_filenames(()).temp_path(OutputType::Object, Some(cgu.name().as_str()));
         object = Some(obj_out.clone());
         let source_file = rustc_incremental::in_incr_comp_dir_sess(&tcx.sess, &saved_file);
         if let Err(err) = rustc_fs_util::link_or_copy(&source_file, &obj_out) {
@@ -176,7 +176,7 @@ fn module_codegen(
         )
     });
 
-    codegen_global_asm(tcx, &cgu.name().as_str(), &cx.global_asm);
+    codegen_global_asm(tcx, cgu.name().as_str(), &cx.global_asm);
 
     codegen_result
 }
@@ -207,7 +207,7 @@ pub(crate) fn run_aot(
         cgus.iter()
             .map(|cgu| {
                 let cgu_reuse = determine_cgu_reuse(tcx, cgu);
-                tcx.sess.cgu_reuse_tracker.set_actual_reuse(&cgu.name().as_str(), cgu_reuse);
+                tcx.sess.cgu_reuse_tracker.set_actual_reuse(cgu.name().as_str(), cgu_reuse);
 
                 match cgu_reuse {
                     _ if backend_config.disable_incr_cache => {}

compiler/rustc_codegen_gcc/src/common.rs

@@ -33,7 +33,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
             return value;
         }
 
-        let global = self.global_string(&*symbol.as_str());
+        let global = self.global_string(symbol.as_str());
 
         self.const_cstr_cache.borrow_mut().insert(symbol, global);
         global

compiler/rustc_codegen_gcc/src/declare.rs

@@ -17,7 +17,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
                 global.set_tls_model(self.tls_model);
             }
             if let Some(link_section) = link_section {
-                global.set_link_section(&link_section.as_str());
+                global.set_link_section(link_section.as_str());
             }
             global
         }
@@ -53,7 +53,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
             global.set_tls_model(self.tls_model);
         }
         if let Some(link_section) = link_section {
-            global.set_link_section(&link_section.as_str());
+            global.set_link_section(link_section.as_str());
         }
         let global_address = global.get_address(None);
         self.globals.borrow_mut().insert(name.to_string(), global_address);

compiler/rustc_codegen_gcc/src/intrinsic/mod.rs

@@ -88,7 +88,7 @@ impl<'a, 'gcc, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
         let arg_tys = sig.inputs();
         let ret_ty = sig.output();
         let name = tcx.item_name(def_id);
-        let name_str = &*name.as_str();
+        let name_str = name.as_str();
 
         let llret_ty = self.layout_of(ret_ty).gcc_type(self, true);
         let result = PlaceRef::new_sized(llresult, fn_abi.ret.layout);

compiler/rustc_codegen_gcc/src/intrinsic/simd.rs

@@ -52,7 +52,7 @@ pub fn generic_simd_intrinsic<'a, 'gcc, 'tcx>(bx: &mut Builder<'a, 'gcc, 'tcx>,
     let sig =
         tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), callee_ty.fn_sig(tcx));
     let arg_tys = sig.inputs();
-    let name_str = &*name.as_str();
+    let name_str = name.as_str();
 
     // every intrinsic below takes a SIMD vector as its first argument
     require_simd!(arg_tys[0], "input");

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -326,7 +326,7 @@ pub fn from_fn_attrs<'ll, 'tcx>(
         .target_features
         .iter()
         .flat_map(|f| {
-            let feature = &f.as_str();
+            let feature = f.as_str();
             llvm_util::to_llvm_feature(cx.tcx.sess, feature)
                 .into_iter()
                 .map(|f| format!("+{}", f))
@@ -351,7 +351,7 @@ pub fn from_fn_attrs<'ll, 'tcx>(
 
             let name =
                 codegen_fn_attrs.link_name.unwrap_or_else(|| cx.tcx.item_name(instance.def_id()));
-            let name = CString::new(&name.as_str()[..]).unwrap();
+            let name = CString::new(name.as_str()).unwrap();
             llvm::AddFunctionAttrStringValue(
                 llfn,
                 llvm::AttributePlace::Function,

compiler/rustc_codegen_llvm/src/base.rs

@@ -79,7 +79,7 @@ pub fn compile_codegen_unit(tcx: TyCtxt<'_>, cgu_name: Symbol) -> (ModuleCodegen
             &[cgu_name.to_string(), cgu.size_estimate().to_string()],
         );
         // Instantiate monomorphizations without filling out definitions yet...
-        let llvm_module = ModuleLlvm::new(tcx, &cgu_name.as_str());
+        let llvm_module = ModuleLlvm::new(tcx, cgu_name.as_str());
         {
             let cx = CodegenCx::new(tcx, cgu, &llvm_module);
             let mono_items = cx.codegen_unit.items_in_deterministic_order(cx.tcx);
@@ -143,7 +143,7 @@ pub fn set_link_section(llval: &Value, attrs: &CodegenFnAttrs) {
         None => return,
     };
     unsafe {
-        let buf = SmallCStr::new(&sect.as_str());
+        let buf = SmallCStr::new(sect.as_str());
         llvm::LLVMSetSection(llval, buf.as_ptr());
     }
 }

compiler/rustc_codegen_llvm/src/context.rs

@@ -320,7 +320,7 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
 
         let dbg_cx = if tcx.sess.opts.debuginfo != DebugInfo::None {
             let dctx = debuginfo::CrateDebugContext::new(llmod);
-            debuginfo::metadata::compile_unit_metadata(tcx, &codegen_unit.name().as_str(), &dctx);
+            debuginfo::metadata::compile_unit_metadata(tcx, codegen_unit.name().as_str(), &dctx);
             Some(dctx)
         } else {
             None

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -1037,7 +1037,7 @@ pub fn compile_unit_metadata<'ll, 'tcx>(
 ) -> &'ll DIDescriptor {
     let mut name_in_debuginfo = match tcx.sess.local_crate_source_file {
         Some(ref path) => path.clone(),
-        None => PathBuf::from(&*tcx.crate_name(LOCAL_CRATE).as_str()),
+        None => PathBuf::from(tcx.crate_name(LOCAL_CRATE).as_str()),
     };
 
     // To avoid breaking split DWARF, we need to ensure that each codegen unit
@@ -1371,7 +1371,7 @@ fn closure_saved_names_of_captured_variables(tcx: TyCtxt<'_>, def_id: DefId) ->
                 _ => return None,
             };
             let prefix = if is_ref { "_ref__" } else { "" };
-            Some(prefix.to_owned() + &var.name.as_str())
+            Some(prefix.to_owned() + var.name.as_str())
         })
         .collect::<Vec<_>>()
 }
@@ -1949,7 +1949,7 @@ enum VariantInfo<'a, 'tcx> {
 impl<'tcx> VariantInfo<'_, 'tcx> {
     fn map_struct_name<R>(&self, f: impl FnOnce(&str) -> R) -> R {
         match self {
-            VariantInfo::Adt(variant) => f(&variant.ident.as_str()),
+            VariantInfo::Adt(variant) => f(variant.ident.as_str()),
             VariantInfo::Generator { variant_index, .. } => {
                 f(&GeneratorSubsts::variant_name(*variant_index))
             }
@@ -2114,8 +2114,8 @@ fn prepare_enum_metadata<'ll, 'tcx>(
                 let item_name;
                 let discriminant_name = match enum_type.kind() {
                     ty::Adt(..) => {
-                        item_name = tcx.item_name(enum_def_id).as_str();
+                        item_name = tcx.item_name(enum_def_id);
-                        &*item_name
+                        item_name.as_str()
                     }
                     ty::Generator(..) => enum_name.as_str(),
                     _ => bug!(),
@@ -2448,7 +2448,7 @@ fn compute_type_parameters<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, ty: Ty<'tcx>) -
                             cx.tcx.normalize_erasing_regions(ParamEnv::reveal_all(), ty);
                         let actual_type_metadata =
                             type_metadata(cx, actual_type, rustc_span::DUMMY_SP);
-                        let name = &name.as_str();
+                        let name = name.as_str();
                         Some(unsafe {
                             Some(llvm::LLVMRustDIBuilderCreateTemplateTypeParameter(
                                 DIB(cx),
@@ -2590,7 +2590,8 @@ pub fn create_global_var_metadata<'ll>(cx: &CodegenCx<'ll, '_>, def_id: DefId, g
     let is_local_to_unit = is_node_local_to_unit(cx, def_id);
     let variable_type = Instance::mono(cx.tcx, def_id).ty(cx.tcx, ty::ParamEnv::reveal_all());
     let type_metadata = type_metadata(cx, variable_type, span);
-    let var_name = tcx.item_name(def_id).as_str();
+    let var_name = tcx.item_name(def_id);
+    let var_name = var_name.as_str();
     let linkage_name = mangled_name_of_instance(cx, Instance::mono(tcx, def_id)).name;
     // When empty, linkage_name field is omitted,
     // which is what we want for no_mangle statics

compiler/rustc_codegen_ssa/src/back/command.rs

@@ -48,7 +48,7 @@ impl Command {
     }
 
     pub fn sym_arg(&mut self, arg: Symbol) -> &mut Command {
-        self.arg(&*arg.as_str());
+        self.arg(arg.as_str());
         self
     }
 

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -88,7 +88,7 @@ pub fn link_binary<'a, B: ArchiveBuilder<'a>>(
                 sess,
                 crate_type,
                 outputs,
-                &codegen_results.crate_info.local_crate_name.as_str(),
+                codegen_results.crate_info.local_crate_name.as_str(),
             );
             match crate_type {
                 CrateType::Rlib => {

compiler/rustc_codegen_ssa/src/base.rs

@@ -672,7 +672,7 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
         }
 
         let cgu_reuse = cgu_reuse[i];
-        tcx.sess.cgu_reuse_tracker.set_actual_reuse(&cgu.name().as_str(), cgu_reuse);
+        tcx.sess.cgu_reuse_tracker.set_actual_reuse(cgu.name().as_str(), cgu_reuse);
 
         match cgu_reuse {
             CguReuse::No => {

compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs

@@ -516,7 +516,7 @@ fn push_unqualified_item_name(
 ) {
     match disambiguated_data.data {
         DefPathData::CrateRoot => {
-            output.push_str(&tcx.crate_name(def_id.krate).as_str());
+            output.push_str(tcx.crate_name(def_id.krate).as_str());
         }
         DefPathData::ClosureExpr if tcx.generator_kind(def_id).is_some() => {
             // Generators look like closures, but we want to treat them differently
@@ -529,7 +529,7 @@ fn push_unqualified_item_name(
         }
         _ => match disambiguated_data.data.name() {
             DefPathDataName::Named(name) => {
-                output.push_str(&name.as_str());
+                output.push_str(name.as_str());
             }
             DefPathDataName::Anon { namespace } => {
                 if cpp_like_names(tcx) {

compiler/rustc_codegen_ssa/src/mir/intrinsic.rs

@@ -68,7 +68,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         let arg_tys = sig.inputs();
         let ret_ty = sig.output();
         let name = bx.tcx().item_name(def_id);
-        let name_str = &*name.as_str();
+        let name_str = name.as_str();
 
         let llret_ty = bx.backend_type(bx.layout_of(ret_ty));
         let result = PlaceRef::new_sized(llresult, fn_abi.ret.layout);
@@ -375,7 +375,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 use crate::common::AtomicOrdering::*;
                 use crate::common::{AtomicRmwBinOp, SynchronizationScope};
 
-                let split: Vec<&str> = name_str.split('_').collect();
+                let split: Vec<_> = name_str.split('_').collect();
 
                 let is_cxchg = split[1] == "cxchg" || split[1] == "cxchgweak";
                 let (order, failorder) = match split.len() {

compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs

@@ -82,7 +82,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     ) -> MPlaceTy<'tcx, M::PointerTag> {
         let loc_details = &self.tcx.sess.opts.debugging_opts.location_detail;
         let file = if loc_details.file {
-            self.allocate_str(&filename.as_str(), MemoryKind::CallerLocation, Mutability::Not)
+            self.allocate_str(filename.as_str(), MemoryKind::CallerLocation, Mutability::Not)
         } else {
             // FIXME: This creates a new allocation each time. It might be preferable to
             // perform this allocation only once, and re-use the `MPlaceTy`.

compiler/rustc_const_eval/src/interpret/intrinsics/type_name.rs

@@ -88,7 +88,7 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
     }
 
     fn path_crate(mut self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
-        self.path.push_str(&self.tcx.crate_name(cnum).as_str());
+        self.path.push_str(self.tcx.crate_name(cnum).as_str());
         Ok(self)
     }
 

compiler/rustc_expand/src/config.rs

@@ -171,7 +171,7 @@ fn get_features(
             }
 
             if let Some(allowed) = sess.opts.debugging_opts.allow_features.as_ref() {
-                if allowed.iter().all(|f| name.as_str() != *f) {
+                if allowed.iter().all(|f| name.as_str() != f) {
                     struct_span_err!(
                         span_handler,
                         mi.span(),

compiler/rustc_expand/src/module.rs

@@ -103,10 +103,10 @@ crate fn mod_dir_path(
             if let DirOwnership::Owned { relative } = &mut dir_ownership {
                 if let Some(ident) = relative.take() {
                     // Remove the relative offset.
-                    dir_path.push(&*ident.as_str());
+                    dir_path.push(ident.as_str());
                 }
             }
-            dir_path.push(&*ident.as_str());
+            dir_path.push(ident.as_str());
 
             (dir_path, dir_ownership)
         }
@@ -170,8 +170,8 @@ fn mod_file_path_from_attr(
 ) -> Option<PathBuf> {
     // Extract path string from first `#[path = "path_string"]` attribute.
     let first_path = attrs.iter().find(|at| at.has_name(sym::path))?;
-    let path_string = match first_path.value_str() {
+    let path_sym = match first_path.value_str() {
-        Some(s) => s.as_str(),
+        Some(s) => s,
         None => {
             // This check is here mainly to catch attempting to use a macro,
             // such as #[path = concat!(...)]. This isn't currently supported
@@ -189,14 +189,16 @@ fn mod_file_path_from_attr(
         }
     };
 
+    let path_str = path_sym.as_str();
+
     // On windows, the base path might have the form
     // `\\?\foo\bar` in which case it does not tolerate
     // mixed `/` and `\` separators, so canonicalize
     // `/` to `\`.
     #[cfg(windows)]
-    let path_string = path_string.replace("/", "\\");
+    let path_str = path_str.replace("/", "\\");
 
-    Some(dir_path.join(&*path_string))
+    Some(dir_path.join(path_str))
 }
 
 /// Returns a path to a module.

compiler/rustc_expand/src/proc_macro_server.rs

@@ -331,9 +331,9 @@ pub struct Ident {
 
 impl Ident {
     fn new(sess: &ParseSess, sym: Symbol, is_raw: bool, span: Span) -> Ident {
-        let sym = nfc_normalize(&sym.as_str());
+        let sym = nfc_normalize(sym.as_str());
         let string = sym.as_str();
-        if !rustc_lexer::is_ident(&string) {
+        if !rustc_lexer::is_ident(string) {
             panic!("`{:?}` is not a valid identifier", string)
         }
         if is_raw && !sym.can_be_raw() {

compiler/rustc_hir/src/definitions.rs

@@ -173,7 +173,7 @@ impl DisambiguatedDefPathData {
                 if verbose && self.disambiguator != 0 {
                     write!(writer, "{}#{}", name, self.disambiguator)
                 } else {
-                    writer.write_str(&name.as_str())
+                    writer.write_str(name.as_str())
                 }
             }
             DefPathDataName::Anon { namespace } => {
@@ -499,7 +499,7 @@ impl DefPathData {
 impl fmt::Display for DefPathData {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self.name() {
-            DefPathDataName::Named(name) => f.write_str(&name.as_str()),
+            DefPathDataName::Named(name) => f.write_str(name.as_str()),
             // FIXME(#70334): this will generate legacy {{closure}}, {{impl}}, etc
             DefPathDataName::Anon { namespace } => write!(f, "{{{{{}}}}}", namespace),
         }

compiler/rustc_incremental/src/assert_dep_graph.rs

@@ -131,7 +131,7 @@ impl<'tcx> IfThisChanged<'tcx> {
                         DepNode::from_def_path_hash(self.tcx, def_path_hash, DepKind::hir_owner)
                     }
                     Some(n) => {
-                        match DepNode::from_label_string(self.tcx, &n.as_str(), def_path_hash) {
+                        match DepNode::from_label_string(self.tcx, n.as_str(), def_path_hash) {
                             Ok(n) => n,
                             Err(()) => {
                                 self.tcx.sess.span_fatal(
@@ -147,7 +147,7 @@ impl<'tcx> IfThisChanged<'tcx> {
                 let dep_node_interned = self.argument(attr);
                 let dep_node = match dep_node_interned {
                     Some(n) => {
-                        match DepNode::from_label_string(self.tcx, &n.as_str(), def_path_hash) {
+                        match DepNode::from_label_string(self.tcx, n.as_str(), def_path_hash) {
                             Ok(n) => n,
                             Err(()) => {
                                 self.tcx.sess.span_fatal(

compiler/rustc_incremental/src/assert_module_sources.rs

@@ -124,7 +124,7 @@ impl<'tcx> AssertModuleSource<'tcx> {
 
         debug!("mapping '{}' to cgu name '{}'", self.field(attr, sym::module), cgu_name);
 
-        if !self.available_cgus.contains(&*cgu_name.as_str()) {
+        if !self.available_cgus.contains(cgu_name.as_str()) {
             self.tcx.sess.span_err(
                 attr.span,
                 &format!(

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -2252,8 +2252,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                             .map(|p| p.name.as_str()),
                     );
                 }
-                let lts = lts_names.iter().map(|s| -> &str { &*s }).collect::<Vec<_>>();
+                possible.find(|candidate| !lts_names.contains(&&candidate[..]))
-                possible.find(|candidate| !lts.contains(&candidate.as_str()))
             })
             .unwrap_or("'lt".to_string());
         let add_lt_sugg = generics

compiler/rustc_interface/src/passes.rs

@@ -324,7 +324,7 @@ pub fn configure_and_expand(
         let crate_attrs = krate.attrs.clone();
         let extern_mod_loaded = |ident: Ident, attrs, items, span| {
             let krate = ast::Crate { attrs, items, span, is_placeholder: None };
-            pre_expansion_lint(sess, lint_store, &krate, &crate_attrs, &ident.name.as_str());
+            pre_expansion_lint(sess, lint_store, &krate, &crate_attrs, ident.name.as_str());
             (krate.attrs, krate.items)
         };
         let mut ecx = ExtCtxt::new(sess, cfg, resolver, Some(&extern_mod_loaded));
@@ -631,7 +631,7 @@ fn write_out_deps(
         // (e.g. accessed in proc macros).
         let file_depinfo = sess.parse_sess.file_depinfo.borrow();
         let extra_tracked_files = file_depinfo.iter().map(|path_sym| {
-            let path = PathBuf::from(&*path_sym.as_str());
+            let path = PathBuf::from(path_sym.as_str());
             let file = FileName::from(path);
             escape_dep_filename(&file.prefer_local().to_string())
         });
@@ -1049,8 +1049,8 @@ fn encode_and_write_metadata(
 
     let need_metadata_file = tcx.sess.opts.output_types.contains_key(&OutputType::Metadata);
     if need_metadata_file {
-        let crate_name = &tcx.crate_name(LOCAL_CRATE).as_str();
+        let crate_name = tcx.crate_name(LOCAL_CRATE);
-        let out_filename = filename_for_metadata(tcx.sess, crate_name, outputs);
+        let out_filename = filename_for_metadata(tcx.sess, crate_name.as_str(), outputs);
         // To avoid races with another rustc process scanning the output directory,
         // we need to write the file somewhere else and atomically move it to its
         // final destination, with an `fs::rename` call. In order for the rename to

compiler/rustc_lint/src/builtin.rs

@@ -3181,7 +3181,7 @@ impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
         } = expr
         {
             for (template_sym, template_snippet, template_span) in template_strs.iter() {
-                let template_str = &template_sym.as_str();
+                let template_str = template_sym.as_str();
                 let find_label_span = |needle: &str| -> Option<Span> {
                     if let Some(template_snippet) = template_snippet {
                         let snippet = template_snippet.as_str();

compiler/rustc_lint/src/context.rs

@@ -381,10 +381,10 @@ impl LintStore {
             lint_name,
             self.lint_groups.keys().collect::<Vec<_>>()
         );
-        let lint_name_str = &*lint_name.as_str();
+        let lint_name_str = lint_name.as_str();
-        self.lint_groups.contains_key(&lint_name_str) || {
+        self.lint_groups.contains_key(lint_name_str) || {
             let warnings_name_str = crate::WARNINGS.name_lower();
-            lint_name_str == &*warnings_name_str
+            lint_name_str == warnings_name_str
         }
     }
 

compiler/rustc_lint/src/hidden_unicode_codepoints.rs

@@ -127,7 +127,7 @@ impl HiddenUnicodeCodepoints {
 impl EarlyLintPass for HiddenUnicodeCodepoints {
     fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
         if let ast::AttrKind::DocComment(_, comment) = attr.kind {
-            if contains_text_flow_control_chars(&comment.as_str()) {
+            if contains_text_flow_control_chars(comment.as_str()) {
                 self.lint_text_direction_codepoint(cx, comment, attr.span, 0, false, "doc comment");
             }
         }
@@ -138,7 +138,7 @@ impl EarlyLintPass for HiddenUnicodeCodepoints {
         let (text, span, padding) = match &expr.kind {
             ast::ExprKind::Lit(ast::Lit { token, kind, span }) => {
                 let text = token.symbol;
-                if !contains_text_flow_control_chars(&text.as_str()) {
+                if !contains_text_flow_control_chars(text.as_str()) {
                     return;
                 }
                 let padding = match kind {

compiler/rustc_lint/src/levels.rs

@@ -154,7 +154,7 @@ impl<'s> LintLevelsBuilder<'s> {
                         LintLevelSource::Node(_, forbid_source_span, reason) => {
                             diag_builder.span_label(forbid_source_span, "`forbid` level set here");
                             if let Some(rationale) = reason {
-                                diag_builder.note(&rationale.as_str());
+                                diag_builder.note(rationale.as_str());
                             }
                         }
                         LintLevelSource::CommandLine(_, _) => {

compiler/rustc_lint/src/non_ascii_idents.rs

@@ -218,8 +218,7 @@ impl EarlyLintPass for NonAsciiIdents {
                             cx.struct_span_lint(CONFUSABLE_IDENTS, sp, |lint| {
                                 lint.build(&format!(
                                     "identifier pair considered confusable between `{}` and `{}`",
-                                    existing_symbol.as_str(),
+                                    existing_symbol, symbol
-                                    symbol.as_str()
                                 ))
                                 .span_label(
                                     *existing_span,

compiler/rustc_lint/src/non_fmt_panic.rs

@@ -9,7 +9,7 @@ use rustc_middle::ty::subst::InternalSubsts;
 use rustc_parse_format::{ParseMode, Parser, Piece};
 use rustc_session::lint::FutureIncompatibilityReason;
 use rustc_span::edition::Edition;
-use rustc_span::{hygiene, sym, symbol::kw, symbol::SymbolStr, InnerSpan, Span, Symbol};
+use rustc_span::{hygiene, sym, symbol::kw, InnerSpan, Span, Symbol};
 use rustc_trait_selection::infer::InferCtxtExt;
 
 declare_lint! {
@@ -71,14 +71,14 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
     if let hir::ExprKind::Lit(lit) = &arg.kind {
         if let ast::LitKind::Str(sym, _) = lit.node {
             // The argument is a string literal.
-            check_panic_str(cx, f, arg, &sym.as_str());
+            check_panic_str(cx, f, arg, sym.as_str());
             return;
         }
     }
 
     // The argument is *not* a string literal.
 
-    let (span, panic, symbol_str) = panic_call(cx, f);
+    let (span, panic, symbol) = panic_call(cx, f);
 
     if in_external_macro(cx.sess(), span) {
         // Nothing that can be done about it in the current crate.
@@ -103,7 +103,7 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
 
     cx.struct_span_lint(NON_FMT_PANICS, arg_span, |lint| {
         let mut l = lint.build("panic message is not a string literal");
-        l.note(&format!("this usage of {}!() is deprecated; it will be a hard error in Rust 2021", symbol_str));
+        l.note(&format!("this usage of {}!() is deprecated; it will be a hard error in Rust 2021", symbol));
         l.note("for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/panic-macro-consistency.html>");
         if !is_arg_inside_call(arg_span, span) {
             // No clue where this argument is coming from.
@@ -112,7 +112,7 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
         }
         if arg_macro.map_or(false, |id| cx.tcx.is_diagnostic_item(sym::format_macro, id)) {
             // A case of `panic!(format!(..))`.
-            l.note(format!("the {}!() macro supports formatting, so there's no need for the format!() macro here", symbol_str).as_str());
+            l.note(format!("the {}!() macro supports formatting, so there's no need for the format!() macro here", symbol).as_str());
             if let Some((open, close, _)) = find_delimiters(cx, arg_span) {
                 l.multipart_suggestion(
                     "remove the `format!(..)` macro call",
@@ -301,7 +301,7 @@ fn find_delimiters<'tcx>(cx: &LateContext<'tcx>, span: Span) -> Option<(Span, Sp
     ))
 }
 
-fn panic_call<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>) -> (Span, Symbol, SymbolStr) {
+fn panic_call<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>) -> (Span, Symbol, Symbol) {
     let mut expn = f.span.ctxt().outer_expn_data();
 
     let mut panic_macro = kw::Empty;
@@ -328,7 +328,7 @@ fn panic_call<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>) -> (Span,
 
     let macro_symbol =
         if let hygiene::ExpnKind::Macro(_, symbol) = expn.kind { symbol } else { sym::panic };
-    (expn.call_site, panic_macro, macro_symbol.as_str())
+    (expn.call_site, panic_macro, macro_symbol)
 }
 
 fn is_arg_inside_call(arg: Span, call: Span) -> bool {

compiler/rustc_lint/src/nonstandard_style.rs

@@ -133,7 +133,7 @@ fn to_camel_case(s: &str) -> String {
 
 impl NonCamelCaseTypes {
     fn check_case(&self, cx: &EarlyContext<'_>, sort: &str, ident: &Ident) {
-        let name = &ident.name.as_str();
+        let name = ident.name.as_str();
 
         if !is_camel_case(name) {
             cx.struct_span_lint(NON_CAMEL_CASE_TYPES, ident.span, |lint| {
@@ -276,7 +276,7 @@ impl NonSnakeCase {
             })
         }
 
-        let name = &ident.name.as_str();
+        let name = ident.name.as_str();
 
         if !is_snake_case(name) {
             cx.struct_span_lint(NON_SNAKE_CASE, ident.span, |lint| {
@@ -484,7 +484,7 @@ declare_lint_pass!(NonUpperCaseGlobals => [NON_UPPER_CASE_GLOBALS]);
 
 impl NonUpperCaseGlobals {
     fn check_upper_case(cx: &LateContext<'_>, sort: &str, ident: &Ident) {
-        let name = &ident.name.as_str();
+        let name = ident.name.as_str();
         if name.chars().any(|c| c.is_lowercase()) {
             cx.struct_span_lint(NON_UPPER_CASE_GLOBALS, ident.span, |lint| {
                 let uc = NonSnakeCase::to_snake_case(&name).to_uppercase();

compiler/rustc_lint/src/unused.rs

@@ -315,7 +315,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
                         let mut err = lint.build(&msg);
                         // check for #[must_use = "..."]
                         if let Some(note) = attr.value_str() {
-                            err.note(&note.as_str());
+                            err.note(note.as_str());
                         }
                         err.emit();
                     });

compiler/rustc_metadata/src/creader.rs

@@ -292,7 +292,7 @@ impl<'a> CrateLoader<'a> {
             // `source` stores paths which are normalized which may be different
             // from the strings on the command line.
             let source = self.cstore.get_crate_data(cnum).cdata.source();
-            if let Some(entry) = self.sess.opts.externs.get(&name.as_str()) {
+            if let Some(entry) = self.sess.opts.externs.get(name.as_str()) {
                 // Only use `--extern crate_name=path` here, not `--extern crate_name`.
                 if let Some(mut files) = entry.files() {
                     if files.any(|l| {
@@ -381,7 +381,7 @@ impl<'a> CrateLoader<'a> {
         let host_hash = host_lib.as_ref().map(|lib| lib.metadata.get_root().hash());
 
         let private_dep =
-            self.sess.opts.externs.get(&name.as_str()).map_or(false, |e| e.is_private_dep);
+            self.sess.opts.externs.get(name.as_str()).map_or(false, |e| e.is_private_dep);
 
         // Claim this crate number and cache it
         let cnum = self.cstore.alloc_new_crate_num();
@@ -997,7 +997,7 @@ impl<'a> CrateLoader<'a> {
                 );
                 let name = match orig_name {
                     Some(orig_name) => {
-                        validate_crate_name(self.sess, &orig_name.as_str(), Some(item.span));
+                        validate_crate_name(self.sess, orig_name.as_str(), Some(item.span));
                         orig_name
                     }
                     None => item.ident.name,

compiler/rustc_metadata/src/locator.rs

@@ -315,7 +315,7 @@ impl<'a> CrateLocator<'a> {
             exact_paths: if hash.is_none() {
                 sess.opts
                     .externs
-                    .get(&crate_name.as_str())
+                    .get(crate_name.as_str())
                     .into_iter()
                     .filter_map(|entry| entry.files())
                     .flatten()
@@ -976,7 +976,8 @@ impl CrateError {
                 let candidates = libraries
                     .iter()
                     .map(|lib| {
-                        let crate_name = &lib.metadata.get_root().name().as_str();
+                        let crate_name = lib.metadata.get_root().name();
+                        let crate_name = crate_name.as_str();
                         let mut paths = lib.source.paths();
 
                         // This `unwrap()` should be okay because there has to be at least one
@@ -1174,7 +1175,7 @@ impl CrateError {
                     } else if crate_name
                         == Symbol::intern(&sess.opts.debugging_opts.profiler_runtime)
                     {
-                        err.note(&"the compiler may have been built without the profiler runtime");
+                        err.note("the compiler may have been built without the profiler runtime");
                     } else if crate_name.as_str().starts_with("rustc_") {
                         err.help(
                             "maybe you need to install the missing components with: \

compiler/rustc_metadata/src/native_libs.rs

@@ -67,7 +67,7 @@ impl<'tcx> ItemLikeVisitor<'tcx> for Collector<'tcx> {
                         Some(name) => name,
                         None => continue, // skip like historical compilers
                     };
-                    lib.kind = match &*kind.as_str() {
+                    lib.kind = match kind.as_str() {
                         "static" => NativeLibKind::Static { bundle: None, whole_archive: None },
                         "static-nobundle" => {
                             sess.struct_span_warn(

compiler/rustc_middle/src/lint.rs

@@ -319,7 +319,7 @@ pub fn struct_lint_level<'s, 'd>(
             }
             LintLevelSource::Node(lint_attr_name, src, reason) => {
                 if let Some(rationale) = reason {
-                    err.note(&rationale.as_str());
+                    err.note(rationale.as_str());
                 }
                 sess.diag_span_note_once(
                     &mut err,

compiler/rustc_middle/src/middle/mod.rs

@@ -21,7 +21,7 @@ pub mod lib_features {
                 .map(|(f, s)| (*f, Some(*s)))
                 .chain(self.unstable.iter().map(|f| (*f, None)))
                 .collect();
-            all_features.sort_unstable_by_key(|f| f.0.as_str());
+            all_features.sort_unstable_by(|a, b| a.0.as_str().partial_cmp(b.0.as_str()).unwrap());
             all_features
         }
     }

compiler/rustc_middle/src/middle/stability.rs

@@ -131,8 +131,7 @@ pub fn report_unstable(
 /// deprecated (i.e., whether X is not greater than the current rustc version).
 pub fn deprecation_in_effect(depr: &Deprecation) -> bool {
     let is_since_rustc_version = depr.is_since_rustc_version;
-    let since = depr.since.map(Symbol::as_str);
+    let since = depr.since.as_ref().map(Symbol::as_str);
-    let since = since.as_deref();
 
     fn parse_version(ver: &str) -> Vec<u32> {
         // We ignore non-integer components of the version (e.g., "nightly").
@@ -197,7 +196,7 @@ fn deprecation_message(
     let message = if is_in_effect {
         format!("use of deprecated {} `{}`", kind, path)
     } else {
-        let since = since.map(Symbol::as_str);
+        let since = since.as_ref().map(Symbol::as_str);
 
         if since.as_deref() == Some("TBD") {
             format!("use of {} `{}` that will be deprecated in a future Rust version", kind, path)

compiler/rustc_middle/src/mir/mod.rs

@@ -2444,7 +2444,7 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                             CtorKind::Fictive => {
                                 let mut struct_fmt = fmt.debug_struct(&name);
                                 for (field, place) in iter::zip(&variant_def.fields, places) {
-                                    struct_fmt.field(&field.ident.as_str(), place);
+                                    struct_fmt.field(field.ident.as_str(), place);
                                 }
                                 struct_fmt.finish()
                             }
@@ -2473,7 +2473,7 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                             if let Some(upvars) = tcx.upvars_mentioned(def_id) {
                                 for (&var_id, place) in iter::zip(upvars.keys(), places) {
                                     let var_name = tcx.hir().name(var_id);
-                                    struct_fmt.field(&var_name.as_str(), place);
+                                    struct_fmt.field(var_name.as_str(), place);
                                 }
                             }
 
@@ -2493,7 +2493,7 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                             if let Some(upvars) = tcx.upvars_mentioned(def_id) {
                                 for (&var_id, place) in iter::zip(upvars.keys(), places) {
                                     let var_name = tcx.hir().name(var_id);
-                                    struct_fmt.field(&var_name.as_str(), place);
+                                    struct_fmt.field(var_name.as_str(), place);
                                 }
                             }
 

compiler/rustc_middle/src/mir/mono.rs

@@ -338,7 +338,7 @@ impl<'tcx> CodegenUnit<'tcx> {
     }
 
     pub fn work_product_id(&self) -> WorkProductId {
-        WorkProductId::from_cgu_name(&self.name().as_str())
+        WorkProductId::from_cgu_name(self.name().as_str())
     }
 
     pub fn work_product(&self, tcx: TyCtxt<'_>) -> WorkProduct {
@@ -470,7 +470,7 @@ impl CodegenUnitNameBuilder<'tcx> {
         if self.tcx.sess.opts.debugging_opts.human_readable_cgu_names {
             cgu_name
         } else {
-            Symbol::intern(&CodegenUnit::mangle_name(&cgu_name.as_str()))
+            Symbol::intern(&CodegenUnit::mangle_name(cgu_name.as_str()))
         }
     }
 

compiler/rustc_middle/src/ty/context.rs

@@ -1216,8 +1216,8 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     pub fn consider_optimizing<T: Fn() -> String>(self, msg: T) -> bool {
-        let cname = self.crate_name(LOCAL_CRATE).as_str();
+        let cname = self.crate_name(LOCAL_CRATE);
-        self.sess.consider_optimizing(&cname, msg)
+        self.sess.consider_optimizing(cname.as_str(), msg)
     }
 
     /// Obtain all lang items of this crate and all dependencies (recursively)

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -303,7 +303,7 @@ pub trait PrettyPrinter<'tcx>:
         match self.tcx().trimmed_def_paths(()).get(&def_id) {
             None => Ok((self, false)),
             Some(symbol) => {
-                self.write_str(&symbol.as_str())?;
+                self.write_str(symbol.as_str())?;
                 Ok((self, true))
             }
         }

compiler/rustc_monomorphize/src/partitioning/merging.rs

@@ -3,7 +3,7 @@ use std::cmp;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::mir::mono::{CodegenUnit, CodegenUnitNameBuilder};
-use rustc_span::symbol::{Symbol, SymbolStr};
+use rustc_span::symbol::Symbol;
 
 use super::PartitioningCx;
 use crate::partitioning::PreInliningPartitioning;
@@ -24,11 +24,11 @@ pub fn merge_codegen_units<'tcx>(
     // smallest into each other) we're sure to start off with a deterministic
     // order (sorted by name). This'll mean that if two cgus have the same size
     // the stable sort below will keep everything nice and deterministic.
-    codegen_units.sort_by_cached_key(|cgu| cgu.name().as_str());
+    codegen_units.sort_by(|a, b| a.name().as_str().partial_cmp(b.name().as_str()).unwrap());
 
     // This map keeps track of what got merged into what.
-    let mut cgu_contents: FxHashMap<Symbol, Vec<SymbolStr>> =
+    let mut cgu_contents: FxHashMap<Symbol, Vec<Symbol>> =
-        codegen_units.iter().map(|cgu| (cgu.name(), vec![cgu.name().as_str()])).collect();
+        codegen_units.iter().map(|cgu| (cgu.name(), vec![cgu.name()])).collect();
 
     // Merge the two smallest codegen units until the target size is reached.
     while codegen_units.len() > cx.target_cgu_count {
@@ -69,7 +69,7 @@ pub fn merge_codegen_units<'tcx>(
             // were actually modified by merging.
             .filter(|(_, cgu_contents)| cgu_contents.len() > 1)
             .map(|(current_cgu_name, cgu_contents)| {
-                let mut cgu_contents: Vec<&str> = cgu_contents.iter().map(|s| &s[..]).collect();
+                let mut cgu_contents: Vec<&str> = cgu_contents.iter().map(|s| s.as_str()).collect();
 
                 // Sort the names, so things are deterministic and easy to
                 // predict.

compiler/rustc_monomorphize/src/partitioning/mod.rs

@@ -208,7 +208,7 @@ pub fn partition<'tcx>(
         internalization_candidates: _,
     } = post_inlining;
 
-    result.sort_by_cached_key(|cgu| cgu.name().as_str());
+    result.sort_by(|a, b| a.name().as_str().partial_cmp(b.name().as_str()).unwrap());
 
     result
 }
@@ -366,7 +366,7 @@ fn collect_and_partition_mono_items<'tcx>(
         for cgu in codegen_units {
             tcx.prof.artifact_size(
                 "codegen_unit_size_estimate",
-                &cgu.name().as_str()[..],
+                cgu.name().as_str(),
                 cgu.size_estimate() as u64,
             );
         }
@@ -401,7 +401,7 @@ fn collect_and_partition_mono_items<'tcx>(
                 cgus.dedup();
                 for &(ref cgu_name, (linkage, _)) in cgus.iter() {
                     output.push(' ');
-                    output.push_str(&cgu_name.as_str());
+                    output.push_str(cgu_name.as_str());
 
                     let linkage_abbrev = match linkage {
                         Linkage::External => "External",

compiler/rustc_parse/src/parser/expr.rs

@@ -1639,7 +1639,7 @@ impl<'a> Parser<'a> {
                     next_token.kind
                 {
                     if self.token.span.hi() == next_token.span.lo() {
-                        let s = String::from("0.") + &symbol.as_str();
+                        let s = String::from("0.") + symbol.as_str();
                         let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
                         return Some(Token::new(kind, self.token.span.to(next_token.span)));
                     }
@@ -1710,7 +1710,8 @@ impl<'a> Parser<'a> {
                 );
             }
             LitError::InvalidIntSuffix => {
-                let suf = suffix.expect("suffix error with no suffix").as_str();
+                let suf = suffix.expect("suffix error with no suffix");
+                let suf = suf.as_str();
                 if looks_like_width_suffix(&['i', 'u'], &suf) {
                     // If it looks like a width, try to be helpful.
                     let msg = format!("invalid width `{}` for integer literal", &suf[1..]);
@@ -1726,8 +1727,9 @@ impl<'a> Parser<'a> {
                 }
             }
             LitError::InvalidFloatSuffix => {
-                let suf = suffix.expect("suffix error with no suffix").as_str();
+                let suf = suffix.expect("suffix error with no suffix");
-                if looks_like_width_suffix(&['f'], &suf) {
+                let suf = suf.as_str();
+                if looks_like_width_suffix(&['f'], suf) {
                     // If it looks like a width, try to be helpful.
                     let msg = format!("invalid width `{}` for float literal", &suf[1..]);
                     self.struct_span_err(span, &msg).help("valid widths are 32 and 64").emit();

compiler/rustc_passes/src/check_attr.rs

@@ -607,7 +607,7 @@ impl CheckAttrVisitor<'_> {
             return err_fn(meta.span(), &format!("isn't allowed on {}", err));
         }
         let item_name = self.tcx.hir().name(hir_id);
-        if &*item_name.as_str() == doc_alias {
+        if item_name.as_str() == doc_alias {
             return err_fn(meta.span(), "is the same as the item's name");
         }
         let span = meta.span();
@@ -636,7 +636,7 @@ impl CheckAttrVisitor<'_> {
                         LitKind::Str(s, _) => {
                             if !self.check_doc_alias_value(
                                 v,
-                                &s.as_str(),
+                                s.as_str(),
                                 hir_id,
                                 target,
                                 true,

compiler/rustc_passes/src/liveness.rs

@@ -1464,7 +1464,7 @@ impl<'tcx> Liveness<'_, 'tcx> {
         if name == kw::Empty {
             return None;
         }
-        let name: &str = &name.as_str();
+        let name = name.as_str();
         if name.as_bytes()[0] == b'_' {
             return None;
         }

compiler/rustc_query_impl/src/profiling_support.rs

@@ -61,8 +61,8 @@ impl<'p, 'c, 'tcx> QueryKeyStringBuilder<'p, 'c, 'tcx> {
 
         match def_key.disambiguated_data.data {
             DefPathData::CrateRoot => {
-                crate_name = self.tcx.crate_name(def_id.krate).as_str();
+                crate_name = self.tcx.crate_name(def_id.krate);
-                name = &*crate_name;
+                name = crate_name.as_str();
                 dis = "";
                 end_index = 3;
             }

compiler/rustc_resolve/src/diagnostics.rs

@@ -1,4 +1,3 @@
-use std::cmp::Reverse;
 use std::ptr;
 
 use rustc_ast::{self as ast, Path};
@@ -784,7 +783,7 @@ impl<'a> Resolver<'a> {
         });
 
         // Make sure error reporting is deterministic.
-        suggestions.sort_by_cached_key(|suggestion| suggestion.candidate.as_str());
+        suggestions.sort_by(|a, b| a.candidate.as_str().partial_cmp(b.candidate.as_str()).unwrap());
 
         match find_best_match_for_name(
             &suggestions.iter().map(|suggestion| suggestion.candidate).collect::<Vec<Symbol>>(),
@@ -1186,7 +1185,7 @@ impl<'a> Resolver<'a> {
                 ("", " from prelude")
             } else if b.is_extern_crate()
                 && !b.is_import()
-                && self.session.opts.externs.get(&ident.as_str()).is_some()
+                && self.session.opts.externs.get(ident.as_str()).is_some()
             {
                 ("", " passed with `--extern`")
             } else if add_built_in {
@@ -1481,12 +1480,12 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
             return None;
         }
 
-        // Sort extern crate names in reverse order to get
+        // Sort extern crate names in *reverse* order to get
         // 1) some consistent ordering for emitted diagnostics, and
         // 2) `std` suggestions before `core` suggestions.
         let mut extern_crate_names =
             self.r.extern_prelude.iter().map(|(ident, _)| ident.name).collect::<Vec<_>>();
-        extern_crate_names.sort_by_key(|name| Reverse(name.as_str()));
+        extern_crate_names.sort_by(|a, b| b.as_str().partial_cmp(a.as_str()).unwrap());
 
         for name in extern_crate_names.into_iter() {
             // Replace first ident with a crate name and check if that is valid.

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -231,7 +231,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
 
         let is_assoc_fn = self.self_type_is_available(span);
         // Emit help message for fake-self from other languages (e.g., `this` in Javascript).
-        if ["this", "my"].contains(&&*item_str.as_str()) && is_assoc_fn {
+        if ["this", "my"].contains(&item_str.as_str()) && is_assoc_fn {
             err.span_suggestion_short(
                 span,
                 "you might have meant to use `self` here instead",
@@ -1358,7 +1358,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
 
         let name = path[path.len() - 1].ident.name;
         // Make sure error reporting is deterministic.
-        names.sort_by_cached_key(|suggestion| suggestion.candidate.as_str());
+        names.sort_by(|a, b| a.candidate.as_str().partial_cmp(b.candidate.as_str()).unwrap());
 
         match find_best_match_for_name(
             &names.iter().map(|suggestion| suggestion.candidate).collect::<Vec<Symbol>>(),
@@ -1377,7 +1377,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
     fn likely_rust_type(path: &[Segment]) -> Option<Symbol> {
         let name = path[path.len() - 1].ident.as_str();
         // Common Java types
-        Some(match &*name {
+        Some(match name {
             "byte" => sym::u8, // In Java, bytes are signed, but in practice one almost always wants unsigned bytes.
             "short" => sym::i16,
             "boolean" => sym::bool,
@@ -2345,7 +2345,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                         _ => None,
                     });
                 }
-                suggest_existing(err, &name.as_str()[..], suggs);
+                suggest_existing(err, name.as_str(), suggs);
             }
             [] => {
                 let mut suggs = Vec::new();

compiler/rustc_resolve/src/late/lifetimes.rs

@@ -689,11 +689,11 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
         hir_id: hir::HirId,
     ) {
         let name = match fk {
-            intravisit::FnKind::ItemFn(id, _, _, _) => id.as_str(),
+            intravisit::FnKind::ItemFn(id, _, _, _) => id.name,
-            intravisit::FnKind::Method(id, _, _) => id.as_str(),
+            intravisit::FnKind::Method(id, _, _) => id.name,
-            intravisit::FnKind::Closure => Symbol::intern("closure").as_str(),
+            intravisit::FnKind::Closure => sym::closure,
         };
-        let name: &str = &name;
+        let name = name.as_str();
         let span = span!(Level::DEBUG, "visit_fn", name);
         let _enter = span.enter();
         match fk {

compiler/rustc_resolve/src/lib.rs

@@ -3481,7 +3481,7 @@ fn names_to_string(names: &[Symbol]) -> String {
         if Ident::with_dummy_span(*name).is_raw_guess() {
             result.push_str("r#");
         }
-        result.push_str(&name.as_str());
+        result.push_str(name.as_str());
     }
     result
 }

compiler/rustc_resolve/src/macros.rs

@@ -105,7 +105,7 @@ fn fast_print_path(path: &ast::Path) -> Symbol {
                 path_str.push_str("::");
             }
             if segment.ident.name != kw::PathRoot {
-                path_str.push_str(&segment.ident.as_str())
+                path_str.push_str(segment.ident.as_str())
             }
         }
         Symbol::intern(&path_str)

compiler/rustc_save_analysis/src/lib.rs

@@ -825,7 +825,7 @@ impl<'tcx> SaveContext<'tcx> {
         for attr in attrs {
             if let Some(val) = attr.doc_str() {
                 // FIXME: Should save-analysis beautify doc strings itself or leave it to users?
-                result.push_str(&beautify_doc_string(val).as_str());
+                result.push_str(beautify_doc_string(val).as_str());
                 result.push('\n');
             }
         }

compiler/rustc_save_analysis/src/sig.rs

@@ -616,7 +616,7 @@ impl<'hir> Sig for hir::Generics<'hir> {
             if let hir::GenericParamKind::Const { .. } = param.kind {
                 param_text.push_str("const ");
             }
-            param_text.push_str(&param.name.ident().as_str());
+            param_text.push_str(param.name.ident().as_str());
             defs.push(SigElement {
                 id: id_from_hir_id(param.hir_id, scx),
                 start: offset + text.len(),

compiler/rustc_session/src/output.rs

@@ -60,7 +60,7 @@ pub fn find_crate_name(sess: &Session, attrs: &[ast::Attribute], input: &Input)
 
     if let Some(ref s) = sess.opts.crate_name {
         if let Some((attr, name)) = attr_crate_name {
-            if name.as_str() != *s {
+            if name.as_str() != s {
                 let msg = format!(
                     "`--crate-name` and `#[crate_name]` are \
                                    required to match, but `{}` != `{}`",

compiler/rustc_span/src/lev_distance.rs

@@ -55,7 +55,7 @@ pub fn find_best_match_for_name(
     lookup: Symbol,
     dist: Option<usize>,
 ) -> Option<Symbol> {
-    let lookup = &lookup.as_str();
+    let lookup = lookup.as_str();
     let max_dist = dist.unwrap_or_else(|| cmp::max(lookup.len(), 3) / 3);
 
     // Priority of matches:
@@ -70,7 +70,7 @@ pub fn find_best_match_for_name(
     let levenshtein_match = name_vec
         .iter()
         .filter_map(|&name| {
-            let dist = lev_distance(lookup, &name.as_str());
+            let dist = lev_distance(lookup, name.as_str());
             if dist <= max_dist { Some((name, dist)) } else { None }
         })
         // Here we are collecting the next structure:
@@ -88,7 +88,7 @@ pub fn find_best_match_for_name(
 
 fn find_match_by_sorted_words(iter_names: &[Symbol], lookup: &str) -> Option<Symbol> {
     iter_names.iter().fold(None, |result, candidate| {
-        if sort_by_words(&candidate.as_str()) == sort_by_words(lookup) {
+        if sort_by_words(candidate.as_str()) == sort_by_words(lookup) {
             Some(*candidate)
         } else {
             result

compiler/rustc_span/src/symbol.rs

@@ -1512,9 +1512,12 @@ impl Ident {
         Ident::new(self.name, self.span.normalize_to_macro_rules())
     }
 
-    /// Convert the name to a `SymbolStr`. This is a slowish operation because
+    /// Access the underlying string. This is a slowish operation because it
-    /// it requires locking the symbol interner.
+    /// requires locking the symbol interner.
-    pub fn as_str(self) -> SymbolStr {
+    ///
+    /// Note that the lifetime of the return value is a lie. See
+    /// `Symbol::as_str()` for details.
+    pub fn as_str(&self) -> &str {
         self.name.as_str()
     }
 }
@@ -1650,12 +1653,17 @@ impl Symbol {
         with_session_globals(|session_globals| session_globals.symbol_interner.intern(string))
     }
 
-    /// Convert to a `SymbolStr`. This is a slowish operation because it
+    /// Access the underlying string. This is a slowish operation because it
     /// requires locking the symbol interner.
-    pub fn as_str(self) -> SymbolStr {
+    ///
-        with_session_globals(|session_globals| {
+    /// Note that the lifetime of the return value is a lie. It's not the same
-            let symbol_str = session_globals.symbol_interner.get(self);
+    /// as `&self`, but actually tied to the lifetime of the underlying
-            unsafe { SymbolStr { string: std::mem::transmute::<&str, &str>(symbol_str) } }
+    /// interner. Interners are long-lived, and there are very few of them, and
+    /// this function is typically used for short-lived things, so in practice
+    /// it works out ok.
+    pub fn as_str(&self) -> &str {
+        with_session_globals(|session_globals| unsafe {
+            std::mem::transmute::<&str, &str>(session_globals.symbol_interner.get(*self))
         })
     }
 
@@ -1678,19 +1686,19 @@ impl Symbol {
 
 impl fmt::Debug for Symbol {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Debug::fmt(&self.as_str(), f)
+        fmt::Debug::fmt(self.as_str(), f)
     }
 }
 
 impl fmt::Display for Symbol {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(&self.as_str(), f)
+        fmt::Display::fmt(self.as_str(), f)
     }
 }
 
 impl<S: Encoder> Encodable<S> for Symbol {
     fn encode(&self, s: &mut S) -> Result<(), S::Error> {
-        s.emit_str(&self.as_str())
+        s.emit_str(self.as_str())
     }
 }
 
@@ -1709,11 +1717,10 @@ impl<CTX> HashStable<CTX> for Symbol {
 }
 
 impl<CTX> ToStableHashKey<CTX> for Symbol {
-    type KeyType = SymbolStr;
+    type KeyType = String;
-
     #[inline]
-    fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
+    fn to_stable_hash_key(&self, _: &CTX) -> String {
-        self.as_str()
+        self.as_str().to_string()
     }
 }
 
@@ -1905,70 +1912,3 @@ impl Ident {
         self.name.can_be_raw() && self.is_reserved()
     }
 }
-
-/// An alternative to [`Symbol`], useful when the chars within the symbol need to
-/// be accessed. It deliberately has limited functionality and should only be
-/// used for temporary values.
-///
-/// Because the interner outlives any thread which uses this type, we can
-/// safely treat `string` which points to interner data, as an immortal string,
-/// as long as this type never crosses between threads.
-//
-// FIXME: ensure that the interner outlives any thread which uses `SymbolStr`,
-// by creating a new thread right after constructing the interner.
-#[derive(Clone, Eq, PartialOrd, Ord)]
-pub struct SymbolStr {
-    string: &'static str,
-}
-
-// This impl allows a `SymbolStr` to be directly equated with a `String` or
-// `&str`.
-impl<T: std::ops::Deref<Target = str>> std::cmp::PartialEq<T> for SymbolStr {
-    fn eq(&self, other: &T) -> bool {
-        self.string == other.deref()
-    }
-}
-
-impl !Send for SymbolStr {}
-impl !Sync for SymbolStr {}
-
-/// This impl means that if `ss` is a `SymbolStr`:
-/// - `*ss` is a `str`;
-/// - `&*ss` is a `&str` (and `match &*ss { ... }` is a common pattern).
-/// - `&ss as &str` is a `&str`, which means that `&ss` can be passed to a
-///   function expecting a `&str`.
-impl std::ops::Deref for SymbolStr {
-    type Target = str;
-    #[inline]
-    fn deref(&self) -> &str {
-        self.string
-    }
-}
-
-impl fmt::Debug for SymbolStr {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Debug::fmt(self.string, f)
-    }
-}
-
-impl fmt::Display for SymbolStr {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(self.string, f)
-    }
-}
-
-impl<CTX> HashStable<CTX> for SymbolStr {
-    #[inline]
-    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
-        self.string.hash_stable(hcx, hasher)
-    }
-}
-
-impl<CTX> ToStableHashKey<CTX> for SymbolStr {
-    type KeyType = SymbolStr;
-
-    #[inline]
-    fn to_stable_hash_key(&self, _: &CTX) -> SymbolStr {
-        self.clone()
-    }
-}

compiler/rustc_symbol_mangling/src/legacy.rs

@@ -255,7 +255,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolPrinter<'tcx> {
     }
 
     fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
-        self.write_str(&self.tcx.crate_name(cnum).as_str())?;
+        self.write_str(self.tcx.crate_name(cnum).as_str())?;
         Ok(self)
     }
     fn path_qualified(

compiler/rustc_symbol_mangling/src/v0.rs

@@ -9,6 +9,7 @@ use rustc_middle::ty::layout::IntegerExt;
 use rustc_middle::ty::print::{Print, Printer};
 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, Subst};
 use rustc_middle::ty::{self, FloatTy, Instance, IntTy, Ty, TyCtxt, TypeFoldable, UintTy};
+use rustc_span::symbol::kw;
 use rustc_target::abi::call::FnAbi;
 use rustc_target::abi::Integer;
 use rustc_target::spec::abi::Abi;
@@ -559,7 +560,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
                     ty::ExistentialPredicate::Projection(projection) => {
                         let name = cx.tcx.associated_item(projection.item_def_id).ident;
                         cx.push("p");
-                        cx.push_ident(&name.as_str());
+                        cx.push_ident(name.as_str());
                         cx = projection.ty.print(cx)?;
                     }
                     ty::ExistentialPredicate::AutoTrait(def_id) => {
@@ -702,12 +703,11 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
                                     // just to be able to handle disambiguators.
                                     let disambiguated_field =
                                         self.tcx.def_key(field_def.did).disambiguated_data;
-                                    let field_name =
+                                    let field_name = disambiguated_field.data.get_opt_name();
-                                        disambiguated_field.data.get_opt_name().map(|s| s.as_str());
                                     self.push_disambiguator(
                                         disambiguated_field.disambiguator as u64,
                                     );
-                                    self.push_ident(&field_name.as_ref().map_or("", |s| &s[..]));
+                                    self.push_ident(field_name.unwrap_or(kw::Empty).as_str());
 
                                     self = field.print(self)?;
                                 }
@@ -736,8 +736,8 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
         self.push("C");
         let stable_crate_id = self.tcx.def_path_hash(cnum.as_def_id()).stable_crate_id();
         self.push_disambiguator(stable_crate_id.to_u64());
-        let name = self.tcx.crate_name(cnum).as_str();
+        let name = self.tcx.crate_name(cnum);
-        self.push_ident(&name);
+        self.push_ident(name.as_str());
         Ok(self)
     }
 
@@ -793,13 +793,13 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
             }
         };
 
-        let name = disambiguated_data.data.get_opt_name().map(|s| s.as_str());
+        let name = disambiguated_data.data.get_opt_name();
 
         self.path_append_ns(
             print_prefix,
             ns,
             disambiguated_data.disambiguator as u64,
-            name.as_ref().map_or("", |s| &s[..]),
+            name.unwrap_or(kw::Empty).as_str(),
         )
     }
 

compiler/rustc_target/src/asm/mod.rs

@@ -298,43 +298,43 @@ impl InlineAsmReg {
         let name = name.as_str();
         Ok(match arch {
             InlineAsmArch::X86 | InlineAsmArch::X86_64 => {
-                Self::X86(X86InlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::X86(X86InlineAsmReg::parse(arch, has_feature, target, name)?)
             }
             InlineAsmArch::Arm => {
-                Self::Arm(ArmInlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::Arm(ArmInlineAsmReg::parse(arch, has_feature, target, name)?)
             }
             InlineAsmArch::AArch64 => {
-                Self::AArch64(AArch64InlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::AArch64(AArch64InlineAsmReg::parse(arch, has_feature, target, name)?)
             }
             InlineAsmArch::RiscV32 | InlineAsmArch::RiscV64 => {
-                Self::RiscV(RiscVInlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::RiscV(RiscVInlineAsmReg::parse(arch, has_feature, target, name)?)
             }
             InlineAsmArch::Nvptx64 => {
-                Self::Nvptx(NvptxInlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::Nvptx(NvptxInlineAsmReg::parse(arch, has_feature, target, name)?)
             }
             InlineAsmArch::PowerPC | InlineAsmArch::PowerPC64 => {
-                Self::PowerPC(PowerPCInlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::PowerPC(PowerPCInlineAsmReg::parse(arch, has_feature, target, name)?)
             }
             InlineAsmArch::Hexagon => {
-                Self::Hexagon(HexagonInlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::Hexagon(HexagonInlineAsmReg::parse(arch, has_feature, target, name)?)
             }
             InlineAsmArch::Mips | InlineAsmArch::Mips64 => {
-                Self::Mips(MipsInlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::Mips(MipsInlineAsmReg::parse(arch, has_feature, target, name)?)
             }
             InlineAsmArch::S390x => {
-                Self::S390x(S390xInlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::S390x(S390xInlineAsmReg::parse(arch, has_feature, target, name)?)
             }
             InlineAsmArch::SpirV => {
-                Self::SpirV(SpirVInlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::SpirV(SpirVInlineAsmReg::parse(arch, has_feature, target, name)?)
             }
             InlineAsmArch::Wasm32 | InlineAsmArch::Wasm64 => {
-                Self::Wasm(WasmInlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::Wasm(WasmInlineAsmReg::parse(arch, has_feature, target, name)?)
             }
             InlineAsmArch::Bpf => {
-                Self::Bpf(BpfInlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::Bpf(BpfInlineAsmReg::parse(arch, has_feature, target, name)?)
             }
             InlineAsmArch::Avr => {
-                Self::Avr(AvrInlineAsmReg::parse(arch, has_feature, target, &name)?)
+                Self::Avr(AvrInlineAsmReg::parse(arch, has_feature, target, name)?)
             }
         })
     }
@@ -798,7 +798,7 @@ impl InlineAsmClobberAbi {
         target: &Target,
         name: Symbol,
     ) -> Result<Self, &'static [&'static str]> {
-        let name = &*name.as_str();
+        let name = name.as_str();
         match arch {
             InlineAsmArch::X86 => match name {
                 "C" | "system" | "efiapi" | "cdecl" | "stdcall" | "fastcall" => {

compiler/rustc_trait_selection/src/traits/on_unimplemented.rs

@@ -269,7 +269,7 @@ impl<'tcx> OnUnimplementedFormatString {
         let name = tcx.item_name(trait_def_id);
         let generics = tcx.generics_of(trait_def_id);
         let s = self.0.as_str();
-        let parser = Parser::new(&s, None, None, false, ParseMode::Format);
+        let parser = Parser::new(s, None, None, false, ParseMode::Format);
         let mut result = Ok(());
         for token in parser {
             match token {
@@ -347,7 +347,7 @@ impl<'tcx> OnUnimplementedFormatString {
         let empty_string = String::new();
 
         let s = self.0.as_str();
-        let parser = Parser::new(&s, None, None, false, ParseMode::Format);
+        let parser = Parser::new(s, None, None, false, ParseMode::Format);
         let item_context = (options.get(&sym::ItemContext)).unwrap_or(&empty_string);
         parser
             .map(|p| match p {

compiler/rustc_typeck/src/check/generator_interior.rs

@@ -609,7 +609,7 @@ fn check_must_not_suspend_def(
                     // Add optional reason note
                     if let Some(note) = attr.value_str() {
                         // FIXME(guswynn): consider formatting this better
-                        err.span_note(data.source_span, &note.as_str());
+                        err.span_note(data.source_span, note.as_str());
                     }
 
                     // Add some quick suggestions on what to do

compiler/rustc_typeck/src/check/method/probe.rs

@@ -1038,7 +1038,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             .collect();
 
         // Sort them by the name so we have a stable result.
-        names.sort_by_cached_key(|n| n.as_str());
+        names.sort_by(|a, b| a.as_str().partial_cmp(b.as_str()).unwrap());
         names
     }
 
@@ -1908,7 +1908,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     .associated_items(def_id)
                     .in_definition_order()
                     .filter(|x| {
-                        let dist = lev_distance(&*name.as_str(), &x.ident.as_str());
+                        let dist = lev_distance(name.as_str(), x.ident.as_str());
                         x.kind.namespace() == Namespace::ValueNS && dist > 0 && dist <= max_dist
                     })
                     .copied()

compiler/rustc_typeck/src/collect.rs

@@ -2849,7 +2849,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
             );
         } else if attr.has_name(sym::linkage) {
             if let Some(val) = attr.value_str() {
-                codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
+                codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, val.as_str()));
             }
         } else if attr.has_name(sym::link_section) {
             if let Some(val) = attr.value_str() {

src/librustdoc/clean/cfg.rs

@@ -466,7 +466,7 @@ impl<'a> fmt::Display for Display<'a> {
                     (sym::unix, None) => "Unix",
                     (sym::windows, None) => "Windows",
                     (sym::debug_assertions, None) => "debug-assertions enabled",
-                    (sym::target_os, Some(os)) => match &*os.as_str() {
+                    (sym::target_os, Some(os)) => match os.as_str() {
                         "android" => "Android",
                         "dragonfly" => "DragonFly BSD",
                         "emscripten" => "Emscripten",
@@ -487,7 +487,7 @@ impl<'a> fmt::Display for Display<'a> {
                         "windows" => "Windows",
                         _ => "",
                     },
-                    (sym::target_arch, Some(arch)) => match &*arch.as_str() {
+                    (sym::target_arch, Some(arch)) => match arch.as_str() {
                         "aarch64" => "AArch64",
                         "arm" => "ARM",
                         "asmjs" => "JavaScript",
@@ -504,14 +504,14 @@ impl<'a> fmt::Display for Display<'a> {
                         "x86_64" => "x86-64",
                         _ => "",
                     },
-                    (sym::target_vendor, Some(vendor)) => match &*vendor.as_str() {
+                    (sym::target_vendor, Some(vendor)) => match vendor.as_str() {
                         "apple" => "Apple",
                         "pc" => "PC",
                         "sun" => "Sun",
                         "fortanix" => "Fortanix",
                         _ => "",
                     },
-                    (sym::target_env, Some(env)) => match &*env.as_str() {
+                    (sym::target_env, Some(env)) => match env.as_str() {
                         "gnu" => "GNU",
                         "msvc" => "MSVC",
                         "musl" => "musl",
@@ -545,14 +545,14 @@ impl<'a> fmt::Display for Display<'a> {
                         write!(
                             fmt,
                             r#"<code>{}="{}"</code>"#,
-                            Escape(&name.as_str()),
+                            Escape(name.as_str()),
-                            Escape(&v.as_str())
+                            Escape(v.as_str())
                         )
                     } else {
                         write!(fmt, r#"`{}="{}"`"#, name, v)
                     }
                 } else if self.1.is_html() {
-                    write!(fmt, "<code>{}</code>", Escape(&name.as_str()))
+                    write!(fmt, "<code>{}</code>", Escape(name.as_str()))
                 } else {
                     write!(fmt, "`{}`", name)
                 }

src/librustdoc/clean/types.rs

@@ -25,7 +25,7 @@ use rustc_middle::ty::{self, TyCtxt};
 use rustc_session::Session;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::source_map::DUMMY_SP;
-use rustc_span::symbol::{kw, sym, Ident, Symbol, SymbolStr};
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{self, FileName, Loc};
 use rustc_target::abi::VariantIdx;
 use rustc_target::spec::abi::Abi;
@@ -200,7 +200,7 @@ impl ExternalCrate {
         // See if there's documentation generated into the local directory
         // WARNING: since rustdoc creates these directories as it generates documentation, this check is only accurate before rendering starts.
         // Make sure to call `location()` by that time.
-        let local_location = dst.join(&*self.name(tcx).as_str());
+        let local_location = dst.join(self.name(tcx).as_str());
         if local_location.is_dir() {
             return Local;
         }
@@ -2009,10 +2009,6 @@ impl Path {
         self.segments.last().expect("segments were empty").name
     }
 
-    crate fn last_name(&self) -> SymbolStr {
-        self.segments.last().expect("segments were empty").name.as_str()
-    }
-
     crate fn whole_name(&self) -> String {
         self.segments
             .iter()

src/librustdoc/clean/utils.rs

@@ -162,7 +162,7 @@ crate fn qpath_to_string(p: &hir::QPath<'_>) -> String {
             s.push_str("::");
         }
         if seg.ident.name != kw::PathRoot {
-            s.push_str(&seg.ident.as_str());
+            s.push_str(seg.ident.as_str());
         }
     }
     s

src/librustdoc/formats/cache.rs

@@ -150,8 +150,7 @@ impl Cache {
 
             let name = e.name(tcx);
             let render_options = &cx.render_options;
-            let extern_url =
+            let extern_url = render_options.extern_html_root_urls.get(name.as_str()).map(|u| &**u);
-                render_options.extern_html_root_urls.get(&*name.as_str()).map(|u| &**u);
             let extern_url_takes_precedence = render_options.extern_html_root_takes_precedence;
             let dst = &render_options.output;
             let location = e.location(extern_url, extern_url_takes_precedence, dst, tcx);

src/librustdoc/formats/renderer.rs

@@ -90,7 +90,7 @@ crate fn run_format<'tcx, T: FormatRenderer<'tcx>>(
         // FIXME: checking `item.name.is_some()` is very implicit and leads to lots of special
         // cases. Use an explicit match instead.
         } else if item.name.is_some() && !item.is_extern_crate() {
-            prof.generic_activity_with_arg("render_item", &*item.name.unwrap_or(unknown).as_str())
+            prof.generic_activity_with_arg("render_item", item.name.unwrap_or(unknown).as_str())
                 .run(|| cx.item(item))?;
         }
     }

src/librustdoc/html/format.rs

@@ -175,7 +175,7 @@ impl clean::GenericParamDef {
                 Ok(())
             }
             clean::GenericParamDefKind::Type { bounds, default, .. } => {
-                f.write_str(&*self.name.as_str())?;
+                f.write_str(self.name.as_str())?;
 
                 if !bounds.is_empty() {
                     if f.alternate() {
@@ -638,7 +638,7 @@ fn resolved_path<'cx>(
                 last.name.to_string()
             }
         } else {
-            anchor(did, &*last.name.as_str(), cx).to_string()
+            anchor(did, last.name.as_str(), cx).to_string()
         };
         write!(w, "{}{}", path, last.args.print(cx))?;
     }
@@ -667,20 +667,18 @@ fn primitive_link(
                 needs_termination = true;
             }
             Some(&def_id) => {
-                let cname_str;
+                let cname_sym;
                 let loc = match m.extern_locations[&def_id.krate] {
                     ExternalLocation::Remote(ref s) => {
-                        cname_str =
+                        cname_sym = ExternalCrate { crate_num: def_id.krate }.name(cx.tcx());
-                            ExternalCrate { crate_num: def_id.krate }.name(cx.tcx()).as_str();
+                        Some(vec![s.trim_end_matches('/'), cname_sym.as_str()])
-                        Some(vec![s.trim_end_matches('/'), &cname_str[..]])
                     }
                     ExternalLocation::Local => {
-                        cname_str =
+                        cname_sym = ExternalCrate { crate_num: def_id.krate }.name(cx.tcx());
-                            ExternalCrate { crate_num: def_id.krate }.name(cx.tcx()).as_str();
+                        Some(if cx.current.first().map(|x| &x[..]) == Some(cname_sym.as_str()) {
-                        Some(if cx.current.first().map(|x| &x[..]) == Some(&cname_str[..]) {
                             iter::repeat("..").take(cx.current.len() - 1).collect()
                         } else {
-                            let cname = iter::once(&cname_str[..]);
+                            let cname = iter::once(cname_sym.as_str());
                             iter::repeat("..").take(cx.current.len()).chain(cname).collect()
                         })
                     }
@@ -775,7 +773,7 @@ fn fmt_type<'cx>(
         clean::Primitive(clean::PrimitiveType::Never) => {
             primitive_link(f, PrimitiveType::Never, "!", cx)
         }
-        clean::Primitive(prim) => primitive_link(f, prim, &*prim.as_sym().as_str(), cx),
+        clean::Primitive(prim) => primitive_link(f, prim, prim.as_sym().as_str(), cx),
         clean::BareFunction(ref decl) => {
             if f.alternate() {
                 write!(
@@ -1271,7 +1269,7 @@ impl clean::Visibility {
                     debug!("path={:?}", path);
                     // modified from `resolved_path()` to work with `DefPathData`
                     let last_name = path.data.last().unwrap().data.get_opt_name().unwrap();
-                    let anchor = anchor(vis_did, &last_name.as_str(), cx).to_string();
+                    let anchor = anchor(vis_did, last_name.as_str(), cx).to_string();
 
                     let mut s = "pub(in ".to_owned();
                     for seg in &path.data[..path.data.len() - 1] {
@@ -1402,9 +1400,9 @@ impl clean::ImportSource {
                 for seg in &self.path.segments[..self.path.segments.len() - 1] {
                     write!(f, "{}::", seg.name)?;
                 }
-                let name = self.path.last_name();
+                let name = self.path.last();
                 if let hir::def::Res::PrimTy(p) = self.path.res {
-                    primitive_link(f, PrimitiveType::from(p), &*name, cx)?;
+                    primitive_link(f, PrimitiveType::from(p), name.as_str(), cx)?;
                 } else {
                     write!(f, "{}", name)?;
                 }
@@ -1420,7 +1418,7 @@ impl clean::TypeBinding {
         cx: &'a Context<'tcx>,
     ) -> impl fmt::Display + 'a + Captures<'tcx> {
         display_fn(move |f| {
-            f.write_str(&*self.name.as_str())?;
+            f.write_str(self.name.as_str())?;
             match self.kind {
                 clean::TypeBindingKind::Equality { ref ty } => {
                     if f.alternate() {

src/librustdoc/html/render/context.rs

@@ -180,7 +180,7 @@ impl<'tcx> Context<'tcx> {
     fn render_item(&self, it: &clean::Item, is_module: bool) -> String {
         let mut title = String::new();
         if !is_module {
-            title.push_str(&it.name.unwrap().as_str());
+            title.push_str(it.name.unwrap().as_str());
         }
         if !it.is_primitive() && !it.is_keyword() {
             if !is_module {
@@ -315,7 +315,7 @@ impl<'tcx> Context<'tcx> {
         };
         let file = &file;
 
-        let symbol;
+        let krate_sym;
         let (krate, path) = if cnum == LOCAL_CRATE {
             if let Some(path) = self.shared.local_sources.get(file) {
                 (self.shared.layout.krate.as_str(), path)
@@ -343,8 +343,8 @@ impl<'tcx> Context<'tcx> {
             let mut fname = file.file_name().expect("source has no filename").to_os_string();
             fname.push(".html");
             path.push_str(&fname.to_string_lossy());
-            symbol = krate.as_str();
+            krate_sym = krate;
-            (&*symbol, &path)
+            (krate_sym.as_str(), &path)
         };
 
         let anchor = if with_lines {
@@ -549,7 +549,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
 
     fn after_krate(&mut self) -> Result<(), Error> {
         let crate_name = self.tcx().crate_name(LOCAL_CRATE);
-        let final_file = self.dst.join(&*crate_name.as_str()).join("all.html");
+        let final_file = self.dst.join(crate_name.as_str()).join("all.html");
         let settings_file = self.dst.join("settings.html");
 
         let mut root_path = self.dst.to_str().expect("invalid path").to_owned();
@@ -619,9 +619,9 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
         if let Some(ref redirections) = self.shared.redirections {
             if !redirections.borrow().is_empty() {
                 let redirect_map_path =
-                    self.dst.join(&*crate_name.as_str()).join("redirect-map.json");
+                    self.dst.join(crate_name.as_str()).join("redirect-map.json");
                 let paths = serde_json::to_string(&*redirections.borrow()).unwrap();
-                self.shared.ensure_dir(&self.dst.join(&*crate_name.as_str()))?;
+                self.shared.ensure_dir(&self.dst.join(crate_name.as_str()))?;
                 self.shared.fs.write(redirect_map_path, paths)?;
             }
         }
@@ -703,7 +703,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
         if !buf.is_empty() {
             let name = item.name.as_ref().unwrap();
             let item_type = item.type_();
-            let file_name = &item_path(item_type, &name.as_str());
+            let file_name = &item_path(item_type, name.as_str());
             self.shared.ensure_dir(&self.dst)?;
             let joint_dst = self.dst.join(file_name);
             self.shared.fs.write(joint_dst, buf)?;

src/librustdoc/html/render/mod.rs

@@ -640,9 +640,9 @@ fn short_item_info(
         // We display deprecation messages for #[deprecated] and #[rustc_deprecated]
         // but only display the future-deprecation messages for #[rustc_deprecated].
         let mut message = if let Some(since) = since {
-            let since = &since.as_str();
+            let since = since.as_str();
             if !stability::deprecation_in_effect(&depr) {
-                if *since == "TBD" {
+                if since == "TBD" {
                     String::from("Deprecating in a future Rust version")
                 } else {
                     format!("Deprecating in {}", Escape(since))
@@ -658,7 +658,7 @@ fn short_item_info(
             let note = note.as_str();
             let mut ids = cx.id_map.borrow_mut();
             let html = MarkdownHtml(
-                &note,
+                note,
                 &mut ids,
                 error_codes,
                 cx.shared.edition(),
@@ -683,7 +683,7 @@ fn short_item_info(
         let mut message =
             "<span class=\"emoji\">🔬</span> This is a nightly-only experimental API.".to_owned();
 
-        let mut feature = format!("<code>{}</code>", Escape(&feature.as_str()));
+        let mut feature = format!("<code>{}</code>", Escape(feature.as_str()));
         if let (Some(url), Some(issue)) = (&cx.shared.issue_tracker_base_url, issue) {
             feature.push_str(&format!(
                 "&nbsp;<a href=\"{url}{issue}\">#{issue}</a>",
@@ -1414,7 +1414,7 @@ fn render_impl(
                     let source_id = trait_
                         .and_then(|trait_| {
                             trait_.items.iter().find(|item| {
-                                item.name.map(|n| n.as_str().eq(&name.as_str())).unwrap_or(false)
+                                item.name.map(|n| n.as_str().eq(name.as_str())).unwrap_or(false)
                             })
                         })
                         .map(|item| format!("{}.{}", item.type_(), name));

src/librustdoc/html/render/print_item.rs

@@ -136,7 +136,7 @@ pub(super) fn print_item(
         page: page,
         static_root_path: page.get_static_root_path(),
         typ: typ,
-        name: &item.name.as_ref().unwrap().as_str(),
+        name: item.name.as_ref().unwrap().as_str(),
         item_type: &item.type_().to_string(),
         path_components: path_components,
         stability_since_raw: &stability_since_raw,
@@ -239,9 +239,9 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
                 (true, false) => return Ordering::Greater,
             }
         }
-        let lhs = i1.name.unwrap_or(kw::Empty).as_str();
+        let lhs = i1.name.unwrap_or(kw::Empty);
-        let rhs = i2.name.unwrap_or(kw::Empty).as_str();
+        let rhs = i2.name.unwrap_or(kw::Empty);
-        compare_names(&lhs, &rhs)
+        compare_names(lhs.as_str(), rhs.as_str())
     }
 
     if cx.shared.sort_modules_alphabetically {
@@ -315,7 +315,7 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
                         w,
                         "<div class=\"item-left\"><code>{}extern crate {} as {};",
                         myitem.visibility.print_with_space(myitem.def_id, cx),
-                        anchor(myitem.def_id.expect_def_id(), &*src.as_str(), cx),
+                        anchor(myitem.def_id.expect_def_id(), src.as_str(), cx),
                         myitem.name.as_ref().unwrap(),
                     ),
                     None => write!(
@@ -324,7 +324,7 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
                         myitem.visibility.print_with_space(myitem.def_id, cx),
                         anchor(
                             myitem.def_id.expect_def_id(),
-                            &*myitem.name.as_ref().unwrap().as_str(),
+                            myitem.name.as_ref().unwrap().as_str(),
                             cx
                         ),
                     ),
@@ -405,7 +405,7 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
                     add = add,
                     stab = stab.unwrap_or_default(),
                     unsafety_flag = unsafety_flag,
-                    href = item_path(myitem.type_(), &myitem.name.unwrap().as_str()),
+                    href = item_path(myitem.type_(), myitem.name.unwrap().as_str()),
                     title = [full_path(cx, myitem), myitem.type_().to_string()]
                         .iter()
                         .filter_map(|s| if !s.is_empty() { Some(s.as_str()) } else { None })
@@ -1308,7 +1308,7 @@ fn item_struct(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::St
             document_non_exhaustive(w, it);
             for (index, (field, ty)) in fields.enumerate() {
                 let field_name =
-                    field.name.map_or_else(|| index.to_string(), |sym| (*sym.as_str()).to_string());
+                    field.name.map_or_else(|| index.to_string(), |sym| sym.as_str().to_string());
                 let id = cx.derive_id(format!("{}.{}", ItemType::StructField, field_name));
                 write!(
                     w,
@@ -1410,7 +1410,7 @@ crate fn compare_names(mut lhs: &str, mut rhs: &str) -> Ordering {
 pub(super) fn full_path(cx: &Context<'_>, item: &clean::Item) -> String {
     let mut s = cx.current.join("::");
     s.push_str("::");
-    s.push_str(&item.name.unwrap().as_str());
+    s.push_str(item.name.unwrap().as_str());
     s
 }
 

src/librustdoc/html/render/write_shared.rs

@@ -418,7 +418,7 @@ pub(super) fn write_shared(
         let dst = cx.dst.join(&format!("source-files{}.js", cx.shared.resource_suffix));
         let make_sources = || {
             let (mut all_sources, _krates) =
-                try_err!(collect(&dst, &krate.name(cx.tcx()).as_str(), "sourcesIndex"), &dst);
+                try_err!(collect(&dst, krate.name(cx.tcx()).as_str(), "sourcesIndex"), &dst);
             all_sources.push(format!(
                 "sourcesIndex[\"{}\"] = {};",
                 &krate.name(cx.tcx()),
@@ -437,7 +437,7 @@ pub(super) fn write_shared(
     // Update the search index and crate list.
     let dst = cx.dst.join(&format!("search-index{}.js", cx.shared.resource_suffix));
     let (mut all_indexes, mut krates) =
-        try_err!(collect_json(&dst, &krate.name(cx.tcx()).as_str()), &dst);
+        try_err!(collect_json(&dst, krate.name(cx.tcx()).as_str()), &dst);
     all_indexes.push(search_index);
     krates.push(krate.name(cx.tcx()).to_string());
     krates.sort();
@@ -575,7 +575,7 @@ pub(super) fn write_shared(
         mydst.push(&format!("{}.{}.js", remote_item_type, remote_path[remote_path.len() - 1]));
 
         let (mut all_implementors, _) =
-            try_err!(collect(&mydst, &krate.name(cx.tcx()).as_str(), "implementors"), &mydst);
+            try_err!(collect(&mydst, krate.name(cx.tcx()).as_str(), "implementors"), &mydst);
         all_implementors.push(implementors);
         // Sort the implementors by crate so the file will be generated
         // identically even with rustdoc running in parallel.

src/librustdoc/html/sources.rs

@@ -19,7 +19,7 @@ use std::path::{Component, Path, PathBuf};
 crate fn render(cx: &mut Context<'_>, krate: &clean::Crate) -> Result<(), Error> {
     info!("emitting source files");
 
-    let dst = cx.dst.join("src").join(&*krate.name(cx.tcx()).as_str());
+    let dst = cx.dst.join("src").join(krate.name(cx.tcx()).as_str());
     cx.shared.ensure_dir(&dst)?;
 
     let mut collector = SourceCollector { dst, cx, emitted_local_sources: FxHashSet::default() };

src/librustdoc/json/conversions.rs

@@ -609,7 +609,7 @@ impl FromWithTcx<clean::Import> for Import {
             },
             Glob => Import {
                 source: import.source.path.whole_name(),
-                name: import.source.path.last_name().to_string(),
+                name: import.source.path.last().to_string(),
                 id: import.source.did.map(ItemId::from).map(from_item_id),
                 glob: true,
             },

src/librustdoc/passes/collect_intra_doc_links.rs

@@ -2153,8 +2153,8 @@ fn privacy_error(cx: &DocContext<'_>, diag_info: &DiagnosticInfo<'_>, path_str:
     let sym;
     let item_name = match diag_info.item.name {
         Some(name) => {
-            sym = name.as_str();
+            sym = name;
-            &*sym
+            sym.as_str()
         }
         None => "<unknown>",
     };

src/test/ui-fulldeps/auxiliary/lint-group-plugin-test.rs

@@ -21,7 +21,7 @@ declare_lint_pass!(Pass => [TEST_LINT, PLEASE_LINT]);
 
 impl<'tcx> LateLintPass<'tcx> for Pass {
     fn check_item(&mut self, cx: &LateContext, it: &rustc_hir::Item) {
-        match &*it.ident.as_str() {
+        match it.ident.as_str() {
             "lintme" => cx.lint(TEST_LINT, |lint| {
                 lint.build("item is named 'lintme'").set_span(it.span).emit()
             }),

src/tools/clippy/clippy_lints/src/attrs.rs

@@ -17,7 +17,7 @@ use rustc_semver::RustcVersion;
 use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
 use rustc_span::source_map::Span;
 use rustc_span::sym;
-use rustc_span::symbol::{Symbol, SymbolStr};
+use rustc_span::symbol::Symbol;
 use semver::Version;
 
 static UNIX_SYSTEMS: &[&str] = &[
@@ -310,8 +310,8 @@ impl<'tcx> LateLintPass<'tcx> for Attributes {
                                             || is_word(lint, sym::deprecated)
                                             || is_word(lint, sym!(unreachable_pub))
                                             || is_word(lint, sym!(unused))
-                                            || extract_clippy_lint(lint).map_or(false, |s| s == "wildcard_imports")
+                                            || extract_clippy_lint(lint).map_or(false, |s| s.as_str() == "wildcard_imports")
-                                            || extract_clippy_lint(lint).map_or(false, |s| s == "enum_glob_use")
+                                            || extract_clippy_lint(lint).map_or(false, |s| s.as_str() == "enum_glob_use")
                                         {
                                             return;
                                         }
@@ -370,7 +370,7 @@ impl<'tcx> LateLintPass<'tcx> for Attributes {
 }
 
 /// Returns the lint name if it is clippy lint.
-fn extract_clippy_lint(lint: &NestedMetaItem) -> Option<SymbolStr> {
+fn extract_clippy_lint(lint: &NestedMetaItem) -> Option<Symbol> {
     if_chain! {
         if let Some(meta_item) = lint.meta_item();
         if meta_item.path.segments.len() > 1;
@@ -378,7 +378,7 @@ fn extract_clippy_lint(lint: &NestedMetaItem) -> Option<SymbolStr> {
         if tool_name.name == sym::clippy;
         then {
             let lint_name = meta_item.path.segments.last().unwrap().ident.name;
-            return Some(lint_name.as_str());
+            return Some(lint_name);
         }
     }
     None
@@ -387,7 +387,7 @@ fn extract_clippy_lint(lint: &NestedMetaItem) -> Option<SymbolStr> {
 fn check_clippy_lint_names(cx: &LateContext<'_>, name: Symbol, items: &[NestedMetaItem]) {
     for lint in items {
         if let Some(lint_name) = extract_clippy_lint(lint) {
-            if lint_name == "restriction" && name != sym::allow {
+            if lint_name.as_str() == "restriction" && name != sym::allow {
                 span_lint_and_help(
                     cx,
                     BLANKET_CLIPPY_RESTRICTION_LINTS,
@@ -486,7 +486,7 @@ fn check_attrs(cx: &LateContext<'_>, span: Span, name: Symbol, attrs: &[Attribut
 
 fn check_semver(cx: &LateContext<'_>, span: Span, lit: &Lit) {
     if let LitKind::Str(is, _) = lit.kind {
-        if Version::parse(&is.as_str()).is_ok() {
+        if Version::parse(is.as_str()).is_ok() {
             return;
         }
     }
@@ -619,7 +619,7 @@ fn check_mismatched_target_os(cx: &EarlyContext<'_>, attr: &Attribute) {
                     MetaItemKind::Word => {
                         if_chain! {
                             if let Some(ident) = meta.ident();
-                            if let Some(os) = find_os(&*ident.name.as_str());
+                            if let Some(os) = find_os(ident.name.as_str());
                             then {
                                 mismatched.push((os, ident.span));
                             }

src/tools/clippy/clippy_lints/src/booleans.rs

@@ -272,7 +272,7 @@ fn simplify_not(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<String> {
                 .copied()
                 .flat_map(|(a, b)| vec![(a, b), (b, a)])
                 .find(|&(a, _)| {
-                    let path: &str = &path.ident.name.as_str();
+                    let path: &str = path.ident.name.as_str();
                     a == path
                 })
                 .and_then(|(_, neg_method)| Some(format!("{}.{}()", snippet_opt(cx, args[0].span)?, neg_method)))

src/tools/clippy/clippy_lints/src/checked_conversions.rs

@@ -321,8 +321,8 @@ fn get_implementing_type<'a>(path: &QPath<'_>, candidates: &'a [&str], function:
         if let TyKind::Path(QPath::Resolved(None, tp)) = &ty.kind;
         if let [int] = &*tp.segments;
         then {
-            let name = &int.ident.name.as_str();
+            let name = int.ident.name.as_str();
-            candidates.iter().find(|c| name == *c).copied()
+            candidates.iter().find(|c| &name == *c).copied()
         } else {
             None
         }
@@ -335,8 +335,8 @@ fn int_ty_to_sym<'tcx>(path: &QPath<'_>) -> Option<&'tcx str> {
         if let QPath::Resolved(_, path) = *path;
         if let [ty] = &*path.segments;
         then {
-            let name = &ty.ident.name.as_str();
+            let name = ty.ident.name.as_str();
-            INTS.iter().find(|c| name == *c).copied()
+            INTS.iter().find(|c| &name == *c).copied()
         } else {
             None
         }

src/tools/clippy/clippy_lints/src/doc.rs

@@ -437,7 +437,7 @@ fn check_attrs<'a>(cx: &LateContext<'_>, valid_idents: &FxHashSet<String>, attrs
 
     for attr in attrs {
         if let AttrKind::DocComment(comment_kind, comment) = attr.kind {
-            let (comment, current_spans) = strip_doc_comment_decoration(&comment.as_str(), comment_kind, attr.span);
+            let (comment, current_spans) = strip_doc_comment_decoration(comment.as_str(), comment_kind, attr.span);
             spans.extend_from_slice(&current_spans);
             doc.push_str(&comment);
         } else if attr.has_name(sym::doc) {

src/tools/clippy/clippy_lints/src/duration_subsec.rs

@@ -49,7 +49,7 @@ impl<'tcx> LateLintPass<'tcx> for DurationSubsec {
             if match_type(cx, cx.typeck_results().expr_ty(&args[0]).peel_refs(), &paths::DURATION);
             if let Some((Constant::Int(divisor), _)) = constant(cx, cx.typeck_results(), right);
             then {
-                let suggested_fn = match (method_path.ident.as_str().as_ref(), divisor) {
+                let suggested_fn = match (method_path.ident.as_str(), divisor) {
                     ("subsec_micros", 1_000) | ("subsec_nanos", 1_000_000) => "subsec_millis",
                     ("subsec_nanos", 1_000) => "subsec_micros",
                     _ => return,

src/tools/clippy/clippy_lints/src/enum_variants.rs

@@ -153,7 +153,7 @@ fn check_variant(
             );
         }
     }
-    let first = &def.variants[0].ident.name.as_str();
+    let first = def.variants[0].ident.name.as_str();
     let mut pre = &first[..str_utils::camel_case_until(&*first).byte_index];
     let mut post = &first[str_utils::camel_case_start(&*first).byte_index..];
     for var in def.variants {