Simplify various Symbol use points.

Including removing a bunch of unnecessary `.as_str()` calls, and a bunch
of unnecessary sigils.

Author: nnethercote

Diff for: src/librustc/hir/lowering.rs

@@ -3423,7 +3423,7 @@ pub fn is_range_literal(sess: &Session, expr: &hir::Expr) -> bool {
         ExprKind::Call(ref func, _) => {
             if let ExprKind::Path(QPath::TypeRelative(ref ty, ref segment)) = func.kind {
                 if let TyKind::Path(QPath::Resolved(None, ref path)) = ty.kind {
-                    let new_call = segment.ident.as_str() == "new";
+                    let new_call = segment.ident.name == sym::new;
                     return is_range_path(&path) && is_lit(sess, &expr.span) && new_call;
                 }
             }

Diff for: src/librustc/mir/mono.rs

@@ -486,7 +486,7 @@ impl CodegenUnitNameBuilder<'tcx> {
         if self.tcx.sess.opts.debugging_opts.human_readable_cgu_names {
             cgu_name
         } else {
-            let cgu_name = &cgu_name.as_str()[..];
+            let cgu_name = &cgu_name.as_str();
             Symbol::intern(&CodegenUnit::mangle_name(cgu_name))
         }
     }

Diff for: src/librustc/traits/error_reporting.rs

@@ -1130,7 +1130,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                     let restrict_msg = "consider further restricting this bound";
                     let param_name = self_ty.to_string();
                     for param in generics.params.iter().filter(|p| {
-                        &param_name == std::convert::AsRef::<str>::as_ref(&p.name.ident().as_str())
+                        p.name.ident().as_str() == param_name
                     }) {
                         if param_name.starts_with("impl ") {
                             // `impl Trait` in argument:

Diff for: src/librustc_codegen_llvm/attributes.rs

@@ -314,7 +314,7 @@ pub fn from_fn_attrs(
             codegen_fn_attrs.target_features
                 .iter()
                 .map(|f| {
-                    let feature = &*f.as_str();
+                    let feature = &f.as_str();
                     format!("+{}", llvm_util::to_llvm_feature(cx.tcx.sess, feature))
                 })
         )

Diff for: src/librustc_codegen_llvm/debuginfo/namespace.rs

@@ -34,11 +34,11 @@ pub fn item_namespace(cx: &CodegenCx<'ll, '_>, def_id: DefId) -> &'ll DIScope {
     });
 
     let namespace_name = match def_key.disambiguated_data.data {
-        DefPathData::CrateRoot => cx.tcx.crate_name(def_id.krate).as_str(),
-        data => data.as_symbol().as_str()
+        DefPathData::CrateRoot => cx.tcx.crate_name(def_id.krate),
+        data => data.as_symbol()
     };
 
-    let namespace_name = SmallCStr::new(&namespace_name);
+    let namespace_name = SmallCStr::new(&namespace_name.as_str());
 
     let scope = unsafe {
         llvm::LLVMRustDIBuilderCreateNameSpace(

Diff for: src/librustc_codegen_ssa/back/symbol_export.rs

@@ -129,9 +129,9 @@ fn reachable_non_generics_provider(
                 //
                 // In general though we won't link right if these
                 // symbols are stripped, and LTO currently strips them.
-                if &*name == "rust_eh_personality" ||
-                   &*name == "rust_eh_register_frames" ||
-                   &*name == "rust_eh_unregister_frames" {
+                if name == "rust_eh_personality" ||
+                   name == "rust_eh_register_frames" ||
+                   name == "rust_eh_unregister_frames" {
                     SymbolExportLevel::C
                 } else {
                     SymbolExportLevel::Rust

Diff for: src/librustc_codegen_utils/symbol_names/legacy.rs

@@ -121,9 +121,10 @@ fn get_symbol_hash<'tcx>(
         substs.hash_stable(&mut hcx, &mut hasher);
 
         if let Some(instantiating_crate) = instantiating_crate {
-            (&tcx.original_crate_name(instantiating_crate).as_str()[..])
+            tcx.original_crate_name(instantiating_crate).as_str()
+                .hash_stable(&mut hcx, &mut hasher);
+            tcx.crate_disambiguator(instantiating_crate)
                 .hash_stable(&mut hcx, &mut hasher);
-            (&tcx.crate_disambiguator(instantiating_crate)).hash_stable(&mut hcx, &mut hasher);
         }
 
         // We want to avoid accidental collision between different types of instances.

Diff for: src/librustc_incremental/assert_module_sources.rs

@@ -67,7 +67,7 @@ impl AssertModuleSource<'tcx> {
         } else if attr.check_name(ATTR_PARTITION_CODEGENED) {
             (CguReuse::No, ComparisonKind::Exact)
         } else if attr.check_name(ATTR_EXPECTED_CGU_REUSE) {
-            match &self.field(attr, sym::kind).as_str()[..] {
+            match &*self.field(attr, sym::kind).as_str() {
                 "no" => (CguReuse::No, ComparisonKind::Exact),
                 "pre-lto" => (CguReuse::PreLto, ComparisonKind::Exact),
                 "post-lto" => (CguReuse::PostLto, ComparisonKind::Exact),

Diff for: src/librustc_incremental/persist/dirty_clean.rs

@@ -303,7 +303,7 @@ impl DirtyCleanVisitor<'tcx> {
         for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
             if item.check_name(LABEL) {
                 let value = expect_associated_value(self.tcx, &item);
-                return Some(self.resolve_labels(&item, value.as_str().as_ref()));
+                return Some(self.resolve_labels(&item, &value.as_str()));
             }
         }
         None
@@ -314,7 +314,7 @@ impl DirtyCleanVisitor<'tcx> {
         for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
             if item.check_name(EXCEPT) {
                 let value = expect_associated_value(self.tcx, &item);
-                return self.resolve_labels(&item, value.as_str().as_ref());
+                return self.resolve_labels(&item, &value.as_str());
             }
         }
         // if no `label` or `except` is given, only the node's group are asserted

Diff for: src/librustc_lint/builtin.rs

@@ -1476,14 +1476,12 @@ impl KeywordIdents {
         let mut lint = cx.struct_span_lint(
             KEYWORD_IDENTS,
             ident.span,
-            &format!("`{}` is a keyword in the {} edition",
-                     ident.as_str(),
-                     next_edition),
+            &format!("`{}` is a keyword in the {} edition", ident, next_edition),
         );
         lint.span_suggestion(
             ident.span,
             "you can use a raw identifier to stay compatible",
-            format!("r#{}", ident.as_str()),
+            format!("r#{}", ident),
             Applicability::MachineApplicable,
         );
         lint.emit()

Diff for: src/librustc_metadata/creader.rs

@@ -121,7 +121,7 @@ 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).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`.
                 let found = entry.locations.iter().filter_map(|l| l.as_ref()).any(|l| {
                     let l = fs::canonicalize(l).ok();

Diff for: src/librustc_metadata/native_libs.rs

@@ -68,7 +68,7 @@ impl 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" => cstore::NativeStatic,
                         "static-nobundle" => cstore::NativeStaticNobundle,
                         "dylib" => cstore::NativeUnknown,

Diff for: src/librustc_mir/borrow_check/conflict_errors.rs

@@ -974,7 +974,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         let mut err = self.cannot_borrow_across_destructor(borrow_span);
 
         let what_was_dropped = match self.describe_place(place.as_ref()) {
-            Some(name) => format!("`{}`", name.as_str()),
+            Some(name) => format!("`{}`", name),
             None => String::from("temporary value"),
         };
 

Diff for: src/librustc_mir/interpret/intrinsics.rs

@@ -95,7 +95,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     ) -> InterpResult<'tcx, bool> {
         let substs = instance.substs;
 
-        let intrinsic_name = &self.tcx.item_name(instance.def_id()).as_str()[..];
+        let intrinsic_name = &*self.tcx.item_name(instance.def_id()).as_str();
         match intrinsic_name {
             "caller_location" => {
                 let caller = self.tcx.sess.source_map().lookup_char_pos(span.lo());

Diff for: src/librustc_mir/transform/check_unsafety.rs

@@ -642,17 +642,17 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: DefId) {
                 struct_span_err!(
                     tcx.sess, source_info.span, E0133,
                     "{} is unsafe and requires unsafe function or block", description)
-                    .span_label(source_info.span, &description.as_str()[..])
-                    .note(&details.as_str()[..])
+                    .span_label(source_info.span, &*description.as_str())
+                    .note(&details.as_str())
                     .emit();
             }
             UnsafetyViolationKind::ExternStatic(lint_hir_id) => {
                 tcx.lint_node_note(SAFE_EXTERN_STATICS,
                               lint_hir_id,
                               source_info.span,
                               &format!("{} is unsafe and requires unsafe function or block \
-                                        (error E0133)", &description.as_str()[..]),
-                              &details.as_str()[..]);
+                                        (error E0133)", description),
+                              &details.as_str());
             }
             UnsafetyViolationKind::BorrowPacked(lint_hir_id) => {
                 if let Some(impl_def_id) = builtin_derive_def_id(tcx, def_id) {
@@ -662,8 +662,8 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: DefId) {
                                   lint_hir_id,
                                   source_info.span,
                                   &format!("{} is unsafe and requires unsafe function or block \
-                                            (error E0133)", &description.as_str()[..]),
-                                  &details.as_str()[..]);
+                                            (error E0133)", description),
+                                  &details.as_str());
                 }
             }
         }

Diff for: src/librustc_mir/transform/qualify_consts.rs

@@ -537,7 +537,7 @@ impl Qualif for IsNotPromotable {
                     Abi::RustIntrinsic |
                     Abi::PlatformIntrinsic => {
                         assert!(!cx.tcx.is_const_fn(def_id));
-                        match &cx.tcx.item_name(def_id).as_str()[..] {
+                        match &*cx.tcx.item_name(def_id).as_str() {
                             | "size_of"
                             | "min_align_of"
                             | "needs_drop"
@@ -1476,7 +1476,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Checker<'a, 'tcx> {
                         Abi::RustIntrinsic |
                         Abi::PlatformIntrinsic => {
                             assert!(!self.tcx.is_const_fn(def_id));
-                            match &self.tcx.item_name(def_id).as_str()[..] {
+                            match &*self.tcx.item_name(def_id).as_str() {
                                 // special intrinsic that can be called diretly without an intrinsic
                                 // feature gate needs a language feature gate
                                 "transmute" => {

Diff for: src/librustc_mir/transform/qualify_min_const_fn.rs

@@ -402,7 +402,7 @@ fn check_terminator(
 ///
 /// Adding more intrinsics requires sign-off from @rust-lang/lang.
 fn is_intrinsic_whitelisted(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
-    match &tcx.item_name(def_id).as_str()[..] {
+    match &*tcx.item_name(def_id).as_str() {
         | "size_of"
         | "min_align_of"
         | "needs_drop"

Diff for: src/librustc_resolve/late.rs

@@ -1876,7 +1876,7 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
                                     None
                                 }
                             });
-                            find_best_match_for_name(names, &*ident.as_str(), None)
+                            find_best_match_for_name(names, &ident.as_str(), None)
                         });
                         self.r.record_partial_res(expr.id, PartialRes::new(Res::Err));
                         self.r.report_error(

Diff for: src/librustc_typeck/check/demand.rs

@@ -308,7 +308,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }) = parent {
                 if let Ok(src) = cm.span_to_snippet(sp) {
                     for field in fields {
-                        if field.ident.as_str() == src.as_str() && field.is_shorthand {
+                        if field.ident.as_str() == src && field.is_shorthand {
                             return true;
                         }
                     }
@@ -409,13 +409,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     let mut sugg_sp = sp;
                     if let hir::ExprKind::MethodCall(segment, _sp, args) = &expr.kind {
                         let clone_trait = self.tcx.lang_items().clone_trait().unwrap();
-                        if let ([arg], Some(true), "clone") = (
+                        if let ([arg], Some(true), sym::clone) = (
                             &args[..],
                             self.tables.borrow().type_dependent_def_id(expr.hir_id).map(|did| {
                                 let ai = self.tcx.associated_item(did);
                                 ai.container == ty::TraitContainer(clone_trait)
                             }),
-                            &segment.ident.as_str()[..],
+                            segment.ident.name,
                         ) {
                             // If this expression had a clone call when suggesting borrowing
                             // we want to suggest removing it because it'd now be unecessary.

Diff for: src/librustc_typeck/check/method/suggest.rs

@@ -835,11 +835,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                     sp,
                                     &message(format!(
                                         "restrict type parameter `{}` with",
-                                        param.name.ident().as_str(),
+                                        param.name.ident(),
                                     )),
                                     candidates.iter().map(|t| format!(
                                         "{}{} {}{}",
-                                        param.name.ident().as_str(),
+                                        param.name.ident(),
                                         if impl_trait { " +" } else { ":" },
                                         self.tcx.def_path_str(t.def_id),
                                         if has_bounds.is_some() { " + "} else { "" },

Diff for: src/librustc_typeck/check/pat.rs

@@ -978,7 +978,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     );
 
                     // we don't want to throw `E0027` in case we have thrown `E0026` for them
-                    unmentioned_fields.retain(|&x| x.as_str() != suggested_name.as_str());
+                    unmentioned_fields.retain(|&x| x.name != suggested_name);
                 }
             }
         }

Diff for: src/librustc_typeck/collect.rs

@@ -2404,7 +2404,7 @@ fn compute_sig_of_foreign_fn_decl<'tcx>(
     abi: abi::Abi,
 ) -> ty::PolyFnSig<'tcx> {
     let unsafety = if abi == abi::Abi::RustIntrinsic {
-        intrinsic_operation_unsafety(&*tcx.item_name(def_id).as_str())
+        intrinsic_operation_unsafety(&tcx.item_name(def_id).as_str())
     } else {
         hir::Unsafety::Unsafe
     };

Diff for: src/librustdoc/clean/cfg.rs

@@ -404,7 +404,7 @@ impl<'a> fmt::Display for Html<'a> {
                 if !human_readable.is_empty() {
                     fmt.write_str(human_readable)
                 } else if let Some(v) = value {
-                    write!(fmt, "<code>{}=\"{}\"</code>", Escape(n), Escape(&*v.as_str()))
+                    write!(fmt, "<code>{}=\"{}\"</code>", Escape(n), Escape(&v.as_str()))
                 } else {
                     write!(fmt, "<code>{}</code>", Escape(n))
                 }

Diff for: src/librustdoc/clean/mod.rs

@@ -3704,7 +3704,7 @@ 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

Diff for: src/librustdoc/html/render.rs

@@ -2964,7 +2964,7 @@ fn render_attribute(attr: &ast::MetaItem) -> Option<String> {
     if attr.is_word() {
         Some(path)
     } else if let Some(v) = attr.value_str() {
-        Some(format!("{} = {:?}", path, v.as_str()))
+        Some(format!("{} = {:?}", path, v))
     } else if let Some(values) = attr.meta_item_list() {
         let display: Vec<_> = values.iter().filter_map(|attr| {
             attr.meta_item().and_then(|mi| render_attribute(mi))

Diff for: src/libsyntax/ast.rs

@@ -90,7 +90,7 @@ impl fmt::Debug for Lifetime {
 
 impl fmt::Display for Lifetime {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.ident.name.as_str())
+        write!(f, "{}", self.ident.name)
     }
 }
 

Diff for: src/libsyntax/feature_gate/check.rs

@@ -730,7 +730,7 @@ pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
             }
 
             if let Some(allowed) = allow_features.as_ref() {
-                if allowed.iter().find(|&f| f == &name.as_str() as &str).is_none() {
+                if allowed.iter().find(|&f| name.as_str() == *f).is_none() {
                     span_err!(span_handler, mi.span(), E0725,
                               "the feature `{}` is not in the list of allowed features",
                               name);

Diff for: src/libsyntax/parse/literal.rs

@@ -134,9 +134,9 @@ impl LitKind {
         let (kind, symbol, suffix) = match *self {
             LitKind::Str(symbol, ast::StrStyle::Cooked) => {
                 // Don't re-intern unless the escaped string is different.
-                let s: &str = &symbol.as_str();
+                let s = symbol.as_str();
                 let escaped = s.escape_default().to_string();
-                let symbol = if escaped == *s { symbol } else { Symbol::intern(&escaped) };
+                let symbol = if s == escaped { symbol } else { Symbol::intern(&escaped) };
                 (token::Str, symbol, None)
             }
             LitKind::Str(symbol, ast::StrStyle::Raw(n)) => {

Diff for: src/libsyntax/parse/parser/module.rs

@@ -229,7 +229,7 @@ impl<'a> Parser<'a> {
         // `./<id>.rs` and `./<id>/mod.rs`.
         let relative_prefix_string;
         let relative_prefix = if let Some(ident) = relative {
-            relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
+            relative_prefix_string = format!("{}{}", ident, path::MAIN_SEPARATOR);
             &relative_prefix_string
         } else {
             ""

Diff for: src/libsyntax_ext/env.rs

@@ -21,7 +21,7 @@ pub fn expand_option_env<'cx>(cx: &'cx mut ExtCtxt<'_>,
     };
 
     let sp = cx.with_def_site_ctxt(sp);
-    let e = match env::var(&*var.as_str()) {
+    let e = match env::var(&var.as_str()) {
         Err(..) => {
             let lt = cx.lifetime(sp, Ident::new(kw::StaticLifetime, sp));
             cx.expr_path(cx.path_all(sp,

Diff for: src/libsyntax_ext/format.rs

@@ -992,7 +992,7 @@ pub fn expand_preparsed_format_args(
         vec![]
     };
 
-    let fmt_str = &*fmt_str.as_str();  // for the suggestions below
+    let fmt_str = &fmt_str.as_str();  // for the suggestions below
     let mut parser = parse::Parser::new(fmt_str, str_style, skips, append_newline);
 
     let mut unverified_pieces = Vec::new();