Auto merge of #60910 - nnethercote:avoid-some-unnecessary-interning, r=petrochenkov

Avoid some unnecessary interning

r? @petrochenkov

src/librustc/hir/lowering.rs

@@ -2218,7 +2218,7 @@ impl<'a> LoweringContext<'a> {
                         bindings: hir_vec![
                             hir::TypeBinding {
                                 hir_id: this.next_id(),
-                                ident: Ident::from_str(FN_OUTPUT_NAME),
+                                ident: Ident::with_empty_ctxt(FN_OUTPUT_NAME),
                                 ty: output
                                     .as_ref()
                                     .map(|ty| this.lower_ty(&ty, ImplTraitContext::disallowed()))
@@ -2543,7 +2543,7 @@ impl<'a> LoweringContext<'a> {
         let future_params = P(hir::GenericArgs {
             args: hir_vec![],
             bindings: hir_vec![hir::TypeBinding {
-                ident: Ident::from_str(FN_OUTPUT_NAME),
+                ident: Ident::with_empty_ctxt(FN_OUTPUT_NAME),
                 ty: output_ty,
                 hir_id: self.next_id(),
                 span,
@@ -4801,7 +4801,7 @@ impl<'a> LoweringContext<'a> {
                 let attr = {
                     // `allow(unreachable_code)`
                     let allow = {
-                        let allow_ident = Ident::from_str("allow").with_span_pos(e.span);
+                        let allow_ident = Ident::with_empty_ctxt(sym::allow).with_span_pos(e.span);
                         let uc_ident = Ident::from_str("unreachable_code").with_span_pos(e.span);
                         let uc_nested = attr::mk_nested_word_item(uc_ident);
                         attr::mk_list_item(e.span, allow_ident, vec![uc_nested])

src/librustc/hir/map/definitions.rs

@@ -17,7 +17,7 @@ use std::fmt::Write;
 use std::hash::Hash;
 use syntax::ast;
 use syntax::ext::hygiene::Mark;
-use syntax::symbol::{Symbol, InternedString};
+use syntax::symbol::{Symbol, sym, InternedString};
 use syntax_pos::{Span, DUMMY_SP};
 use crate::util::nodemap::NodeMap;
 
@@ -584,16 +584,16 @@ impl DefPathData {
                 return name
             }
             // note that this does not show up in user printouts
-            CrateRoot => "{{crate}}",
-            Impl => "{{impl}}",
-            Misc => "{{misc}}",
-            ClosureExpr => "{{closure}}",
-            Ctor => "{{constructor}}",
-            AnonConst => "{{constant}}",
-            ImplTrait => "{{opaque}}",
+            CrateRoot => sym::double_braced_crate,
+            Impl => sym::double_braced_impl,
+            Misc => sym::double_braced_misc,
+            ClosureExpr => sym::double_braced_closure,
+            Ctor => sym::double_braced_constructor,
+            AnonConst => sym::double_braced_constant,
+            ImplTrait => sym::double_braced_opaque,
         };
 
-        Symbol::intern(s).as_interned_str()
+        s.as_interned_str()
     }
 
     pub fn to_string(&self) -> String {

src/librustc/traits/project.rs

@@ -1421,7 +1421,7 @@ fn confirm_callable_candidate<'cx, 'gcx, 'tcx>(
                 projection_ty: ty::ProjectionTy::from_ref_and_name(
                     tcx,
                     trait_ref,
-                    Ident::from_str(FN_OUTPUT_NAME),
+                    Ident::with_empty_ctxt(FN_OUTPUT_NAME),
                 ),
                 ty: ret_type
             }

src/librustc/util/common.rs

@@ -11,6 +11,7 @@ use std::time::{Duration, Instant};
 
 use std::sync::mpsc::{Sender};
 use syntax_pos::{SpanData};
+use syntax::symbol::{Symbol, sym};
 use rustc_macros::HashStable;
 use crate::ty::TyCtxt;
 use crate::dep_graph::{DepNode};
@@ -18,7 +19,7 @@ use lazy_static;
 use crate::session::Session;
 
 // The name of the associated type for `Fn` return types
-pub const FN_OUTPUT_NAME: &str = "Output";
+pub const FN_OUTPUT_NAME: Symbol = sym::Output;
 
 // Useful type to use with `Result<>` indicate that an error has already
 // been reported to the user, so no need to continue checking.