From ec9c949946ef805ec5d70b87a15504c62361153d Mon Sep 17 00:00:00 2001
From: bjorn3 <bjorn3@users.noreply.github.com>
Date: Mon, 10 Jan 2022 17:08:21 +0100
Subject: [PATCH] Use pre-interned symbols in a couple of places

---
 compiler/rustc_ast_lowering/src/expr.rs            | 14 ++++++++------
 .../src/infer/error_reporting/need_type_info.rs    |  8 ++++----
 compiler/rustc_span/src/symbol.rs                  |  3 +++
 compiler/rustc_typeck/src/check/method/suggest.rs  |  5 ++---
 4 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 75f384405bb2b..885537a212fe1 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -11,7 +11,7 @@ use rustc_hir::def::Res;
 use rustc_hir::definitions::DefPathData;
 use rustc_span::hygiene::ExpnId;
 use rustc_span::source_map::{respan, DesugaringKind, Span, Spanned};
-use rustc_span::symbol::{sym, Ident, Symbol};
+use rustc_span::symbol::{sym, Ident};
 use rustc_span::DUMMY_SP;
 
 impl<'hir> LoweringContext<'_, 'hir> {
@@ -1204,11 +1204,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
         };
 
         let fields = self.arena.alloc_from_iter(
-            e1.iter().map(|e| ("start", e)).chain(e2.iter().map(|e| ("end", e))).map(|(s, e)| {
-                let expr = self.lower_expr(&e);
-                let ident = Ident::new(Symbol::intern(s), self.lower_span(e.span));
-                self.expr_field(ident, expr, e.span)
-            }),
+            e1.iter().map(|e| (sym::start, e)).chain(e2.iter().map(|e| (sym::end, e))).map(
+                |(s, e)| {
+                    let expr = self.lower_expr(&e);
+                    let ident = Ident::new(s, self.lower_span(e.span));
+                    self.expr_field(ident, expr, e.span)
+                },
+            ),
         );
 
         hir::ExprKind::Struct(
diff --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
index 9cf6cde259150..e5210c5b19063 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
@@ -12,7 +12,7 @@ use rustc_middle::ty::print::Print;
 use rustc_middle::ty::subst::{GenericArg, GenericArgKind};
 use rustc_middle::ty::{self, Const, DefIdTree, InferConst, Ty, TyCtxt, TypeFoldable, TypeFolder};
 use rustc_span::symbol::kw;
-use rustc_span::Span;
+use rustc_span::{sym, Span};
 use std::borrow::Cow;
 
 struct FindHirNodeVisitor<'a, 'tcx> {
@@ -1003,9 +1003,9 @@ impl<'tcx> TypeFolder<'tcx> for ResolvedTypeParamEraser<'tcx> {
             | ty::Opaque(..)
             | ty::Projection(_)
             | ty::Never => t.super_fold_with(self),
-            ty::Array(ty, c) => self
-                .tcx()
-                .mk_ty(ty::Array(self.fold_ty(ty), self.replace_infers(c, 0, Symbol::intern("N")))),
+            ty::Array(ty, c) => {
+                self.tcx().mk_ty(ty::Array(self.fold_ty(ty), self.replace_infers(c, 0, sym::N)))
+            }
             // We don't want to hide type params that haven't been resolved yet.
             // This would be the type that will be written out with the type param
             // name in the output.
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 84cf8878af809..478dda2009c00 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -208,6 +208,7 @@ symbols! {
         LinkedList,
         LintPass,
         Mutex,
+        N,
         None,
         Ok,
         Option,
@@ -327,6 +328,7 @@ symbols! {
         array,
         arrays,
         as_ptr,
+        as_ref,
         as_str,
         asm,
         asm_const,
@@ -592,6 +594,7 @@ symbols! {
         enable,
         enclosing_scope,
         encode,
+        end,
         env,
         eq,
         ermsb_target_feature,
diff --git a/compiler/rustc_typeck/src/check/method/suggest.rs b/compiler/rustc_typeck/src/check/method/suggest.rs
index 1a6fcbc57bff2..fdf440f955c63 100644
--- a/compiler/rustc_typeck/src/check/method/suggest.rs
+++ b/compiler/rustc_typeck/src/check/method/suggest.rs
@@ -15,7 +15,7 @@ use rustc_middle::ty::print::with_crate_prefix;
 use rustc_middle::ty::{self, DefIdTree, ToPredicate, Ty, TyCtxt, TypeFoldable};
 use rustc_span::lev_distance;
 use rustc_span::symbol::{kw, sym, Ident};
-use rustc_span::{source_map, FileName, MultiSpan, Span, Symbol};
+use rustc_span::{source_map, FileName, MultiSpan, Span};
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 use rustc_trait_selection::traits::{
     FulfillmentError, Obligation, ObligationCause, ObligationCauseCode,
@@ -1524,8 +1524,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             // Explicitly ignore the `Pin::as_ref()` method as `Pin` does not
                             // implement the `AsRef` trait.
                             let skip = skippable.contains(&did)
-                                || (("Pin::new" == *pre)
-                                    && (Symbol::intern("as_ref") == item_name.name));
+                                || (("Pin::new" == *pre) && (sym::as_ref == item_name.name));
                             // Make sure the method is defined for the *actual* receiver: we don't
                             // want to treat `Box<Self>` as a receiver if it only works because of
                             // an autoderef to `&self`