Auto merge of #135371 - Mark-Simulacrum:no-alloc-case-cmp, r=compiler-errors

Remove allocations from case-insensitive comparison to keywords

Follows up on work in 99d02fb40fd339255ed08596ebeb41e9b8a09d45, expanding the alloc-free comparisons to more cases of case-insensitive keyword matching.

r? ghost for perf

1 files changed, 3 insertions, 2 deletions

diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 2637ea268c8..10756be6afb 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -655,9 +655,9 @@ impl<'a> Parser<'a> {
     fn check_keyword_case(&mut self, exp: ExpKeywordPair, case: Case) -> bool {
         if self.check_keyword(exp) {
             true
-        // Do an ASCII case-insensitive match, because all keywords are ASCII.
         } else if case == Case::Insensitive
             && let Some((ident, IdentIsRaw::No)) = self.token.ident()
+            // Do an ASCII case-insensitive match, because all keywords are ASCII.
             && ident.as_str().eq_ignore_ascii_case(exp.kw.as_str())
         {
             true
@@ -689,7 +689,8 @@ impl<'a> Parser<'a> {
             true
         } else if case == Case::Insensitive
             && let Some((ident, IdentIsRaw::No)) = self.token.ident()
-            && ident.as_str().to_lowercase() == exp.kw.as_str().to_lowercase()
+            // Do an ASCII case-insensitive match, because all keywords are ASCII.
+            && ident.as_str().eq_ignore_ascii_case(exp.kw.as_str())
         {
             self.dcx().emit_err(errors::KwBadCase { span: ident.span, kw: exp.kw.as_str() });
             self.bump();