Optimize check_keyword_case.

`to_lowercase` allocates, but `eq_ignore_ascii_case` doesn't. This path is hot enough that this makes a small but noticeable difference in benchmarking.
rust-lang · Nov 12, 2024 · 99d02fb · 99d02fb
1 parent f7273e0
commit 99d02fb
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
@@ -641,9 +641,10 @@ impl<'a> Parser<'a> {
             return true;
         }
 
+        // Do an ASCII case-insensitive match, because all keywords are ASCII.
         if case == Case::Insensitive
             && let Some((ident, IdentIsRaw::No)) = self.token.ident()
-            && ident.as_str().to_lowercase() == kw.as_str().to_lowercase()
+            && ident.as_str().eq_ignore_ascii_case(kw.as_str())
         {
             true
         } else {