From bd33b4972da88f55dbeaca8be43350e35021d2ea Mon Sep 17 00:00:00 2001
From: Micha Reiser <micha@reiser.io>
Date: Sat, 19 Oct 2024 13:07:15 +0200
Subject: [PATCH] Short circuit `lex_identifier` if the name is longer or
 shorter than any known keyword (#13815)

---
 crates/ruff_python_parser/src/lexer.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/crates/ruff_python_parser/src/lexer.rs b/crates/ruff_python_parser/src/lexer.rs
index d407ab357e..4bc4bb4319 100644
--- a/crates/ruff_python_parser/src/lexer.rs
+++ b/crates/ruff_python_parser/src/lexer.rs
@@ -648,6 +648,14 @@ impl<'src> Lexer<'src> {
             return TokenKind::Name;
         }
 
+        // Short circuit for names that are longer than any known keyword.
+        // It helps Rust to predict that the Name::new call in the keyword match's default branch
+        // is guaranteed to fit into a stack allocated (inline) Name.
+        if text.len() > 8 {
+            self.current_value = TokenValue::Name(Name::new(text));
+            return TokenKind::Name;
+        }
+
         match text {
             "False" => TokenKind::False,
             "None" => TokenKind::None,