gh-155278: Avoid needlessly accessing `ForwardRef.__forward_code__` in `evaluate_forward_ref()` (#155279)

https://github.com/python/cpython/commit/5ffefdb108094a44e84345561ab1f1b57ffda23f
commit: 5ffefdb108094a44e84345561ab1f1b57ffda23f
branch: main
author: Victorien <[email protected]>
committer: JelleZijlstra <[email protected]>
date: 2026-08-07T15:16:25-07:00
summary:

gh-155278: Avoid needlessly accessing `ForwardRef.__forward_code__` in `evaluate_forward_ref()` (#155279)

files:
M Lib/typing.py

diff --git a/Lib/typing.py b/Lib/typing.py
index b56ba954ad38be..65e1d1ea6be584 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -25,6 +25,7 @@
 import collections.abc
 import copyreg
 import functools
+import keyword
 import operator
 import sys
 import types
@@ -998,8 +999,12 @@ def _make_forward_ref(code, *, parent_fwdref=None, **kwargs):
         if parent_fwdref.__owner__ is not None:
             kwargs['owner'] = parent_fwdref.__owner__
     forward_ref = annotationlib.ForwardRef(code, **kwargs)
-    # For compatibility, eagerly compile the forwardref's code.
-    forward_ref.__forward_code__
+    # For compatibility, eagerly compile the forwardref's code so that any
+    # SyntaxError is raised immediately rather than when the forward
+    # reference is evaluated. Similar to 'ForwardRef.evaluate()', we only compile
+    # it if necessary:
+    if not (code.isidentifier() and not keyword.iskeyword(code)):
+        forward_ref.__forward_code__
     return forward_ref
 
 

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