gh-138151: Fix ForwardRef.evaluate() for locally defined generics

Lib/annotationlib.py

@@ -167,6 +167,13 @@ def evaluate(
                 globals[param.__name__] = param
         if self.__extra_names__:
             locals = {**locals, **self.__extra_names__}
+        if (annotate := getattr(owner, "__annotate__", None)) and annotate.__closure__:
+            for name, cell in zip(annotate.__code__.co_freevars, annotate.__closure__):
+                if name != "__classdict__":
+                    try:
+                        locals[name] = cell.cell_contents
+                    except ValueError:
+                        pass
 
         arg = self.__forward_arg__
         if arg.isidentifier() and not keyword.iskeyword(arg):

Lib/test/test_annotationlib.py

@@ -1617,6 +1617,33 @@ def test_evaluate_with_type_params_and_scope_conflict(self):
                     TypeParamsSample.TypeParamsAlias2,
                 )
 
+    def test_evaluate_local_generic(self):
+        class Cls:
+            nonlocal alias, alias2, alias3
+            x: alias[int]
+            y: alias[alias]
+            z: alias[alias2, alias3]
+
+        fwdref = get_annotations(Cls, format=Format.FORWARDREF)["x"]
+        with self.assertRaises(NameError):
+            fwdref.evaluate()
+
+        alias = list
+        self.assertEqual(fwdref.evaluate(), list[int])
+
+        del alias
+        fwdref = get_annotations(Cls, format=Format.FORWARDREF)["y"]
+        alias = list
+        self.assertEqual(fwdref.evaluate(), list[list])
+
+        del alias
+        fwdref = get_annotations(Cls, format=Format.FORWARDREF)["z"]
+        alias = dict
+        alias2 = int
+        alias3 = str
+        self.assertEqual(fwdref.evaluate(), dict[int, str])
+
+
     def test_fwdref_with_module(self):
         self.assertIs(ForwardRef("Format", module="annotationlib").evaluate(), Format)
         self.assertIs(

Misc/NEWS.d/next/Library/2025-08-27-12-06-52.gh-issue-138151.ajQpH5.rst

@@ -0,0 +1,2 @@
+Fix :meth:`annotationlib.ForwardRef.evaluate` not handling generics with
+nonlocal variables that are defined after the annotation.