Fix not using type_params in < 3.12.5

Author: Daraan

src/test_typing_extensions.py

@@ -8947,14 +8947,11 @@ class Y(Generic[Tx]):
         self.assertEqual(get_origin(evaluated_ref1a), Y)
         self.assertEqual(get_args(evaluated_ref1a), (Y[Tx],))
 
-        with self.subTest("nested string with type_params"):
-            if not TYPING_3_12_0:
-                self.skipTest("# TODO find reason why this one fails before 3.12.?")
-            evaluated_ref1b = evaluate_forward_ref(
-                typing.ForwardRef("Y[Y['Tx']]"), locals={"Y": Y}, type_params=(Tx,)
-            )
-            self.assertEqual(get_origin(evaluated_ref1b), Y)
-            self.assertEqual(get_args(evaluated_ref1b), (Y[Tx],))
+        evaluated_ref1b = evaluate_forward_ref(
+            typing.ForwardRef("Y[Y['Tx']]"), locals={"Y": Y}, type_params=(Tx,)
+        )
+        self.assertEqual(get_origin(evaluated_ref1b), Y)
+        self.assertEqual(get_args(evaluated_ref1b), (Y[Tx],))
 
         with self.subTest("nested string of TypeVar"):
             evaluated_ref2 = evaluate_forward_ref(typing.ForwardRef("""Y["Y['Tx']"]"""), locals={"Y": Y})

src/typing_extensions.py

@@ -4357,6 +4357,12 @@ def evaluate_forward_ref(
                  type_params=type_params, owner=owner,
                 _recursive_guard=_recursive_guard, format=format
             )
+        if sys.version_info < (3, 12, 5) and type_params:
+            # Make use of type_params
+            locals = dict(locals) if locals else {}
+            for tvar in type_params:
+                if tvar.__name__ not in locals:  # lets not overwrite something present
+                    locals[tvar.__name__] = tvar
         if sys.version_info < (3, 9):
             return typing._eval_type(
                 type_,