bpo-42904: Fix get_type_hints for class local namespaces (GH-24201)

Author: Fidget-Spinner

Lib/test/test_typing.py

@@ -2874,7 +2874,7 @@ def test_get_type_hints_classes(self):
                          {'x': int, 'y': int})
         self.assertEqual(gth(mod_generics_cache.B),
                          {'my_inner_a1': mod_generics_cache.B.A,
-                          'my_inner_a2': mod_generics_cache.A,
+                          'my_inner_a2': mod_generics_cache.B.A,
                           'my_outer_a': mod_generics_cache.A})
 
     def test_respect_no_type_check(self):
@@ -3010,6 +3010,13 @@ def __iand__(self, other: Const["MySet[T]"]) -> "MySet[T]":
             {'other': MySet[T], 'return': MySet[T]}
         )
 
+    def test_get_type_hints_classes(self):
+        class Foo:
+            y = str
+            x: y
+        # This previously raised an error under PEP 563.
+        self.assertEqual(get_type_hints(Foo), {'x': str})
+
 
 class GetUtilitiesTestCase(TestCase):
     def test_get_origin(self):

Lib/typing.py

@@ -1632,12 +1632,13 @@ def get_type_hints(obj, globalns=None, localns=None, include_extras=False):
             else:
                 base_globals = globalns
             ann = base.__dict__.get('__annotations__', {})
+            base_locals = dict(vars(base)) if localns is None else localns
             for name, value in ann.items():
                 if value is None:
                     value = type(None)
                 if isinstance(value, str):
                     value = ForwardRef(value, is_argument=False)
-                value = _eval_type(value, base_globals, localns)
+                value = _eval_type(value, base_globals, base_locals)
                 hints[name] = value
         return hints if include_extras else {k: _strip_annotations(t) for k, t in hints.items()}
 

Misc/NEWS.d/next/Library/2021-01-12-23-17-02.bpo-42904.-4qkTD.rst

@@ -0,0 +1,2 @@
+:func:`typing.get_type_hints` now checks the local namespace of a class when
+evaluating :pep:`563` annotations inside said class.