bpo-42740: Fix get_args for PEP 585 collections.abc.Callable (GH-23963)

PR 1/2. Needs backport to 3.9.

2 files changed, 6 insertions, 3 deletions

diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index c340c8a..3dcc31f 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -3048,6 +3048,11 @@ class GetUtilitiesTestCase(TestCase):
         self.assertEqual(get_args(Callable), ())
         self.assertEqual(get_args(list[int]), (int,))
         self.assertEqual(get_args(list), ())
+        self.assertEqual(get_args(collections.abc.Callable[[int], str]), ([int], str))
+        self.assertEqual(get_args(collections.abc.Callable[..., str]), (..., str))
+        self.assertEqual(get_args(collections.abc.Callable[[], str]), ([], str))
+        self.assertEqual(get_args(collections.abc.Callable[[int], str]),
+                         get_args(Callable[[int], str]))
 
 
 class CollectionsAbcTests(BaseTestCase):
diff --git a/Lib/typing.py b/Lib/typing.py
index 7b79876..67e95dd 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -1684,13 +1684,11 @@ def get_args(tp):
     """
     if isinstance(tp, _AnnotatedAlias):
         return (tp.__origin__,) + tp.__metadata__
-    if isinstance(tp, _GenericAlias):
+    if isinstance(tp, (_GenericAlias, GenericAlias)):
         res = tp.__args__
         if tp.__origin__ is collections.abc.Callable and res[0] is not Ellipsis:
             res = (list(res[:-1]), res[-1])
         return res
-    if isinstance(tp, GenericAlias):
-        return tp.__args__
     return ()