bpo-40398: Fix typing.get_args() for special generic aliases. (GH-19720)

diff --git a/Lib/typing.py b/Lib/typing.py
index 1aefcb8..c829898 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -1420,11 +1420,13 @@
     """
     if isinstance(tp, _AnnotatedAlias):
         return (tp.__origin__,) + tp.__metadata__
-    if isinstance(tp, (_GenericAlias, GenericAlias)):
+    if isinstance(tp, _GenericAlias) and not tp._special:
         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 ()