From 18e33cb742ce637a25dfac224683273f88d05363 Mon Sep 17 00:00:00 2001
From: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
Date: Sat, 2 Jan 2021 18:05:32 +0800
Subject: [PATCH] raise typeerror when passing subclasses of genericaliases
 into isinstance/issubclass

---
 Lib/test/test_types.py | 10 ++++++++++
 Objects/unionobject.c  |  2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index 83196ad3c17436..d8a48ce36f618c 100644
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -737,6 +737,16 @@ def __eq__(self, other):
         with self.assertRaises(ZeroDivisionError):
             list[int] | list[bt]
 
+        union_ga = (int | list[str], int | collections.abc.Callable[..., str],
+                    int | d)
+        # Raise error when isinstance(type, type | genericalias)
+        for type_ in union_ga:
+            with self.subTest(f"check isinstance/issubclass is invalid for {type_}"):
+                with self.assertRaises(TypeError):
+                    isinstance(list, type_)
+                with self.assertRaises(TypeError):
+                    issubclass(list, type_)
+
     def test_ellipsis_type(self):
         self.assertIsInstance(Ellipsis, types.EllipsisType)
 
diff --git a/Objects/unionobject.c b/Objects/unionobject.c
index 32aa5078afcef4..05350363eed63f 100644
--- a/Objects/unionobject.c
+++ b/Objects/unionobject.c
@@ -34,7 +34,7 @@ is_generic_alias_in_args(PyObject *args) {
     Py_ssize_t nargs = PyTuple_GET_SIZE(args);
     for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
         PyObject *arg = PyTuple_GET_ITEM(args, iarg);
-        if (Py_TYPE(arg) == &Py_GenericAliasType) {
+        if (PyObject_TypeCheck(arg, &Py_GenericAliasType)) {
             return 0;
         }
     }