[Python-checkins] bpo-45664: Fix resolve_bases() and new_class() for GenericAlias instance as a base (GH-29298)

[serhiy-storchaka]

https://github.com/python/cpython/commit/2b318ce1c988b7b6e3caf293d55f289e066b6e0f
commit: 2b318ce1c988b7b6e3caf293d55f289e066b6e0f
branch: main
author: Serhiy Storchaka <storchaka at gmail.com>
committer: serhiy-storchaka <storchaka at gmail.com>
date: 2021-12-05T22:44:01+02:00
summary:

bpo-45664: Fix resolve_bases() and new_class() for GenericAlias instance as a base (GH-29298)

files:
A Misc/NEWS.d/next/Library/2021-10-28-23-40-54.bpo-45664.7dqtxQ.rst
M Lib/test/test_types.py
M Lib/types.py

diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index b1218abc8af5e..3dfda5cb95663 100644
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -1236,6 +1236,17 @@ def __mro_entries__(self, bases):
         self.assertEqual(D.__orig_bases__, (c,))
         self.assertEqual(D.__mro__, (D, A, object))
 
+    def test_new_class_with_mro_entry_genericalias(self):
+        L1 = types.new_class('L1', (typing.List[int],), {})
+        self.assertEqual(L1.__bases__, (list, typing.Generic))
+        self.assertEqual(L1.__orig_bases__, (typing.List[int],))
+        self.assertEqual(L1.__mro__, (L1, list, typing.Generic, object))
+
+        L2 = types.new_class('L2', (list[int],), {})
+        self.assertEqual(L2.__bases__, (list,))
+        self.assertEqual(L2.__orig_bases__, (list[int],))
+        self.assertEqual(L2.__mro__, (L2, list, object))
+
     def test_new_class_with_mro_entry_none(self):
         class A: pass
         class B: pass
@@ -1351,6 +1362,11 @@ def __mro_entries__(self, bases):
         for bases in [x, y, z, t]:
             self.assertIs(types.resolve_bases(bases), bases)
 
+    def test_resolve_bases_with_mro_entry(self):
+        self.assertEqual(types.resolve_bases((typing.List[int],)),
+                         (list, typing.Generic))
+        self.assertEqual(types.resolve_bases((list[int],)), (list,))
+
     def test_metaclass_derivation(self):
         # issue1294232: correct metaclass calculation
         new_calls = []  # to check the order of __new__ calls
diff --git a/Lib/types.py b/Lib/types.py
index ce1c28d5625a2..679c7f638b310 100644
--- a/Lib/types.py
+++ b/Lib/types.py
@@ -82,7 +82,7 @@ def resolve_bases(bases):
     updated = False
     shift = 0
     for i, base in enumerate(bases):
-        if isinstance(base, type):
+        if isinstance(base, type) and not isinstance(base, GenericAlias):
             continue
         if not hasattr(base, "__mro_entries__"):
             continue
diff --git a/Misc/NEWS.d/next/Library/2021-10-28-23-40-54.bpo-45664.7dqtxQ.rst b/Misc/NEWS.d/next/Library/2021-10-28-23-40-54.bpo-45664.7dqtxQ.rst
new file mode 100644
index 0000000000000..573a569845a87
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-10-28-23-40-54.bpo-45664.7dqtxQ.rst
@@ -0,0 +1,2 @@
+Fix :func:`types.resolve_bases` and :func:`types.new_class` for
+:class:`types.GenericAlias` instance as a base.