resolve_bases() and new_class() do not work with type alias of a built-in type

[serhiy-storchaka]

BPO	45664
Nosy	@gvanrossum, @serhiy-storchaka, @1st1, @miss-islington, @Fidget-Spinner
PRs	bpo-45664: Fix resolve_bases() and new_class() for GenericAlias instance as a base #29298 [3.10] bpo-45664: Fix resolve_bases() and new_class() for GenericAlias instance as a base (GH-29298) #29927 [3.9] bpo-45664: Fix resolve_bases() and new_class() for GenericAlias instance as a base (GH-29298) #29928

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2021-12-07.12:00:37.234>
created_at = <Date 2021-10-28.20:38:27.785>
labels = ['type-bug', 'library', '3.9', '3.10', '3.11']
title = 'resolve_bases() and new_class() do not work with type alias of a built-in type'
updated_at = <Date 2021-12-07.12:00:37.234>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2021-12-07.12:00:37.234>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2021-12-07.12:00:37.234>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2021-10-28.20:38:27.785>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 45664
keywords = ['patch']
message_count = 4.0
messages = ['405265', '407740', '407746', '407926']
nosy_count = 5.0
nosy_names = ['gvanrossum', 'serhiy.storchaka', 'yselivanov', 'miss-islington', 'kj']
pr_nums = ['29298', '29927', '29928']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45664'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

[serhiy-storchaka]

resolve_bases() returns incorrect result:

>>> import types
>>> types.resolve_bases((list[int],))
(list[int],)

Expected (list,).

new_class() fails:

>>> types.new_class('L', (list[int],),{})
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "/home/serhiy/py/cpython/Lib/types.py", line 77, in new_class
 return meta(name, resolved_bases, ns, **kwds)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: GenericAlias expected 2 arguments, got 3

Both work well with typing.List[int].

[serhiy-storchaka]

New changeset 2b318ce by Serhiy Storchaka in branch 'main':
bpo-45664: Fix resolve_bases() and new_class() for GenericAlias instance as a base (GH-29298)
2b318ce

[miss-islington]

New changeset cb68c0a by Miss Islington (bot) in branch '3.10':
bpo-45664: Fix resolve_bases() and new_class() for GenericAlias instance as a base (GH-29298)
cb68c0a

[serhiy-storchaka]

New changeset bffce2c by Miss Islington (bot) in branch '3.9':
bpo-45664: Fix resolve_bases() and new_class() for GenericAlias instance as a base (GH-29298) (GH-29928)
bffce2c