is_dataclass() does not work for dataclasses which are subclasses of types.GenericAlias

[serhiy-storchaka]

BPO	45663
Nosy	@gvanrossum, @ericvsmith, @serhiy-storchaka, @miss-islington
PRs	bpo-45663: Fix is_dataclass() for dataclasses which are subclasses of types.GenericAlias #29294 [3.10] bpo-45663: Fix is_dataclass() for dataclasses which are subclasses of types.GenericAlias (GH-29294) #29925 [3.9] bpo-45663: Fix is_dataclass() for dataclasses which are subclasses of types.GenericAlias (GH-29294) #29926

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

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GitHub fields:

assignee = None
closed_at = <Date 2021-12-07.12:01:12.403>
created_at = <Date 2021-10-28.20:10:31.152>
labels = ['type-bug', 'library', '3.9', '3.10', '3.11']
title = 'is_dataclass() does not work for dataclasses which are subclasses of types.GenericAlias'
updated_at = <Date 2021-12-07.12:01:12.402>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2021-12-07.12:01:12.402>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2021-12-07.12:01:12.403>
closer = 'serhiy.storchaka'
components = ['Library (Lib)']
creation = <Date 2021-10-28.20:10:31.152>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 45663
keywords = ['patch']
message_count = 4.0
messages = ['405256', '407739', '407743', '407745']
nosy_count = 4.0
nosy_names = ['gvanrossum', 'eric.smith', 'serhiy.storchaka', 'miss-islington']
pr_nums = ['29294', '29925', '29926']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45663'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

[serhiy-storchaka]

>>> import dataclasses, types
>>> @dataclasses.dataclass
... class A(types.GenericAlias):
...     origin: type
...     args: type
... 
>>> dataclasses.is_dataclass(A)
True
>>> a = A(list, int)
>>> dataclasses.is_dataclass(type(a))
True
>>> dataclasses.is_dataclass(a)
False

[serhiy-storchaka]

New changeset 446be16 by Serhiy Storchaka in branch 'main':
bpo-45663: Fix is_dataclass() for dataclasses which are subclasses of types.GenericAlias (GH-29294)
446be16

[miss-islington]

New changeset abceb66 by Miss Islington (bot) in branch '3.10':
bpo-45663: Fix is_dataclass() for dataclasses which are subclasses of types.GenericAlias (GH-29294)
abceb66

[miss-islington]

New changeset 1905071 by Miss Islington (bot) in branch '3.9':
bpo-45663: Fix is_dataclass() for dataclasses which are subclasses of types.GenericAlias (GH-29294)
1905071