ClassVar[TypeAlias] in dataclass-like classes becomes Any

Bug Report

When defining a type alias within a dataclass (or attrs) class, it has to be marked as ClassVar[^1] which causes the field to be treated as Any.

This bug has been already reported in https://github.com/python/mypy/issues/9238#issuecomment-1089065588 but never followed up.

To Reproduce

from dataclasses import dataclass
from typing import ClassVar, TypeAlias


@dataclass
class Namespace:
    Alias: ClassVar[TypeAlias] = int
    
reveal_type(Namespace.Alias)

https://mypy-play.net/?mypy=latest&python=3.12&gist=e66e903f3b055fa8433707a5e8b99ebc

Expected Behavior

main.py:16: note: Revealed type is "int"

Actual Behavior

main.py:16: note: Revealed type is "Any"

Your Environment

See the playground. Python 3.12 on Mypy 1.9.0.

[^1]: The attrs plugin crashes with an assertion error if this is forgotten, but that's a bug for another day.

Commencez par exécuter le reproducteur Python fourni avec mypy 1.9.0 et comparez le type révélé avec le int attendu. Suivez la manière dont ClassVar[TypeAlias] est traité dans les classes de type dataclass, puis ajoutez ou mettez à jour la couverture afin que le type révélé ne soit plus Any ; l’assertion de attrs-plugin est explicitement hors périmètre.