Dataclass classmethods don't work

[catern]

On master and 0.630, the following code fails with error: Incompatible return value type (got "Foo", expected "T"):

from dataclasses import dataclass
import typing as t

T = t.TypeVar('T', bound="Foo")
@dataclass
class Foo:
    @classmethod
    def make(cls: t.Type[T]) -> T:
        return cls()

If I remove the dataclass annotation, it works fine.

[JelleZijlstra]

cc @euresti since this seems to be due to the dataclasses plugin.

[euresti]

Hmm. In my code I usually annotate this as:

@dataclass
class Foo:
    @classmethod
    def make(cls) -> 'Foo':
        return cls()

But I hardly use inheritance.

Also I don't know why the decorator would break it. Does it happens with @attr.s?

[ilevkivskyi]

This works on master

[ilevkivskyi]

Also this is a duplicate of #5263 that was fixed by #5646