Attrs plugin mishandles typing.Self in generated inits

[FasterSpeeding]

Bug Report

MyPy mishandles type comparisons when an argument in an attrs generated init uses typing.Self.

To Reproduce

import attrs
import typing

from typing_extensions import Self


@attrs.define()
class Dataclass:
    child: typing.Optional[Self] = None


Dataclass(child=Dataclass())

Expected Behavior

The attrs version of this code should pass type checking like MyPy does with the following dataclasses and normal init examples

import typing

import dataclasses
from typing_extensions import Self


@dataclasses.dataclass
class Dataclass:
    child: typing.Optional[Self] = None


Dataclass(child=Dataclass())

import typing

from typing_extensions import Self


class Dataclass:
    def __init__(self, child: typing.Optional[Self] = None) -> None:
        self.child = child
    

Dataclass(child=Dataclass())

Actual Behavior

MyPy false-positive reports an incompatible type for the argument only when using attrs

test.py:12: error: Argument "child" to "Dataclass" has incompatible type "Dataclass"; expected "Optional[Self]"  [arg-type]
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 1.0.0
• Mypy command-line flags: --strict
• Mypy configuration options from mypy.ini (and other config files):
• Python version used: 3.10.9
• Attrs version used: 22.2.0

[PhilReinhold]

I think this is related to the similar problem I was experiencing:

from typing_extensions import Self

class A:
    def __init__(self) -> None:
        self.related: list[Self] = []

    def copy(self) -> Self:
        raise NotImplementedError

    def add_related(self) -> None:
        self.related.append(self.copy())

which when ran through mypy 1.0.0 gives

test.py:11: error: Argument 1 to "append" of "list" has incompatible type "A"; expected "Self"  [arg-type]

[davfsa]

I think this is related to the similar problem I was experiencing:

@PhilReinhold nope, that seems to be similar to #14685, which I have opened a pr (#14712) to try and fix