Unexpected overload match for generic class

[chdsbd]

Bug Report

For a generic class with __init__ overloads and __get__ overloads, mypy is matching overloads unexpectedly.

To Reproduce

1. Run the playground: https://mypy-play.net/?mypy=latest&python=3.9&gist=a0ad74a30c7089c1aa0d9446e635ce93
2. Observe the types of audience.usernames and audience.ages are both list[int]

Here's the example code from the playground:

from __future__ import annotations
from typing import Any, Generic, TypeVar, overload, List
from typing_extensions import Literal


_T = TypeVar("_T")


class ListField(Generic[_T]):
    @overload
    def __init__(
        self: ListField[int],
        *,
        kind: Literal["integer"],
    ) -> None:
        ...

    @overload
    def __init__(
        self: ListField[str],
        *,
        kind: Literal["string"],
    ) -> None:
        ...

    def __init__(self, *, kind: Any) -> None:
        ...

    @overload
    def __get__(
        self: ListField[int],
        instance: Any,
        owner: Any,
    ) -> List[int]:
        ...

    @overload
    def __get__(
        self: ListField[str],
        instance: Any,
        owner: Any,
    ) -> List[str]:
        ...

    def __get__(self: Any, instance: Any, owner: Any) -> Any:
        ...


class Audience:
    usernames = ListField(kind="string")
    ages = ListField(kind="integer")


audience = Audience()
reveal_type(audience.usernames)  # Revealed type is list[int]
reveal_type(audience.ages)  # Revealed type is list[int]

Expected Behavior

I would expect audience.usernames to be a list[str], because the __init__ overload should create a ListField[str], which should then match to __get__ overload for ListField[str], returning list[str].

Actual Behavior

audience.usernames is unexpectedly typed as list[int].

Your Environment

• Mypy version used: 0.812
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.7.8
• Operating system and version: macOS 11.2.3