from typing import Any, Self, overload, reveal_type

class Descriptor:
    @overload
    def __get__(self, instance: None, owner: type, /) -> Self: ...
    @overload
    def __get__[T](self, instance: T, owner: type | None = None, /) -> T: ...
    def __get__(self, instance: object, owner: type | None = None, /) -> Any: ...

class A:
    desc = Descriptor()

class Mixin:
    pass

def g(x: A) -> None:
    if isinstance(x, Mixin):
        reveal_type(x)  # Revealed type: `A & Mixin`
        reveal_type(x.desc)  # Revealed type: `A`
        reveal_type(A.desc.__get__(x))  # Revealed type: `A & Mixin`