I’m trying to create a Mixin that assumes the child class has a certain variable that is of a generic type.
I use a Protocol to define that constraint on the mixin but mypy doesn’t seem to be able to resolve it.
Here is the most minimal version of my could I could get that reproduces the issue:

from abc import ABC, ABCMeta
from typing import Generic, Protocol, TypeVar


class MyOne:
    def __init__(self) -> None:
        pass


MyOneT = TypeVar("MyOneT", bound=MyOne)


class Foo(Generic[MyOneT], metaclass=ABCMeta):
    def __init__(self, my_var: MyOneT) -> None:
        self.my_var: MyOneT = my_var


Bar = Foo[MyOne]


class ChildBar(Bar, ABC):
    pass


class HasMyVarProtocol(Protocol[MyOneT]):
    my_var: MyOneT


class MyMixin(HasMyVarProtocol[MyOne]):
    def __init__(self) -> None:
        pass


class MyMainClass(ChildBar, MyMixin):
    def __init__(self, my_var: MyOne) -> None:
        super().__init__(my_var)

This produces the following error:

error: Definition of "my_var" in base class "Foo" is incompatible with definition in base class "HasMyVarProtocol"  [misc]
    class MyMainClass(ChildBar, MyMixin):

It seems mypy isn’t able to resolve that my_var are of the same generic type.