`ClassVar` cannot contain `Self` type in generic classes

This rule seems correct when Self appears in a covariant position, like

class MyGeneric[T]:
    # ill-defined, what's the type of MySequence.example?
    example: ClassVar[Self]  # error: ClassVar cannot contain Self type in generic classes

However, if Self appears in a contravariant position, I do not see why this should be an error.

class MyGeneric[T]:
    pre_method_hooks: ClassVar[list[ Callable[[Self], None] ]] = []

Full example: https://mypy-play.net/?mypy=master&python=3.12&gist=951d5b3a168378cd33d9fc4aebd4572e

from typing import Callable, ClassVar, Self, Any
from abc import abstractmethod

class Transform[X, Y]:
    pre_transform_hooks: ClassVar[list[Callable[[Self], None]]] = []  # ❌️

    def __init_subclass__(cls) -> None:
        super().__init_subclass__()
        original_transform = cls.transform

        def wrapped_transform(self: Self, x: X, /, *args: Any, **kwargs: Any) -> Y:
            for hook in cls.pre_transform_hooks:
                hook(self)
            return original_transform(self, x, *args, **kwargs)
        cls.transform = wrapped_transform  # type: ignore[method-assign]

    @abstractmethod
    def transform(self, x: X, /) -> Y: ...

class Demo(Transform[int, int]):
    def transform(self, x: int, /) -> int: return 0

    def hello_world(self) -> None:
        print(f"Hello, world! from {self}")

    pre_transform_hooks: ClassVar[list[Callable]] = [hello_world]

Demo().transform(0)  # prints "Hello, world! from <__main__.Demo object at ...>"

main.py:5: error: ClassVar cannot contain Self type in generic classes  [misc]
Found 1 error in 1 file (checked 1 source file)

Reproduce el diagnóstico usando el ejemplo de mypy-play enlazado o el fragmento mostrado de main.py; después, sigue la validación de ClassVar y Self que rechaza el miembro de clase genérico. Compara los casos covariante y contravariante y revisa las pruebas existentes para esta regla. Se considera terminado cuando el caso contravariante previsto se gestiona de forma coherente, mientras que el caso covariante no válido sigue generando un diagnóstico.