Type narrowing ClassVar in subclass prohibits a grandchild to use base type

[thejcannon]

Bug Report

I think the reproduction code speaks for itself 😅

To Reproduce

Playground URL: https://mypy-play.net/?mypy=latest&python=3.11&gist=333f013c023a7d031cf8ecfb30143bc3
Code:

from __future__ import annotations
from typing import ClassVar

class Foo:
    x: ClassVar[int | str]

class Bar(Foo):
    x = "s"

class Baz(Bar):
    x = 0  # womp womp

reveal_type(Baz.x)

Expected Behavior

The type didn't get narrowed when inheriting from Bar such that I can still assign x to int.

Note pyright doesn't have this particular affliction.

Actual Behavior

# Incompatible types in assignment (expression has type "int", base class "Bar" defined the type as "str") [assignment]

Your Environment

(See playground link))

[hauntsaninja]

Note that pyright isn't narrowing types (since it infers int | str, not int), it's using the context of the parent type to determine the type in the Bar class. This is a missing feature from mypy, but I'd track this in e.g. #10375