Incorrect type narrowing for select class hierarchies  #16379

from __future__ import annotations


class A:
    pass


class B(A):
    def get_x(self):
        pass


class C(A):
    def get_x(self):
        pass


class D(C):
    pass


class E(C):
    pass


class F(C):
    pass


def x(obj: A):
    value = ""
    if isinstance(obj, B):
        value = obj.__class__.__name__
    elif isinstance(obj, D):
        value = obj.__class__.__name__
    elif isinstance(obj, E):
        value = obj.__class__.__name__
    elif isinstance(obj, F):
        value = obj.__class__.__name__
    else:
        raise RuntimeError("unhandled type")

    reveal_type(obj)
    obj.get_x()