Instance variables typed as `Callable` on the class body don't get assignment warnings when missing in `__slots__`

Bug Report, To Reproduce, & Actual Behaviour

See mypy Playground:

from collections.abc import Callable

class A:
    __slots__ = ()
    a: int
    b: Callable[[int], str]
    
    def __init__(self, /) -> None:
        self.a = 1  # E: Trying to assign name "a" that is not in "__slots__" of type "__main__.A"  [misc]
        self.b = lambda _: str(_)  # No warning

Expected Behavior

from collections.abc import Callable

class A:
    __slots__ = ()
    a: int
    b: Callable[[int], str]
    
    def __init__(self, /) -> None:
        self.a = 1  # E: Trying to assign name "a" that is not in "__slots__" of type "__main__.A"  [misc]
        self.b = lambda _: str(_)  # E: Trying to assign name "b" that is not in "__slots__" of type "__main__.A"  [misc]

Your Environment

• Mypy version used: (Occurs as far back as 1.0.0)
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.9, 3.12

Reproduce the example in the linked mypy Playground and compare the existing diagnostic for self.a with the missing diagnostic for self.b. Trace the __slots__ assignment-checking entry point and add regression coverage so the Callable-typed assignment receives the expected [misc] warning.