Inconsistent "Invalid Metaclass" error for classes defined within functions

Bug Report

When a class:

• is defined inside a function, and
• uses a metaclass

then it mypy will inconsistently give an Invalid metaclass error based on whether the metaclass is specified via an alias name, or the original name from when the class is defined. This behaviour occurs regardless of whether the metaclass is defined inside or outside of the function. I would have expected no error.

To Reproduce

See on mypy playground

class M(type):
    pass


def f() -> None:
    _M = M

    class C(metaclass=_M): # Error
        pass
    
    class D(metaclass=M): # OK
        pass

Actual Behavior

main.py:8: error: Invalid metaclass "_M"  [misc]
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 1.1.1
• Python version used: 3.11

Inizia con il playground mypy collegato e la riproduzione con la funzione annidata, confrontando la metaclasse alias _M con il nome originale M. Traccia il controllo della metaclasse non valida e conferma che gli alias equivalenti non producono più diagnostica incoerente, mentre l’esempio non segnala alcun errore.