isinstance(x, x2.__class__) fails type check

Bug Report

Mypy shows problems with taking a __class__ attribute and using this in isinstance check.

To Reproduce
Run mypy on the code below:

import itertools


class _MISSING:
    """Placeholder for missing values."""

    pass


def foo(x, x2) -> None:
    for t, t2 in itertools.zip_longest(x, x2, fillvalue=_MISSING):
        reveal_type(t)
        reveal_type(t2)
        a = isinstance(t, t2.__class__)

Expected Behavior

Check should pass

Actual Behavior

$ mypy simple.py                                                                                 (rlcore2) 12:44:04
simple.py:12: note: Revealed type is "Union[Any, def () -> simple._MISSING]"
simple.py:13: note: Revealed type is "Union[Any, def () -> simple._MISSING]"
simple.py:14: error: Argument 2 to "isinstance" has incompatible type "Union[Any, overloaded function]"; expected "Union[type, Tuple[Union[type, Tuple[Any, ...]], ...]]"  [arg-type]
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 0.982
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files):

[tool.mypy]
warn_unused_configs = true
allow_redefinition = true
disallow_untyped_defs = false
show_error_codes = true

• Python version used: Python 3.8.5

Inizia salvando la riproduzione come simple.py ed eseguendo mypy con la configurazione e l’ambiente Python 3.8.5 indicati. Traccia il modo in cui il checker inferisce t2.class per la chiamata a isinstance, quindi aggiungi un test di regressione che mostri che questo controllo passa senza l’errore arg-type segnalato.