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

Start by saving the reproduction as simple.py and running mypy with the reported Python 3.8.5 setup and configuration. Trace how the checker infers t2.class for the isinstance call, then add a regression test showing that this check passes without the reported arg-type error.