Negative type narrowing fails for protocols with overloaded methods

[BvB93]

Bug Report

Since the merging of #9904 it is now possible to use runtime-checkable protocols with overloaded methods. While type narrowing now happens successfully with isinstance/issubclass checks in the positive case, the same does not hold for the negative case, be it either via not isinstance/not issubclass or a an else statement.

To Reproduce

from typing import overload, Protocol, runtime_checkable
from collections.abc import Sequence

class Foo:
    def func(self, a: int) -> float: ...

class FooOverload:
    @overload
    def func(self, a: int) -> float: ...
    @overload
    def func(self, a: str) -> Sequence[float]: ...

@runtime_checkable
class SupportsFunc(Protocol):
    @overload
    def func(self, a: int) -> float: ...
    @overload
    def func(self, a: str) -> Sequence[float]: ...

foo_union: FooOverload | Foo

Expected Behavior

if isinstance(foo_union, SupportsFunc):
    reveal_type(foo_union)  # N: Revealed type is '__main__.FooOverload'
else:
    reveal_type(foo_union)  # N: Revealed type is '__main__.Foo'

Observed Behavior

# NOTE: a `not isinstance` check also reveals a `Union`
if isinstance(foo_union, SupportsFunc):
    reveal_type(foo_union)  # N: Revealed type is '__main__.FooOverload'
else:
    reveal_type(foo_union)  # N: Revealed type is 'Union[__main__.FooOverload, __main__.Foo]'

Your Environment

• Mypy version used: master branch (post-b22c4e4)
• Mypy command-line flags: n.a.
• Mypy configuration options from mypy.ini (and other config files): n.a.
• Python version used: 3.10.2
• Operating system and version: Windows 10

[erictraut]

This bug was apparently fixed in mypy 0.981. Since then, it produces results consistent with the "expected behavior".

[hauntsaninja]

I think fixed by #13303