Bug report

Bug description:

#103034 added some protections around isinstance checks of runtime_checkable Protocols using inspect.getattr_static. This uses inspect._check_instance which uses object.__getattribute__(obj, "__dict__"), which fails for bound instance methods (although obj.__dict__ does work), so they cannot fulfill runtime_checkable Protocols anymore.

from typing import Protocol, runtime_checkable


@runtime_checkable
class Labelled(Protocol):
    label: str


class A:
    def f(self):
        pass


A.f.label = "f"

a = A()
print(a.f.__dict__)  # {'label': 'f'}
print(object.__getattribute__(a.f, "__dict__"))  # AttributeError

assert isinstance(a.f, Labelled)  # AssertionError

Is this an intended/known change? Could it be noted in the changelog here as an example of case that will no longer work?

Created from #103034 (comment)
cc @AlexWaygood

CPython versions tested on:

3.12

Operating systems tested on:

Linux