Shared via mypy Playground

main.py

from typing import Protocol

class Descriptor:
    def __get__(self, instance, owner) -> int:
        return 42

class Foo(Protocol):
    x: Descriptor = Descriptor()

class Bar(Protocol):
    @property
    def x(self) -> int:
        return 42

class HasX:
    def __init__(self) -> None:
        self.x: int = 42

def f(obj: Foo): ...
def g(obj: Bar): ...

f(HasX())
g(HasX())