Incorrect type inferred for @property decorated functions

[mthuurne]

When mypy 0.740 is run on the following code:

class C:
    @property
    def prop(self) -> int:
        return 123

c = C()
print(c.prop)
getter = C.prop.__get__
print(getter(c))

It reports:

8: error: "Callable[[C], int]" has no attribute "__get__"

I think the problem is that, in general, mypy assumes decorators don't change the signature of the decorated function. When I ask it to reveal the type of C.prop, it reports def (self: testcase.C) -> builtins.int, which is the signature of the undecorated function, not of the property.

Since the property decorator is a built-in, it would be useful to have dedicated support for it in mypy.

[JukkaL]

This is essentially a duplicate of #6185.