@property returning descriptor instance triggers false positive

🐛 Bug Report

Accessing a field implementing the descriptor protocol via a property method causes MyPy to complain that there is no matching overload for __get__().

To Reproduce

Run MyPy with all default settings on the following code:

from typing import Optional
from typing import overload
from typing import Type

class A:
    pass

class Field:
    def __init__(self, attr: Optional["Field"] = None):
        self.attr = attr

    @property
    def crashing_property(self) -> Optional["Field"]:
        return self.attr

    @overload
    def __get__(self, instance: None, owner: Type["A"]) -> "Field":
        ...

    @overload
    def __get__(self, instance: "A", owner: Type["A"]) -> Optional["Field"]:
        ...

    def __get__(self, instance, owner):
        if not instance:
            return self
        return self.attr

f = Field()  # type: Field
f.attr  # Works fine
f.crashing_property  # Triggers "no overload variant"

n.b. adding __set__() makes no difference

Expected Behavior

Accessing crashing_property shouldn't cause an error.

Actual Behavior

The last line in the example throws the following error:

test.py:39: error: No overload variant of "__get__" of "Field" matches argument types "Field", "Type[Field]"
test.py:39: note: Possible overload variants:
test.py:39: note:     def __get__(self, instance: None, owner: Type[A]) -> Field
test.py:39: note:     def __get__(self, instance: A, owner: Type[A]) -> Optional[Field]

If you add this the code validates fine:

@overload
def __get__(self, instance: "Field", owner: Type["Field"]):
    ...

Your Environment

• Mypy version used: 0.782, 0.800, 0.812, 0.910
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): None, using all defaults
• Python version used: CPython 3.7.7, 3.8.6, 3.9.1
• Operating system and version: Ubuntu 20.04, MacOS 11.1 (Big Sur)

Start by running the provided Python reproducer with MyPy's default settings and confirm the false-positive overload error on the property access. The work is done when that access validates without requiring an extra get overload for Field instances, while the existing descriptor behavior remains valid.