Fix @classproperty decorator

[intgr]

Removed unnecessary Self hints on classproperty methods.

Related issues

The removal of self: Self fixes #1285. Regressed in #1253.

[sobolevn]

Now Self seems unbound. It can be Any

[intgr]

I don't actually understand how this mechanism works 😆 I just reverted the unwanted changes and verified via the test that it works.

If I add self: Self here, it no longer works.

[sobolevn]

mypy binds variables in two cases:

1. If they are in Generic[] definition, like we have here with _Get
2. If it is used more than once in a function: def some(a: A) -> A: return a

Here Self is unbound and should be changed to Any with a comment, I guess.

[djbrown]

maybe it could be done like in python/typeshed stdlib/builtins.pyi classmethod

_R_co = TypeVar("_R_co", covariant=True)
...
class classmethod(Generic[_R_co]):
    @property
    def __func__(self) -> Callable[..., _R_co]: ...
    @property
    def __isabstractmethod__(self) -> bool: ...
    def __init__(self: classmethod[_R_co], __f: Callable[..., _R_co]) -> None: ...
    def __get__(self, __obj: _T, __type: type[_T] | None = ...) -> Callable[..., _R_co]: ...
    if sys.version_info >= (3, 10):
        __name__: str
        __qualname__: str
        @property
        def __wrapped__(self) -> Callable[..., _R_co]: ...

PEP 673 - Self Type describes Self as shorthand for: TClassName = TypeVar("TClassName", bound="ClassName"). So maybe covariant TypeVar would be the fix here?
Also PEP 673 was only just introducted in python 3.11. Maybe that could be a problem too?

[djbrown]

But then again djangos classproperty is implemented a bit differently than CPythons classmethod

[djbrown]

I just saw that _Get already is the covariant TypeVar, so that should be fine.
Looking at the typehints for @property I think I now understand what @sobolevn means (simply replace the remaining Self with Any):

    fget: Callable[[Any], _Get] | None
    def __init__(self, method: Callable[[Any], _Get] | None = ...) -> None: ...
    def __get__(self, instance: Any | None, cls: type[Any] = ...) -> _Get: ...
    def getter(self, method: Callable[[Any], _Get]) -> classproperty[_Get]: ...

[intgr]

Indeed works just as well with Any. I've pushed this change.

[djbrown]

LGTM and the fix works locally for me :)