self type on property creates a spurious error

[JelleZijlstra]

Running mypy master on this file:

from typing import TypeVar, List
_T = TypeVar('_T')

class X:
    @property
    def __members__(self: _T) -> List[_T]: ...

reveal_type(X().__members__)

gives

../bin/selftypeproperty.py:8: error: Revealed type is 'builtins.list[selftypeproperty.X*]'
../bin/selftypeproperty.py:8: error: Invalid method type

The revealed type is correct but the "Invalid method type" doesn't make sense.

[gvanrossum]

Is it the same if you rename __members__ to foo?

[JelleZijlstra]

Yes, doesn't make a difference.

[elazarg]

I should look into it.

Note that adding a bound, i.e. _T = TypeVar('_T', bound='X') seems to fix this.

[JelleZijlstra]

Thanks! FYI, the code where I found this had a Type over a bound typevar (python/typeshed#1195). It has _T = TypeVar('_T', bound=Enum) and the property is def __members__(self: Type[_T]) -> Mapping[str, _T]: ....