Inheriting class with __slots__ defined

• Are you reporting a bug, or opening a feature request?

Feature request

• Please insert below the code you are checking with mypy.

class Base():
    __slots__: List[str] = ['foo', 'bar']
    if TYPE_CHECKING:
        foo: int
        bar: int

class Derived(Base):
    __slots__: List[str] = ['bar']

• What is the actual behavior/output?

Success: no issues found in 1 source file

• What is the behavior/output you expect?

I believe it would be nice if mypy generated an error on __slots__ declaration in Derived class because 'bar' slot was already declared in Base class.

• What are the versions of mypy and Python you are using?

Python 3.8.0, mypy 0.761

Comienza reproduciendo con mypy el ejemplo proporcionado de Base y Derived con slots. Sigue cómo maneja el comprobador de tipos slots entre clases heredadas y, después, verifica que un slot heredado duplicado produzca un diagnóstico, mientras que las declaraciones de slots válidas sigan siendo aceptadas.