Support for ReifiedGenerics

[KotlinIsland]

Reified Generics in basedtyping need special casing in basedmypy.

isinstance and issubclass:

class Foo(ReifiedGeneric[T]): ...

isinstance(Foo[int](), Foo[int])

Ban TypeVars:

def foo(t: T):
    a: ReifiedList[T]  # should be an error

[DetachHead]

mypy doesnt need to be changed to accommodate for the ReifiedGenerics i'm adding to basedtyping

[DetachHead]

actually it does, since isinstance and issubclass have hardcoded functionality in mypy so we need to add logic to not show this error if it's a ReifiedGeneric

isinstance(Reified[int, str](), Reified[int, str])  # Parameterized generics cannot be used with class or instance checks  [misc]

[DetachHead]

i was originally going to makeour own is_instance function using a TypeGuard

_T_type = TypeVar("_T_type", bound=type)


@overload
def is_instance(__obj: object, __class_or_tuple: _T_type) -> TypeGuard[_T_type]:
    ...


@overload
def is_instance(
    __obj: object,
    __class_or_tuple: UnionType | tuple[type | UnionType | tuple[object, ...], ...],
) -> bool:
    ...


def is_instance(
    __obj: object,
    __class_or_tuple: type
    | UnionType
    | tuple[type | UnionType | tuple[object, ...], ...],
) -> bool:
    return isinstance(__obj, __class_or_tuple)

but that didn't work due to python#11428

[KotlinIsland]

I think modifying mypy checks are much better idea than making a typeguard

[DetachHead]

perhaps, but i prefer using existing functionality instead of intrinsic hidden behavior where possible. the fact that isinstance and issubclass don't even use TypeGuards seems very sus to me

[KotlinIsland]

imo TypeGuards are really broken atm and the intrinsic behavior is much better, so until typeguards are fixed I wouldn't bother.