R = typing.TypeVar('R')
E = typing.TypeVar('E')

@sum_type
class Result(typing.Generic[R, E]):
    """Experimental generic ADT."""

    __slots__ = ()

    Ok: Ctor[R]
    Err: Ctor[E]

my_result: Result[int, str] = Result.Ok(10)

@sum_type
class ConcreteResult:

    __slots__ = ()

    Ok: Ctor[int]
    Err: Ctor[str]

my_concrete_result: ConcreteResult = ConcreteResult.Ok(10)