How to alias `Annotated` to a subscriptable type

Hi, I want to create a type alias that simply wraps a tuple into Annotated.

PEP 593

I want to be able to write

SpecialReturn[int, bool, str]

And get

Annotated[Tuple[int, bool, str], 'special return!']

Among other things, I've tried:

class SpecialReturn():
    def __class_getitem__(self, params: Tuple[Any, ...]) -> Tuple[Any, ...]:
        return typing.cast(
            Tuple[Any, ...],
            _typing.Annotated[
                typing.Tuple.__getitem__(params),
                'multiple_return',
            ]
        )

Which mypy is happy with the declaration, but not using it:

import typing

from typing import Annotated, Any, Tuple


class SpecialReturn():
    def __class_getitem__(self, params: Tuple[Any, ...]) -> Tuple[Any, ...]:
        return typing.cast(
            Tuple[Any, ...],
            Annotated[
                typing.Tuple.__getitem__(params),
                'multiple_return',
            ]
        )


def test() -> SpecialReturn[int, int]:
    return 1, 2

test8.py:17: error: "SpecialReturn" expects no type arguments, but 2 given
test8.py:18: error: Incompatible return value type (got "Tuple[int, int]", expected "SpecialReturn")

Which happens because I guess mypy does not evaluate the type annotation, it just treats SpecialReturn as a separate type. I am not sure what is the reasoning behind this, but I assume there it makes sense in some way(?).

So, is there any alternative? How do achieve this? I essentially want to alias Tuple and be able to find out at runtime if the type is a normal tuple or my special one.

My first jab at this, and what I think makes most sense to a Python developer is the following

from typing import Tuple


class SpecialReturn(Tuple):
    pass


def test() -> SpecialReturn[int, int]:
    return 1, 2

But mypy can't handle it either:

test.py:4: error: Missing type parameters for generic type "Tuple"
test.py:8: error: "SpecialReturn" expects no type arguments, but 2 given
test.py:9: error: Incompatible return value type (got "Tuple[int, int]", expected "SpecialReturn")

I was thinking maybe something like this was possible with Annotated, but it seems not.

Beginne mit dem Lesen von PEP 593 und den Beispielen in diesem Issue und überprüfe anschließend, wie das typing project Annotated, generische Aliase und class_getitem darstellt. Das Issue nennt keine Datei, keinen Test und keinen Implementierungseinstiegspunkt; für den Abschluss müsste geklärt werden, ob dieses Verhalten unterstützt werden sollte und wie es spezifiziert werden sollte.