TypeError: Parameter list cannot be empty for TypeVarTuple

There is a problem with typing_extensions that doesn't happen with typing. Running the program with python3.11 works, but with python3.10 with typing_extensions throws:

Traceback (most recent call last):
  File ".../main.py", line 48, in <module>
    main()
  File ".../main.py", line 40, in main
    signal: Signal[()] = Signal[()]()
  File "/usr/lib/python3.10/typing.py", line 312, in inner
    return func(*args, **kwds)
  File "/usr/lib/python3.10/typing.py", line 1328, in __class_getitem__
    raise TypeError(
TypeError: Parameter list to Signal[...] cannot be empty

from __future__ import annotations

from typing_extensions import Callable, TypeVarTuple, Generic, Unpack, List, TypeVar

VarArgs = TypeVarTuple('VarArgs')


class Signal(Generic[Unpack[VarArgs]]):

    def __init__(self):
        self.functions: List[Callable[..., None]] = []
        """
        Simple mechanism that allows abstracted invocation of callbacks. Multiple callbacks can be attached to a signal
        so that they are all called when the signal is emitted.
        """

    def connect(self, function: Callable[..., None]):
        """
        Add a callback to this Signal
        :param function: callback to call when emited
        """
        self.functions.append(function)

    def emit(self, *args: Unpack[VarArgs]):
        """
        Call all callbacks with the arguments passed
        :param args: arguments for the signal, must be the same type as type parameter
        """
        for function in self.functions:
            if args:
                function(*args)
            else:
                function()


def main():
    def signalEmptyCall():
        print("Hello!")

    signal: Signal[()] = Signal[()]()

    signal.connect(signalEmptyCall)

    signal.emit()


if __name__ == '__main__':
    main()

main.py の再現コードから始め、Python 3.10 で typing_extensions を使用した場合と Python 3.11 で typing を使用した場合の Signal[()] の動作を比較します。TypeVarTuple と空のパラメーターの処理を追跡し、その後、空のパラメーターリストが一貫して受け入れられることを示す回帰テストを追加または更新します。