Callable with variadic fixed arguments that doesn't mean *args

Suppose I have a type of function called CommandHandler, that is a function that receives a command as its first parameter but then could have other parameters.
Examples

class Command:
    pass

class RegisterUser(Command):
    pass

class DeleteUser(Command):
    pass

def register_user(command: RegisterUser, db : Db) -> None:
    ...

def delete_user(command: DeleteUser, dispatch: EventDispatcher, cache: Cache) -> None:
    ...

mappings : dict[Command, CommandHandler] = {
    RegisterUser: register_user,
    DeleteUser: delete_user
}

What would be the definition of CommandHandler?

Ideally it would be:

C= TypeVar("C", bound=Command)
CommandHandler = Callable[[C, ...], None] 

But this syntax is not possible.

I've found in the documentation that Concatenate could receive ... at the end,

Concatenate is currently only valid when used as the first argument to a Callable. The last parameter to Concatenate must be a ParamSpec or ellipsis (...).

so it could be:

C= TypeVar("C", bound=Command)
CommandHandler = Callable[Concatenate[C, ...], None] 

But this returns an error from Pylance:

One could say Callback Protocol could solve this like:

C= TypeVar("C", bound=Command)
class CommandHandler(Protocol):
    def __call__(self, __command: C, *__args: Any) -> None: ...

But it only receives functions that has an implicit variadic argument, it doesn't work with variadic forms of the function.

So far the only way I could solve this is through the Union of many Callables, but it doesn't look like the best solution.

At the end CommandHandler can only be defined as:

C= TypeVar("C", bound=Command)
CommandHandler = Union[
    Callable[[C, Any], None],
    Callable[[C, Any, Any], None],
    Callable[[C, Any, Any, Any], None],
    Callable[[C, Any, Any, Any, Any], None],
    Callable[[C, Any, Any, Any, Any, Any], None],
    Callable[[C, Any, Any, Any, Any, Any, Any], None],
    Callable[[C, Any, Any, Any, Any, Any, Any, Any], None],
    Callable[
        [C, Any, Any, Any, Any, Any, Any, Any, Any], None
    ],
]

Related:
https://github.com/python/cpython/issues/88954
https://stackoverflow.com/questions/57658879/python-type-hint-for-callable-with-variable-number-of-str-same-type-arguments

Commencez par la documentation de Callable et Concatenate décrite dans l’issue, puis examinez l’issue associée 88954 et la discussion Stack Overflow liée. Comparez les formes de CommandHandler demandées avec les règles actuelles de typing et déterminez si une conception prise en charge permet de les exprimer ; le résultat doit inclure une spécification approuvée ainsi qu’un plan correspondant de documentation ou d’implémentation.