Container Dispatch

why?

Because this code doesnt work natively:

@dispatch.register
def _(arg: list[int|str]):
    return "this is a list of ints and strings!"

the stdlib functools.singledispatch returns:

TypeError: Invalid annotation for 'arg'. list[int|str] is not a class.

This means we have to simplify the annotation at the expense of complicating the function, and less support for mypy:

@dispatch.register
def _(arg: list):
    # list[int|str]
    if all(isinstance(i, (int,str)) for i in arg):
        return "this is a list of ints and strings!"

    # elif <other types>:
        # other logic

    else:
        # list[any]

Personally I find this antitheitcal to singledispatch, which is supposed to solve this exact problem! The entire reason I reached for singledispatch was to replace these if-ridden router functions, and I refused to accept this.