multiple input types ("either / or") for option in python click

Is it possible to specify two input types for a click.option, one of which the supplied value has to be in?

In a normal python function with typing, I'd declare it like so:

from typing import Union

def fun(x: Union[int, str]):
    if isinstance(x, str):
        x = int(x)
    return x**2

so x should be either an int or str.

In click I want to achieve the same thing, just with the addition that the script fails when the input type isn't in the defined ones.

I've tried

@click.option('-x', type=(click.INT, click.STRING))

but that seems to be only for occasions with multiple arguments.