improving effectiveness of static typing

[0xalpharush]

As we increase type coverage it would be great to add something like the following to functions that should handle all types, effectively using mypy to alert when pattern matching isn't exhaustive. This will help catch issues earlier on when large changes are made e.g. to support a new solidity feature.

from typing import NoReturn

def assert_never(x: NoReturn) -> NoReturn:
    assert False, "Unhandled type: {}".format(type(x).__name__)

IntOrStr = int | str

def handle(x: IntOrStr) -> None:
    if isinstance(x, str):
        print(f"Handled {x}")
    else:
        assert_never(x)  # Error: "int" is incompatible with "NoReturn"

microsoft/pyright#2569