If I change this line

to be

    try:
        _overload_registry[f.__module__][f.__qualname__][f.__code__.co_firstlineno] = func
    except AttributeError:
        # Not a normal function; ignore.
        raise # pass

test_typing continues to pass as expected. I think it is dangerous, because we can accidentally break something and not notice.

I will send a simple test case to catch this: we should not fail.