[Typing-sig] Re: PEP 647 (type guards) -- final call for comments

Nothing about it is specific to TypeGuard, except that if TypeGuard is "compatible with bool", then it overlaps, and we get this behavior. It means that we can't rewrite existing functions in terms of TypeGuard, because we can't tell when a TypeGuard has been assigned to a bool and then distinguish it later. We have this issue already thanks to int/float conversions. I agree that this is good to note in the PEP.