[Python-Dev] Re: PEP 647 (type guards) -- final call for comments

Current PEP 647 draft says:

"Some built-in type guards provide narrowing for both positive and negative tests (in both the if and else clauses)"

Should there be a separate (sub-?) type for those TypeGuards that *do* allow narrowing even on a False? Leaving it as an implementation detail available only to (some) built-in types seems to confuse the issue in both directions.

-jJ