12 Feb 2021 12 Feb '21
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.