PEP 724: Stricter Type Guards

[NeilGirdhar]

@sirosen

These situations are real already with multiple type checkers. I’ve had threads where I learn that I’m using mypy and a maintainer is using pyright, and we get different types.

This is a really good point. Your desire for conformance to a standard may be shared by many people in typing, but as Jelle points out, diverging behavior may take a while to be resolved.

@sirosen

Run through my example scenario again with the introduction of StrictTypeGuard. Note how pyright would release support for StrictTypeGuard ahead of mypy, but my my_guards library would remain “correct” at all times under both type checkers.

Yes, but in this case there are very few people using type guards in a non-strict way. Additionally, those people should probably not be using type guards in a non-strict way in the first place.