ty is too permissive when I've tried it. It got better with time, and is maybe even quite ok now, but still, the ideology seems to be to allow anything it doesn't quite understand. Which just doesn't align well with my idea of what a type checker is supposed to do. Pyrefly has much better checks IME (at least with strict mode). On top of that, they have specific support for things like Polars schema checking and array shape checks also (supposedly - haven't tried the latter). Which are just incredible niceties.