@hongminhee I haven't compared all pairs but they catch slightly different typing errors, disagree with each other on what is an error and for the longest time, mypy found the most things that I agreed was an error. I imaging pyright has features optimized for syntax checking in an IDE, and pyrefly is optimized for slowly moving a large monorepo at facebook to being typed.

I'm betting ty is going to be a faster mypy, but I don't know. Just being a faster thing is astrals thing, tho.

@hongminhee Mypy can check types in Python metaprogramming patterns that other type checkers don't even try to handle. Typechecking Django models is one example.

@hongminhee MyPy is the reference implementation. You nailed it. And as others have mentioned, it does cover some tricky things that other checkers do not (precisely because they are tricky/hard to implement/slow)