Just an FYI, for people looking at the low pass rates for mypy and ty and concluding they must not be very useful. These test suites are checking many odd corners of the typing spec.

For "normal" Python code, I find mypy does pretty good. Certainly I find it helpful, especially on a large code base and when working with other developers of various experience levels.

The reason I prefer pyrefly over mypy is mostly because of speed. Better accuracy is nice but speed it the killer feature. Given the quality of uv and ruff and the experience of the team working on ty, I'm quite confident it's going to be great in that respect as well.