pyre-check

Pyre, written in OCaml, is the closest thing that's stable. It has been discussed on HN a couple of times. Here is the 2021 discussion: https://news.ycombinator.com/item?id=27107647. Note that Pyre does not support Windows (https://github.com/facebook/pyre-check/issues/554) and only provides wheels for x86_64 Linux and macOS (https://pypi.org/project/pyre-check/0.9.18/#files). While I don't use Windows, it makes me reluctant to adopt it. First, I want Windows users to be able to contribute to my projects that work on Windows. Mypy and (predictably) Pyright won't create an obstacle for Windows users. Second, the limited number of platforms makes Pyre seem a little internal-toolish. It may still be worth it. As of today, actually, one of my projects has a Pyre branch. I want to see what it is like developing with it.

https://github.com/facebook/pyre-check https://github.com/facebook/flow https://github.com/facebook/infer https://github.com/facebook/hhvm/tree/master/hphp/hack

Pyright is pretty recent and started development years after mypy. But some of pyright's design goals (laziness for LSP) would have made it very difficult to do in mypy without a very large refactor/rewrite. Pyright is implemented in typescript for better LSP/vscode integration and performance. pytype (google's type checker) is only one I know that predates mypy for when it started development. Pyre's reason is interesting, https://github.com/facebook/pyre-check/issues/38. Pyre is based off of Hack, facebook's php compiler. Facebook made pyre to re-use tooling/techniques from Hack on python. Secondary reason is performance. Pyre is done in OCaml and having same performance in type checker implemented within python is hard.

I can vouch for use of Pyright as LSP for neovim and helix. Very useful, especially the strict mode. I usually pair it with pyre, another great tool https://github.com/facebook/pyre-check