Pyrefly is awesome. Anyone using Pyright (the default Python support in Cursor) should switch today.

Today I spent 8 hours to change 2 lines of code (github.com/facebook/pyref…). That involved:

* 30,342,810 line example that caused a crash
* 97 compilations
* 1.3Gb of log files
* 6 historic diffs
* 3 computers
* 2 whiteboards of notes

It's like a day long logic puzzle :)

New-ish @galois blog: “What Works (and Doesn't) Selling Formal Methods”. The boring truth: engineers are rational and adoption is all about cost/benefit tradeoffs

We landed a Zed extension for `pyrefly`, @facebook's new Python language server written in Rust. "Type check over 1.85 million lines of code per second" and receive other goodies, like go-to-definition.

🚀New Project Alert🚀

We recently launched an open source project, Pyrefly. It's a new type checker and IDE experience for Python. Lightweight, accurate, and designed for scale, Pyrefly is an excellent fit for your Python workflow!

Learn more: engineering.fb.com/2025/05/15/dev…

Pyrefly (our Python type checker) got a blog post (engineering.fb.com/2025/05/15/dev…) and podcast (open.spotify.com/episode/4JhEid…) today. Available from pyrefly.org if you want to give it a try.

Heading off to PyCon to talk about Pyrefly, the Python type checker I've been working on for the past 9 months. us.pycon.org/2025/schedule/…

I'll be talking at this about Buck2

Rust 1.85.0 has been released! 🌈🦀✨

Not only does this release add async closures, it also includes a whole new Rust Edition, Rust 2024! 🎆🚀

Check out the blog post for an overview of all the changes and additions: blog.rust-lang.org/2025/02/20/Rus…

HLint (Haskell linter) v3.10 out, which now works with GHC 9.8-9.12. A few little hints here and there too. hackage.haskell.org/package/hlint

I don't recommend developing two build systems, and then switching from one to the other, but that's what we at Jane Street accidentally did. And what a journey it was!

In the end, we're finally using Dune to build all our 70M+ lines of OCaml & Python 🙌

blog.janestreet.com/how-we-acciden…

This Linux-kernel-RCU bug fought well: people.kernel.org/8q9a9dt4q3

Very cool talk on building D binaries with Buck2 - youtube.com/live/AzezZhvIy… by Max Haughton

I’ve done a lot of formal methods “technical sales” - trying to scope projects for Galois clients that solve their problem and fit into a budget. I gave a talk last week on some things that I learned along the way: mikedodds.github.io/files/talks/20…

Released the Haskell extra library 1.8, now with support for the upcoming GHC 9.12. Mostly a lot of handy list functions - hackage.haskell.org/package/extra/…

My Haskell Uniplate library got ported to Rust - crates.io/crates/uniplate. Allows doing traversals by type, eg making it easy to work with big syntax trees. I've been using these ideas in Rust a while (eg github.com/facebook/starl…) but happily someone made them a proper library!

I finally wrote down my thoughts on the design of the LSP, both good and bad: michaelpj.com/blog/2024/09/0…

Got starlark-rust working with WASM/JS, so you can now run Starlark (approximately simplified Python) in your browser. Based on code from april.dev. PR at github.com/facebook/starl….

Haskell XML parsing library `hexml` (github.com/ndmitchell/hex…) gets an update after 6 years! Now supports <![CDATA[ ]]>, thanks to a contribution from mniip.com. Hexml is a very fast XML parser written in C, designed for easy wrapping as a fast Haskell XML library.

My 11yo made a platformer scratch game - scratch.mit.edu/projects/10098… - requires keyboard control. Finally a scratch game from him with a reasonable difficulty curve!