We’re building a new static type checker for Python, from scratch, in Rust.

From a technical perspective, it’s probably our most ambitious project yet. We’re about 800 PRs deep!

Like Ruff and uv, there will be a significant focus on performance.

The entire system is designed to be highly incremental so that it can eventually power a language server (e.g., only re-analyze affected files on code change).

Performance is just one of many goals, though.

For example: we're investing heavily in strong theoretical foundations and a consistent model of Python's typing semantics.

(We're lucky to have @carljm and @AlexWaygood on the team for many reasons, this is one of them.)

Another goal: minimizing false positives, especially on untyped code, to make it easier for projects to adopt a type checker and expand coverage gradually over time, without being swamped in bogus type errors from the start.

We haven't publicized it to-date, but all of this work has been happening in the open, in the Ruff repository.

All driven by a uniquely great team: @carljm, @AlexWaygood, @sharkdp86, @MichaReiser, @DhruvManilawala, @ibraheemdev, @dcreager.

I'm learning so much from them.

Warning: this project is not ready for real-world user testing, and certainly not for production use (yet). The core architecture is there, but we're still lacking support for some critical features.

Right now, I'd only recommend trying it out if you're looking to contribute.

For now, we're working towards an initial alpha release. When it's ready, I'll make sure you know :)

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[–] [email protected] 5 points 13 hours ago

Astral is already a Rust shop; uv and ruff are written in Rust, and it makes sense for them to expand on what's already considered very successful.

Rust can enable a lot of speed and "fearless concurrency"; it also has a pretty good type system and a focus on correctness. They'd rather be correct than fast (C made the other choice, but is also from another age), but also show that that extra correctness comes with little runtime speed cost (compilation is another story).