A long, long time ago, mighty matklad used to write great posts about how Rust tooling works. Those were great times, but alas, the last rust-analyzer blog post dates 2023 I am no matklad, but I'm building Rust Glancer , an experimental Rust LSP, for quite a while now. It's probably the most interesting and ambitious project I've worked on, and I want to share some things I've learned while working on it. This will be a (hopefully coherent) story about how Rust LSPs work, from the perspective of both rust-analyzer and Rust Glancer: how things that seem easy turn out to be hard, things that seem hard turn out to be even harder, and things I didn't expect to exist at all somehow do. Obviously, a single blog post can't cover everything, this will be a very technical but still architectural overview rather than a deep dive into any particular topic brought up along the way. Those will come as separate posts, granted I won't be lazy.…