One of the rust-analyzer co-maintainers (Chayim Friedman) already rewrote it, but we can’t integrate it yet, as about 40 assists (the little lightbulbs?) still rely on mutation. If you want something Rowan-like, I think syntree and Biome’s rowan fork are good options to look into.

How about cstree? https://crates.io/crates/cstree Recently I found that traversal in rowan tree can cost much time. No sure if there's a cheaper way to achieve that. Or, integrate rowan with bump allocator (bumpalo or oxc_allocator)?