So for the last couple of months or so, I’ve been hacking in my spare time on this library named salsa, along with a number of awesome other folks. Salsa basically extracts the incremental recompilation techniques that we built for rustc into a general-purpose framework that can be used by other programs. Salsa is developing quickly: with the publishing of v0.10.0, we saw a big step up in the overall ergonomics, and I think the current interface is starting to feel very nice.