However, there's also something mentioned in this announcement: cargo-check. In terms of the "I'm building a project and I don't want my builds to be slow," I think that cargo-check might even be more important. cargo-check relies on an important insight: many times, when you're compiling, you don't actually care about producing a binary, you care that your code passes typechecking and other passes. cargo-check basically runs those things, and doesn't produce the final binary. Makes sense?