I've always thought this was fascinating, but the only incremental compilation I knew was obscure programming languages and Rust. Oh yeah, I guess Roslyn?
Yeah I remember being in sophomore year of college, watching Anders Hejlsberg's video on "the new way to build compilers" or something and having my mind blown. But I only ever looked at the source code for Rust when it came to something actually implementing this, so that came to mind first.
Roslyn also has an extra constraint of integrating with live editing on the fly; I think you can get simpler and/or have different constraints if your requirement is only incremental compilation.