@cjgillot has been working to improve the query system used internally in
rustc which powers incremental compilation.
Some of their improvements have been to reduce unnecessary work performed during incremental compilation, leading to faster builds.
Other improvements have made the query system leaner allowing
rustc to bootstrap faster.
@cjgillot has also made many tweaks and optimizations to the query system.
@Nadrieril has been working on the pattern matching system resulting in improvements to compilation performance, code readability and related diagnostics generated by rustc. They have also been working on implementing features related to pattern matching like or-patterns and slice-patterns and helping push those features closer to stabilization.