compiler internals, optimizations
Improving rustc compilation performance (build times).
Working with LLVM upstream to represent Rust in its development
How compiler team organizes itself
Write MIR optimizations and refactor the MIR to be more optimizable.
Implementing the new MIR-based borrow check and non-lexical lifetimes
Making parallel compilation the default for rustc
Implementing profile-guided optimization for rustc
Make a closure capture individual fields of the variable rather than the entire composite variable
Experimenting with a new compiler architecture tailored for IDEs
Improving the -Z self-profile feature