Implementing async-await

Improving rustc compilation performance (build times).

Make the compiler easier to learn by ensuring that rustc-guide and api docs are 'complete'

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

Experimental work on a new borrow-checker implementation

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

Revamping the rustc trait implementation to follow the Chalk approach.