[jasinjames]

Compilers are a good one. I know Rust's original compiler (before being self hosted) was implemented in OCaml. Darklang's compiler was in OCaml as well.

[delta_p_delta_x]

rustc targets LLVM IR by default, and I daresay the bulk of the optimisation and assembly-lowering work is done in LLVM. Which is solidly C++.