[alkonaut]

Any lang that easily calls C and can be called by C, or can be compiled to C should be fine to use today.

Re: kernel - it's a lot of pretty simple subsystems. Each system is usually simpler (easier to verify and polish) than a lot of common libs doing really complex things (ssl, video codecs, ttf, ...). Complexity + raw pointers quickly add up to guaranteed problems.

Rust uses llvm. Use it for new development on any platform that llvm supports. A few microcontrollers might be left out.