The mrustc page says: > This project is a "simple" rust compiler written in C++ that is able to bootstrap a "recent" rustc, but may eventually become a full se

The mrustc page says: > This project is a "simple" rust compiler written in C++ that is able to bootstrap a "recent" rustc, but may eventually become a full separate re-implementation. So it's a compatible statement to say that it's currently a bootstrap compiler.