What language was used to write Rust compiler? [duplicate]

Question

94% of Rust compiler was written in Rust. So I can't understand how is it possible? Because for compiling rustc you already must have some rust compiler. Can someone explain how it works and how rust compiler was created?

Answer 1

Simply put, once you have a compiler that compiles code, you can use that to develop and compile a new compiler. That new compiler can "understand" whatever language it's designed to compile.

So, suppose there was some C++ based rust compiler, and rust code was developed that compiles to a rust compiler, once you build that you have a rust based rust compiler.