Strictly speaking rustc has a dependency on LLVM, which is in C++, but you could use the rustc_codegen_cranelift backend [1] and get pretty much everything to be pure Rust. Unless you count the libc dependency, in which case, um, I guess you could use relibc [2]? And if you think relying on OS syscalls implemented in not-Rust is cheating, then you could just use Redox directly ;)
> And if you think relying on OS syscalls implemented in not-Rust is cheating, then you could just use Redox directly ;)
There's a problem though, the hard-drive firmware isn't written in rust, which is definitely cheating :P
I mean someone even managed to run linux on the harddrive, it's practically a whole extra computer we are using to build rust and it is undoubtedly programmed in C.