Re: You spend a lot of time talking about C++
The subset of Rust they're referring to is you can't use stdlib just like you can't use clib in C. I assume for kernel work they'll have a lib of some sort, just not stdlib.
As for performance, it shouldn't be any different to C. Most of Rust's checks are at compile time and compile to zero runtime overhead. Rust and Clang also share the same backend so it produces gcc compatible .o files that can be linked together.