There’s a few hundred thousand lines of Rust in Fuchsia. (Garnet’s repo claims 12% Rust as of today.) They’ve been hiring Rust programmers aggressively to add more. They’ve been helping drive the design and implementation of async/await, since they’re big users. Rust is one of the four or five languages that they maintain a sort-of-libc for and use it as an example for writing applications for the OS. (It’s a microkernel, so it’s not really a libc so much as it is their IPC layer, which is how you make the equivalent of syscalls in other languages. “FIDL”)