Redox OS, a microkernel OS written in Rust, hast just released version 0.0.6, which includes bug fixes and and update to Rust.
From the project’s 2016 in review post:
Today, we have a pretty mature project. It contains many core, usable components. It is already usable, but it is still not mature yet to be used as a replacement for Linux (like BSD is), but weâ??re slowly getting there.
The kernel was rewritten, a memory allocator was added, rendering libc out of the dependency chain, several applications were added, a file system were added, a window manager and display server was implemented, and so on.