IIRC there are native rust bindings for syscalls. The syscalls themselves are implemented in C++. I have no idea about the user space, but my impression is that rust is a first level language for things like the ui.
EDIT: it looks like they have interface generators for their APIs, which includes rust support as a first class citizen.
EDIT: it looks like they have interface generators for their APIs, which includes rust support as a first class citizen.