If the compiler gives you an error with a suggestion "You probably need to add `extern crate foo;`" (and it already does in some cases), RLS (i.e., your editor

If the compiler gives you an error with a suggestion "You probably need to add `extern crate foo;`" (and it already does in some cases), RLS (i.e., your editor plugin) will be able to automatically add it for you (soon™).