It is currently unstable and incomplete, which means you can activate it by adding the macros #![feature(specialization)] and #![allow(incomplete_features)] at the beginning of the file. But you have no guarantee that it will work the same way on the next version of rust.
I'm sorry, no wonder you are lost, so it made no sense when you wrote this comment, lemmy deleted everything between the "less than" character and ">". I had to change them for "<" in order for them not to get deleted.