Rust naming: shortened identifiers conventions

I came to Rust from Java where very long and verbose identifiers are the norm. In Rust everything is much more chill, but are there any convention about what good contractions are?

For example, I have seen Ty* instead of Type* in rustc, and Arc, Rc, and other names in the standard library. However, are there any official or semiofficial documents which describe this?

For example, is it ok to shorten Reference to Ref, Make to Mk, Target to Tgt, or Context to Ctx?