While I think rust has some serious issues with syntax (and I love rust), the things you've pointed out here are not rustisms, but programming language theory-i

While I think rust has some serious issues with syntax (and I love rust), the things you've pointed out here are not rustisms, but programming language theory-isms. x:Type has been used in MLs (SML, Ocaml) and recently TS. Haskells uses x::Type. This usage dates back to at least the simply typed lambda calculus in the 1930s. fn and fun are used in SML and probably elsewhere. fun is used in OCaml, as well.