Type parameters
Within the body of an item that has type parameter declarations, the names of its type parameters are types:
#![allow(unused)] fn main() { fn to_vec<A: Clone>(xs: &[A]) -> Vec<A> { if xs.is_empty() { return vec![]; } let first: A = xs[0].clone(); let mut rest: Vec<A> = to_vec(&xs[1..]); rest.insert(0, first); rest } }
Here, first has type A, referring to to_vec's A type parameter; and
rest has type Vec<A>, a vector with element type A.