For now, this reference is a best-effort document. We strive for validity and completeness, but are not yet there. In the future, the docs and lang teams will work together to figure out how best to do this. Until then, this is a best-effort attempt. If you find something wrong or missing, file an issue or send in a pull request.

Type parameters

Within the body of an item that has type parameter declarations, the names of its type parameters are types:

# #![allow(unused_variables)]
#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);

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.