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 aliases

TypeAlias :
   type IDENTIFIER Generics? WhereClause? = Type ;

A type alias defines a new name for an existing type. Type aliases are declared with the keyword type. Every value has a single, specific type, but may implement several different traits, or be compatible with several different type constraints.

For example, the following defines the type Point as a synonym for the type (u8, u8), the type of pairs of unsigned 8 bit integers:

# #![allow(unused_variables)]
#fn main() {
type Point = (u8, u8);
let p: Point = (41, 68);

A type alias to an enum type cannot be used to qualify the constructors:

# #![allow(unused_variables)]
#fn main() {
enum E { A }
type F = E;
let _: F = E::A;  // OK
// let _: F = F::A;  // Doesn't work