Structs
Annotation of lifetimes in structures are also similar to functions:
// A type `Borrowed` which houses a reference to an// `i32`. The reference to `i32` must outlive `Borrowed`.#[derive(Debug)]struct Borrowed<'a>(&'a i32);// Similarly, both references here must outlive this structure.#[derive(Debug)]struct NamedBorrowed<'a> {x: &'a i32,y: &'a i32,}// An enum which is either an `i32` or a reference to one.#[derive(Debug)]enum Either<'a> {Num(i32),Ref(&'a i32),}fn main() {let x = 18;let y = 15;let single = Borrowed(&x);let double = NamedBorrowed { x: &x, y: &y };let reference = Either::Ref(&x);let number = Either::Num(y);println!("x is borrowed in {:?}", single);println!("x and y are borrowed in {:?}", double);println!("x is borrowed in {:?}", reference);println!("y is *not* borrowed in {:?}", number);}