borrow.rs

struct A<'a> {
    s: &'a String
}

struct B<'a> {
    a: A<'a>,
    s: String
}

impl<'a> B<'a> {
    fn new() -> B<'a> {
        let new_s = String::from("some string");
        let new_a = A {s: &new_s};
        return B {a: new_a, s: new_s};
    }

}

Error I'm getting (ignore the line numbers!)

error: `new_s` does not live long enough
  --> main.rs:18:28
   |
18 |         let new_a = A {s: &new_s};
   |                            ^^^^^ does not live long enough
19 |         return B {a: new_a, s: new_s};
20 |     }
   |     - borrowed value only lives until here
   |
note: borrowed value must be valid for the lifetime 'a as defined on the block at 16:22...
  --> main.rs:16:23
   |
16 |     fn new() -> B<'a> {
   |                       ^