Consider the following code (playground):

#[derive(Debug)]
struct Struct;

fn main() {
  let s = Struct;
  let mut v = Vec::new();
  v.push(&s);
  drop(s); // Error: cannot move out of `s` while `s` is borrowed
  println!("{:?}", v);
}

The compiler complains that drop(s) is illegal here because it attempts to move the value out of s while it is still borrowed. But how does the compiler know that the borrow of s lives a long as v and is therefore must still be valid when println!("{:?}", v); is called? What is it about the signature of Vec::push(&mut self, value: T) that tells the borrow checker that all pointees of reference-typed values must live at least as long as this Vec does?

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