error: lifetime may not live long enough
  --> $DIR/ex3-both-anon-regions-latebound-regions.rs:2:5
   |
LL | fn foo<'a,'b>(x: &mut Vec<&'a u8>, y: &'b u8) {
   |        -- -- lifetime `'b` defined here
   |        |
   |        lifetime `'a` defined here
LL |     x.push(y);
   |     ^^^^^^^^^ argument requires that `'b` must outlive `'a`
   |
   = help: consider adding the following bound: `'b: 'a`
   = note: requirement occurs because of a mutable reference to `Vec<&u8>`
   = note: mutable references are invariant over their type parameter
   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance

error: aborting due to 1 previous error