error: lifetime may not live long enough
  --> $DIR/ex3-both-anon-regions-using-impl-items.rs:6:9
   |
LL |     fn foo(x: &mut Vec<&u8>, y: &u8) {
   |                        -        - let's call the lifetime of this reference `'1`
   |                        |
   |                        let's call the lifetime of this reference `'2`
LL |         x.push(y);
   |         ^^^^^^^^^ argument requires that `'1` must outlive `'2`
   |
help: consider introducing a named lifetime parameter and update trait if needed
   |
LL |     fn foo<'a>(x: &mut Vec<&'a u8>, y: &'a u8) {
   |           ++++              ++          ++

error: aborting due to 1 previous error