error: lifetime may not live long enough
  --> $DIR/ex3-both-anon-regions-2.rs:2:5
   |
LL | fn foo(&mut (ref mut v, w): &mut (&u8, &u8), x: &u8) {
   |                                   -             - let's call the lifetime of this reference `'1`
   |                                   |
   |                                   let's call the lifetime of this reference `'2`
LL |     *v = x;
   |     ^^^^^^ assignment requires that `'1` must outlive `'2`
   |
help: consider introducing a named lifetime parameter
   |
LL | fn foo<'a>(&mut (ref mut v, w): &mut (&'a u8, &u8), x: &'a u8) {
   |       ++++                             ++               ++

error: aborting due to 1 previous error