error: lifetime may not live long enough
  --> $DIR/implied-bounds-on-nested-references-plus-variance-unnormalized.rs:12:5
   |
LL | fn extend<'a, 'b>(x: &'a str) -> &'b str {
   |           --  -- lifetime `'b` defined here
   |           |
   |           lifetime `'a` defined here
LL |     (extend_inner as fn(_) -> _)(x)
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ function was supposed to return data with lifetime `'b` but it is returning data with lifetime `'a`
   |
   = help: consider adding the following bound: `'a: 'b`

error: aborting due to 1 previous error