error: lifetime may not live long enough
  --> $DIR/unique-borrows-are-invariant-2.rs:15:17
   |
LL | impl<'b> Spooky<'b> {
   |      -- lifetime `'b` defined here
LL |     fn create_self_reference<'a>(&'a mut self) {
   |                              -- lifetime `'a` defined here
...
LL |                 self.borrowed = borrow;
   |                 ^^^^^^^^^^^^^^^^^^^^^^ assignment requires that `'a` must outlive `'b`
   |
   = help: consider adding the following bound: `'a: 'b`

error: aborting due to 1 previous error