error[E0276]: impl has stricter requirements than trait
  --> $DIR/region-extra-2.rs:19:5
   |
15 |       fn renew<'b: 'a>(self) -> &'b mut [T];
   |       -------------------------------------- definition of `renew` from trait
...
19 |       fn renew<'b: 'a>(self) -> &'b mut [T] where 'a: 'b {
   |  _____^ starting here...
20 | |         //~^ ERROR E0276
21 | |         &mut self[..]
22 | |     }
   | |_____^ ...ending here: impl has extra requirement `'a: 'b`

error: aborting due to previous error