error[E0276]: impl has stricter requirements than trait
  --> $DIR/region-extra-2.rs:19:5
   |
LL |     fn renew<'b: 'a>(self) -> &'b mut [T];
   |     -------------------------------------- definition of `renew` from trait
...
LL |     fn renew<'b: 'a>(self) -> &'b mut [T] where 'a: 'b {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl has extra requirement `'a: 'b`

error: aborting due to previous error

If you want more information on this error, try using "rustc --explain E0276"