error[E0308]: mismatched types
  --> $DIR/issue-88360.rs:15:9
   |
LL | trait SuperTrait<T>
   |                  - this type parameter
...
LL |     fn copy(&self) -> Self::Gat<'_> where T: Copy {
   |                       ------------- expected `&T` because of return type
LL |         *self.test()
   |         ^^^^^^^^^^^^ expected `&T`, found type parameter `T`
   |
   = note:   expected reference `&T`
           found type parameter `T`
help: consider removing deref here
   |
LL -         *self.test()
LL +         self.test()
   |

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.