error[E0308]: mismatched types
  --> $DIR/opaque-in-impl-is-opaque.rs:16:19
   |
LL |     fn bar(&self) -> impl Display {
   |                      ------------ the found opaque type
...
LL |     let x: &str = ().bar();
   |            ----   ^^^^^^^^ expected `&str`, found opaque type
   |            |
   |            expected due to this
   |
   = note: expected reference `&str`
            found opaque type `impl std::fmt::Display`

error: aborting due to previous error

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