error[E0308]: mismatched types
  --> $DIR/issue-57673-ice-on-deref-of-boxed-trait.rs:5:5
   |
LL | fn ice(x: Box<dyn Iterator<Item=()>>) {
   |                                       - possibly return type missing here?
LL |     *x
   |     ^^ expected `()`, found trait `std::iter::Iterator`
   |
   = note: expected unit type `()`
           found trait object `(dyn std::iter::Iterator<Item = ()> + 'static)`

error: aborting due to previous error

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