error: item does not constrain `Existential::{opaque#0}`
  --> $DIR/type-alias-impl-trait-in-fn-body.rs:8:4
   |
LL | fn main() {
   |    ^^^^
   |
   = note: consider removing `#[define_opaque]` or adding an empty `#[define_opaque()]`
note: this opaque type is supposed to be constrained
  --> $DIR/type-alias-impl-trait-in-fn-body.rs:10:24
   |
LL |     type Existential = impl Debug;
   |                        ^^^^^^^^^^

error: aborting due to 1 previous error