error: unconstrained opaque type
  --> $DIR/issue-87258_b.rs:16:49
   |
LL | type Helper<'xenon, 'yttrium, KABOOM: Trait2> = impl Trait1;
   |                                                 ^^^^^^^^^^^
   |
   = note: `Helper` must be used in combination with a concrete type within the same module

error: aborting due to previous error