} else if lang_items.unsize_trait() == Some(def_id) {
self.assemble_candidates_for_unsizing(obligation, &mut candidates);
} else if lang_items.drop_trait() == Some(def_id)
- && obligation.predicate.skip_binder().constness == ty::BoundConstness::ConstIfConst
+ && obligation.predicate.is_const_if_const()
{
self.assemble_const_drop_candidates(obligation, &mut candidates);
} else {