if let Some(trait_of) = self.tcx.trait_id_of_impl(impl_of)
&& self.tcx.has_attr(trait_of, sym::rustc_trivial_field_reads)
{
- let trait_ref = self.tcx.impl_trait_ref(impl_of).unwrap();
+ let trait_ref = self.tcx.impl_trait_ref(impl_of).unwrap().subst_identity();
if let ty::Adt(adt_def, _) = trait_ref.self_ty().kind()
&& let Some(adt_def_id) = adt_def.did().as_local()
{