revert closer to the original check

Author: josetorrs

compiler/rustc_passes/src/dead.rs

@@ -438,9 +438,10 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
     fn should_ignore_impl_item(&mut self, impl_item: &hir::ImplItem<'_>) -> bool {
         if let hir::ImplItemImplKind::Trait { .. } = impl_item.impl_kind
             && let impl_of = self.tcx.local_parent(impl_item.owner_id.def_id)
+            && let trait_ref =
+                self.tcx.impl_trait_ref(impl_of).instantiate_identity().skip_norm_wip()
             && find_attr!(self.tcx, impl_item.owner_id.def_id, RustcTrivialFieldReads)
         {
-            let trait_ref = self.tcx.impl_trait_ref(impl_of).instantiate_identity().skip_norm_wip();
             if let ty::Adt(adt_def, _) = trait_ref.self_ty().kind()
                 && let Some(adt_def_id) = adt_def.did().as_local()
             {