Use TyCtxt::is_fn_trait is a couple more places

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs

@@ -399,10 +399,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
                 self_ty.highlight.maybe_highlighting_region(vid, actual_has_vid);
 
                 if self_ty.value.is_closure()
-                    && self
-                        .tcx()
-                        .fn_trait_kind_from_def_id(expected_trait_ref.value.def_id)
-                        .is_some()
+                    && self.tcx().is_fn_trait(expected_trait_ref.value.def_id)
                 {
                     let closure_sig = self_ty.map(|closure| {
                         if let ty::Closure(_, substs) = closure.kind() {

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -1769,8 +1769,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 .enumerate()
                 .find(|(other_idx, (pred, _))| match pred.kind().skip_binder() {
                     ty::PredicateKind::Trait(trait_pred)
-                        if self.tcx.fn_trait_kind_from_def_id(trait_pred.def_id())
-                            .is_some()
+                        if self.tcx.is_fn_trait(trait_pred.def_id())
                             && other_idx != idx
                             // Make sure that the self type matches
                             // (i.e. constraining this closure)