Add a helper function for checking whether a default function in a trait can be treated as `const`

1 files changed, 4 insertions, 2 deletions

diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
index b52ee817509..a18ddd42183 100644
--- a/compiler/rustc_ty_utils/src/ty.rs
+++ b/compiler/rustc_ty_utils/src/ty.rs
@@ -5,7 +5,7 @@ use rustc_middle::ty::subst::Subst;
 use rustc_middle::ty::{
     self, Binder, EarlyBinder, Predicate, PredicateKind, ToPredicate, Ty, TyCtxt,
 };
-use rustc_span::{sym, Span};
+use rustc_span::Span;
 use rustc_trait_selection::traits;
 
 fn sized_constraint_for_ty<'tcx>(
@@ -152,7 +152,9 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
 
     let constness = match hir_id {
         Some(hir_id) => match tcx.hir().get(hir_id) {
-            hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. }) if matches!(tcx.trait_of_item(def_id), Some(trait_id) if tcx.has_attr(trait_id, sym::const_trait)) => {
+            hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(..), .. })
+                if tcx.is_const_default_method(def_id) =>
+            {
                 hir::Constness::Const
             }