Auto and alias traits

1 files changed, 5 insertions, 0 deletions

diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index e68f27cc0fd..db7dd2e5e75 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -2382,6 +2382,11 @@ impl<'tcx> TyCtxt<'tcx> {
         self.trait_def(trait_def_id).has_auto_impl
     }
 
+    /// Returns `true` if this is a trait alias.
+    pub fn trait_is_alias(self, trait_def_id: DefId) -> bool {
+        self.def_kind(trait_def_id) == DefKind::TraitAlias
+    }
+
     pub fn trait_is_coinductive(self, trait_def_id: DefId) -> bool {
         self.trait_is_auto(trait_def_id) || self.lang_items().sized_trait() == Some(trait_def_id)
     }