1 files changed, 27 insertions, 1 deletions

diff --git a/crates/hir_ty/src/chalk_ext.rs b/crates/hir_ty/src/chalk_ext.rs
index b7463366b..0f4cb43e9 100644
--- a/crates/hir_ty/src/chalk_ext.rs
+++ b/crates/hir_ty/src/chalk_ext.rs
@@ -1,6 +1,11 @@
 //! Various extensions traits for Chalk types.
 
-use crate::{Interner, Ty, TyKind};
+use hir_def::{AssocContainerId, Lookup, TraitId};
+
+use crate::{
+    db::HirDatabase, from_assoc_type_id, to_chalk_trait_id, Interner, ProjectionTy, TraitRef, Ty,
+    TyKind,
+};
 
 pub trait TyExt {
     fn is_unit(&self) -> bool;
@@ -11,3 +16,24 @@ impl TyExt for Ty {
         matches!(self.kind(&Interner), TyKind::Tuple(0, _))
     }
 }
+
+pub trait ProjectionTyExt {
+    fn trait_ref(&self, db: &dyn HirDatabase) -> TraitRef;
+    fn trait_(&self, db: &dyn HirDatabase) -> TraitId;
+}
+
+impl ProjectionTyExt for ProjectionTy {
+    fn trait_ref(&self, db: &dyn HirDatabase) -> TraitRef {
+        TraitRef {
+            trait_id: to_chalk_trait_id(self.trait_(db)),
+            substitution: self.substitution.clone(),
+        }
+    }
+
+    fn trait_(&self, db: &dyn HirDatabase) -> TraitId {
+        match from_assoc_type_id(self.associated_ty_id).lookup(db.upcast()).container {
+            AssocContainerId::TraitId(it) => it,
+            _ => panic!("projection ty without parent trait"),
+        }
+    }
+}