4 files changed, 22 insertions, 18 deletions

diff --git a/crates/hir_ty/src/display.rs b/crates/hir_ty/src/display.rs
index 21291ddda..378c951c5 100644
--- a/crates/hir_ty/src/display.rs
+++ b/crates/hir_ty/src/display.rs
@@ -319,7 +319,10 @@ impl HirDisplay for Ty {
                     TyKind::Dyn(predicates) if predicates.len() > 1 => {
                         Cow::Borrowed(predicates.as_ref())
                     }
-                    &TyKind::Alias(AliasTy::Opaque(OpaqueTy { opaque_ty_id, ref parameters })) => {
+                    &TyKind::Alias(AliasTy::Opaque(OpaqueTy {
+                        opaque_ty_id,
+                        substitution: ref parameters,
+                    })) => {
                         let impl_trait_id = f.db.lookup_intern_impl_trait_id(opaque_ty_id.into());
                         if let ImplTraitId::ReturnTypeImplTrait(func, idx) = impl_trait_id {
                             datas =
@@ -579,7 +582,7 @@ impl HirDisplay for Ty {
                         let data = (*datas)
                             .as_ref()
                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
-                        let bounds = data.subst(&opaque_ty.parameters);
+                        let bounds = data.subst(&opaque_ty.substitution);
                         write_bounds_like_dyn_trait_with_prefix("impl", &bounds.value, f)?;
                     }
                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index bc7a7369a..484652073 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -66,7 +66,7 @@ pub enum Lifetime {
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub struct OpaqueTy {
     pub opaque_ty_id: OpaqueTyId,
-    pub parameters: Substs,
+    pub substitution: Substs,
 }
 
 /// A "projection" type corresponds to an (unnormalized)
@@ -903,7 +903,7 @@ impl Ty {
                             let data = (*it)
                                 .as_ref()
                                 .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
-                            data.subst(&opaque_ty.parameters)
+                            data.subst(&opaque_ty.substitution)
                         })
                     }
                     // It always has an parameter for Future::Output type.
@@ -1059,7 +1059,7 @@ impl TypeWalk for Ty {
                 }
             }
             TyKind::Alias(AliasTy::Opaque(o_ty)) => {
-                for t in o_ty.parameters.iter() {
+                for t in o_ty.substitution.iter() {
                     t.walk(f);
                 }
             }
@@ -1094,7 +1094,7 @@ impl TypeWalk for Ty {
                 }
             }
             TyKind::Alias(AliasTy::Opaque(o_ty)) => {
-                o_ty.parameters.walk_mut_binders(f, binders);
+                o_ty.substitution.walk_mut_binders(f, binders);
             }
             _ => {
                 if let Some(substs) = self.substs_mut() {
diff --git a/crates/hir_ty/src/lower.rs b/crates/hir_ty/src/lower.rs
index 76b2124af..d026310f4 100644
--- a/crates/hir_ty/src/lower.rs
+++ b/crates/hir_ty/src/lower.rs
@@ -230,8 +230,11 @@ impl<'a> TyLoweringContext<'a> {
                         let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
                         let generics = generics(self.db.upcast(), func.into());
                         let parameters = Substs::bound_vars(&generics, self.in_binders);
-                        TyKind::Alias(AliasTy::Opaque(OpaqueTy { opaque_ty_id, parameters }))
-                            .intern(&Interner)
+                        TyKind::Alias(AliasTy::Opaque(OpaqueTy {
+                            opaque_ty_id,
+                            substitution: parameters,
+                        }))
+                        .intern(&Interner)
                     }
                     ImplTraitLoweringMode::Param => {
                         let idx = self.impl_trait_counter.get();
diff --git a/crates/hir_ty/src/traits/chalk/mapping.rs b/crates/hir_ty/src/traits/chalk/mapping.rs
index 1a6fca611..05a4bf0df 100644
--- a/crates/hir_ty/src/traits/chalk/mapping.rs
+++ b/crates/hir_ty/src/traits/chalk/mapping.rs
@@ -87,6 +87,13 @@ impl ToChalk for Ty {
                 .cast(&Interner)
                 .intern(&Interner)
             }
+            TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
+                let opaque_ty_id = opaque_ty.opaque_ty_id;
+                let substitution = opaque_ty.substitution.to_chalk(db);
+                chalk_ir::AliasTy::Opaque(chalk_ir::OpaqueTy { opaque_ty_id, substitution })
+                    .cast(&Interner)
+                    .intern(&Interner)
+            }
             TyKind::Placeholder(idx) => idx.to_ty::<Interner>(&Interner),
             TyKind::BoundVar(idx) => chalk_ir::TyKind::BoundVar(idx).intern(&Interner),
             TyKind::InferenceVar(..) => panic!("uncanonicalized infer ty"),
@@ -101,15 +108,6 @@ impl ToChalk for Ty {
                 };
                 chalk_ir::TyKind::Dyn(bounded_ty).intern(&Interner)
             }
-            TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
-                let opaque_ty_id = opaque_ty.opaque_ty_id;
-                let substitution = opaque_ty.parameters.to_chalk(db);
-                chalk_ir::TyKind::Alias(chalk_ir::AliasTy::Opaque(chalk_ir::OpaqueTy {
-                    opaque_ty_id,
-                    substitution,
-                }))
-                .intern(&Interner)
-            }
             TyKind::Unknown => chalk_ir::TyKind::Error.intern(&Interner),
         }
     }
@@ -129,7 +127,7 @@ impl ToChalk for Ty {
             chalk_ir::TyKind::Alias(chalk_ir::AliasTy::Opaque(opaque_ty)) => {
                 let opaque_ty_id = opaque_ty.opaque_ty_id;
                 let parameters = from_chalk(db, opaque_ty.substitution);
-                TyKind::Alias(AliasTy::Opaque(OpaqueTy { opaque_ty_id, parameters }))
+                TyKind::Alias(AliasTy::Opaque(OpaqueTy { opaque_ty_id, substitution: parameters }))
             }
             chalk_ir::TyKind::Function(chalk_ir::FnPointer {
                 num_binders,