7 files changed, 53 insertions, 63 deletions

diff --git a/crates/hir_ty/src/db.rs b/crates/hir_ty/src/db.rs
index c198f6903..8a3cc0283 100644
--- a/crates/hir_ty/src/db.rs
+++ b/crates/hir_ty/src/db.rs
@@ -12,7 +12,7 @@ use la_arena::ArenaMap;
 use crate::{
     method_resolution::{InherentImpls, TraitImpls},
     traits::chalk,
-    Binders, CallableDefId, FnDefId, GenericPredicate, InferenceResult, OpaqueTyId, PolyFnSig,
+    Binders, CallableDefId, FnDefId, GenericPredicate, ImplTraitId, InferenceResult, PolyFnSig,
     ReturnTypeImplTraits, TraitRef, Ty, TyDefId, ValueTyDefId,
 };
 use hir_expand::name::Name;
@@ -83,7 +83,7 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
     #[salsa::interned]
     fn intern_type_param_id(&self, param_id: TypeParamId) -> InternedTypeParamId;
     #[salsa::interned]
-    fn intern_impl_trait_id(&self, id: OpaqueTyId) -> InternedOpaqueTyId;
+    fn intern_impl_trait_id(&self, id: ImplTraitId) -> InternedOpaqueTyId;
     #[salsa::interned]
     fn intern_closure(&self, id: (DefWithBodyId, ExprId)) -> InternedClosureId;
 
diff --git a/crates/hir_ty/src/display.rs b/crates/hir_ty/src/display.rs
index 0a13c8636..e6473586b 100644
--- a/crates/hir_ty/src/display.rs
+++ b/crates/hir_ty/src/display.rs
@@ -13,7 +13,7 @@ use hir_expand::name::Name;
 use crate::{
     db::HirDatabase, from_assoc_type_id, from_foreign_def_id, from_placeholder_idx, primitive,
     to_assoc_type_id, traits::chalk::from_chalk, utils::generics, AdtId, AliasTy, CallableDefId,
-    CallableSig, GenericPredicate, Interner, Lifetime, Obligation, OpaqueTy, OpaqueTyId,
+    CallableSig, GenericPredicate, ImplTraitId, Interner, Lifetime, Obligation, OpaqueTy,
     ProjectionTy, Scalar, Substs, TraitRef, Ty, TyKind,
 };
 
@@ -313,22 +313,26 @@ impl HirDisplay for Ty {
                     )?;
                 }
 
+                // FIXME: all this just to decide whether to use parentheses...
                 let datas;
                 let predicates = match t.interned(&Interner) {
                     TyKind::Dyn(predicates) if predicates.len() > 1 => {
                         Cow::Borrowed(predicates.as_ref())
                     }
-                    &TyKind::Alias(AliasTy::Opaque(OpaqueTy {
-                        opaque_ty_id: OpaqueTyId::ReturnTypeImplTrait(func, idx),
-                        ref parameters,
-                    })) => {
-                        datas =
-                            f.db.return_type_impl_traits(func).expect("impl trait id without data");
-                        let data = (*datas)
-                            .as_ref()
-                            .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
-                        let bounds = data.subst(parameters);
-                        Cow::Owned(bounds.value)
+                    &TyKind::Alias(AliasTy::Opaque(OpaqueTy { opaque_ty_id, 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 =
+                                f.db.return_type_impl_traits(func)
+                                    .expect("impl trait id without data");
+                            let data = (*datas)
+                                .as_ref()
+                                .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
+                            let bounds = data.subst(parameters);
+                            Cow::Owned(bounds.value)
+                        } else {
+                            Cow::Borrowed(&[][..])
+                        }
                     }
                     _ => Cow::Borrowed(&[][..]),
                 };
@@ -499,8 +503,9 @@ impl HirDisplay for Ty {
                 write!(f, "{}", type_alias.name)?;
             }
             TyKind::OpaqueType(opaque_ty_id, parameters) => {
-                match opaque_ty_id {
-                    &OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
+                let impl_trait_id = f.db.lookup_intern_impl_trait_id((*opaque_ty_id).into());
+                match impl_trait_id {
+                    ImplTraitId::ReturnTypeImplTrait(func, idx) => {
                         let datas =
                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
                         let data = (*datas)
@@ -510,7 +515,7 @@ impl HirDisplay for Ty {
                         write_bounds_like_dyn_trait_with_prefix("impl", &bounds.value, f)?;
                         // FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
                     }
-                    OpaqueTyId::AsyncBlockTypeImplTrait(..) => {
+                    ImplTraitId::AsyncBlockTypeImplTrait(..) => {
                         write!(f, "impl Future<Output = ")?;
                         parameters[0].hir_fmt(f)?;
                         write!(f, ">")?;
@@ -566,8 +571,9 @@ impl HirDisplay for Ty {
             }
             TyKind::Alias(AliasTy::Projection(p_ty)) => p_ty.hir_fmt(f)?,
             TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
-                match opaque_ty.opaque_ty_id {
-                    OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
+                let impl_trait_id = f.db.lookup_intern_impl_trait_id(opaque_ty.opaque_ty_id.into());
+                match impl_trait_id {
+                    ImplTraitId::ReturnTypeImplTrait(func, idx) => {
                         let datas =
                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
                         let data = (*datas)
@@ -576,7 +582,7 @@ impl HirDisplay for Ty {
                         let bounds = data.subst(&opaque_ty.parameters);
                         write_bounds_like_dyn_trait_with_prefix("impl", &bounds.value, f)?;
                     }
-                    OpaqueTyId::AsyncBlockTypeImplTrait(..) => {
+                    ImplTraitId::AsyncBlockTypeImplTrait(..) => {
                         write!(f, "{{async block}}")?;
                     }
                 };
diff --git a/crates/hir_ty/src/infer/expr.rs b/crates/hir_ty/src/infer/expr.rs
index 2e21d796c..eee3e6ec5 100644
--- a/crates/hir_ty/src/infer/expr.rs
+++ b/crates/hir_ty/src/infer/expr.rs
@@ -21,8 +21,8 @@ use crate::{
     to_assoc_type_id,
     traits::{chalk::from_chalk, FnTrait, InEnvironment},
     utils::{generics, variant_data, Generics},
-    AdtId, Binders, CallableDefId, FnPointer, FnSig, Interner, Obligation, OpaqueTyId, Rawness,
-    Scalar, Substs, TraitRef, Ty, TyKind,
+    AdtId, Binders, CallableDefId, FnPointer, FnSig, Interner, Obligation, Rawness, Scalar, Substs,
+    TraitRef, Ty, TyKind,
 };
 
 use super::{
@@ -179,7 +179,8 @@ impl<'a> InferenceContext<'a> {
                 // Use the first type parameter as the output type of future.
                 // existenail type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
                 let inner_ty = self.infer_expr(*body, &Expectation::none());
-                let opaque_ty_id = OpaqueTyId::AsyncBlockTypeImplTrait(self.owner, *body);
+                let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
+                let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
                 TyKind::OpaqueType(opaque_ty_id, Substs::single(inner_ty)).intern(&Interner)
             }
             Expr::Loop { body, label } => {
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index d1c018283..d6ff968f0 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -54,6 +54,7 @@ pub type ForeignDefId = chalk_ir::ForeignDefId<Interner>;
 pub type AssocTypeId = chalk_ir::AssocTypeId<Interner>;
 pub type FnDefId = chalk_ir::FnDefId<Interner>;
 pub type ClosureId = chalk_ir::ClosureId<Interner>;
+pub type OpaqueTyId = chalk_ir::OpaqueTyId<Interner>;
 pub type PlaceholderIndex = chalk_ir::PlaceholderIndex;
 
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
@@ -875,8 +876,8 @@ impl Ty {
     pub fn impl_trait_bounds(&self, db: &dyn HirDatabase) -> Option<Vec<GenericPredicate>> {
         match self.interned(&Interner) {
             TyKind::OpaqueType(opaque_ty_id, ..) => {
-                match opaque_ty_id {
-                    OpaqueTyId::AsyncBlockTypeImplTrait(def, _expr) => {
+                match db.lookup_intern_impl_trait_id((*opaque_ty_id).into()) {
+                    ImplTraitId::AsyncBlockTypeImplTrait(def, _expr) => {
                         let krate = def.module(db.upcast()).krate();
                         if let Some(future_trait) = db
                             .lang_item(krate, "future_trait".into())
@@ -894,12 +895,13 @@ impl Ty {
                             None
                         }
                     }
-                    OpaqueTyId::ReturnTypeImplTrait(..) => None,
+                    ImplTraitId::ReturnTypeImplTrait(..) => None,
                 }
             }
             TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
-                let predicates = match opaque_ty.opaque_ty_id {
-                    OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
+                let predicates = match db.lookup_intern_impl_trait_id(opaque_ty.opaque_ty_id.into())
+                {
+                    ImplTraitId::ReturnTypeImplTrait(func, idx) => {
                         db.return_type_impl_traits(func).map(|it| {
                             let data = (*it)
                                 .as_ref()
@@ -908,7 +910,7 @@ impl Ty {
                         })
                     }
                     // It always has an parameter for Future::Output type.
-                    OpaqueTyId::AsyncBlockTypeImplTrait(..) => unreachable!(),
+                    ImplTraitId::AsyncBlockTypeImplTrait(..) => unreachable!(),
                 };
 
                 predicates.map(|it| it.value)
@@ -1123,7 +1125,7 @@ impl<T: TypeWalk> TypeWalk for Vec<T> {
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
-pub enum OpaqueTyId {
+pub enum ImplTraitId {
     ReturnTypeImplTrait(hir_def::FunctionId, u16),
     AsyncBlockTypeImplTrait(hir_def::DefWithBodyId, ExprId),
 }
diff --git a/crates/hir_ty/src/lower.rs b/crates/hir_ty/src/lower.rs
index 78a914cac..e57d5970f 100644
--- a/crates/hir_ty/src/lower.rs
+++ b/crates/hir_ty/src/lower.rs
@@ -34,7 +34,7 @@ use crate::{
         make_mut_slice, variant_data,
     },
     AliasTy, Binders, BoundVar, CallableSig, DebruijnIndex, FnPointer, FnSig, GenericPredicate,
-    OpaqueTy, OpaqueTyId, PolyFnSig, ProjectionPredicate, ProjectionTy, ReturnTypeImplTrait,
+    ImplTraitId, OpaqueTy, PolyFnSig, ProjectionPredicate, ProjectionTy, ReturnTypeImplTrait,
     ReturnTypeImplTraits, Substs, TraitEnvironment, TraitRef, Ty, TyKind, TypeWalk,
 };
 
@@ -228,14 +228,12 @@ impl Ty {
                             Some(GenericDefId::FunctionId(f)) => f,
                             _ => panic!("opaque impl trait lowering in non-function"),
                         };
-                        let impl_trait_id = OpaqueTyId::ReturnTypeImplTrait(func, idx);
+                        let impl_trait_id = ImplTraitId::ReturnTypeImplTrait(func, idx);
+                        let opaque_ty_id = ctx.db.intern_impl_trait_id(impl_trait_id).into();
                         let generics = generics(ctx.db.upcast(), func.into());
                         let parameters = Substs::bound_vars(&generics, ctx.in_binders);
-                        TyKind::Alias(AliasTy::Opaque(OpaqueTy {
-                            opaque_ty_id: impl_trait_id,
-                            parameters,
-                        }))
-                        .intern(&Interner)
+                        TyKind::Alias(AliasTy::Opaque(OpaqueTy { opaque_ty_id, parameters }))
+                            .intern(&Interner)
                     }
                     ImplTraitLoweringMode::Param => {
                         let idx = ctx.impl_trait_counter.get();
diff --git a/crates/hir_ty/src/traits/chalk.rs b/crates/hir_ty/src/traits/chalk.rs
index e7217bc11..1f3e1c07a 100644
--- a/crates/hir_ty/src/traits/chalk.rs
+++ b/crates/hir_ty/src/traits/chalk.rs
@@ -177,10 +177,9 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
     }
 
     fn opaque_ty_data(&self, id: chalk_ir::OpaqueTyId<Interner>) -> Arc<OpaqueTyDatum> {
-        let interned_id = crate::db::InternedOpaqueTyId::from(id);
-        let full_id = self.db.lookup_intern_impl_trait_id(interned_id);
+        let full_id = self.db.lookup_intern_impl_trait_id(id.into());
         let bound = match full_id {
-            crate::OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
+            crate::ImplTraitId::ReturnTypeImplTrait(func, idx) => {
                 let datas = self
                     .db
                     .return_type_impl_traits(func)
@@ -202,7 +201,7 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
                 let num_vars = datas.num_binders;
                 make_binders(bound, num_vars)
             }
-            crate::OpaqueTyId::AsyncBlockTypeImplTrait(..) => {
+            crate::ImplTraitId::AsyncBlockTypeImplTrait(..) => {
                 if let Some((future_trait, future_output)) = self
                     .db
                     .lang_item(self.krate, "future_trait".into())
diff --git a/crates/hir_ty/src/traits/chalk/mapping.rs b/crates/hir_ty/src/traits/chalk/mapping.rs
index 460955756..2a66a2310 100644
--- a/crates/hir_ty/src/traits/chalk/mapping.rs
+++ b/crates/hir_ty/src/traits/chalk/mapping.rs
@@ -15,7 +15,7 @@ use crate::{
     primitive::UintTy,
     traits::{Canonical, Obligation},
     AliasTy, CallableDefId, FnPointer, FnSig, GenericPredicate, InEnvironment, OpaqueTy,
-    OpaqueTyId, ProjectionPredicate, ProjectionTy, Scalar, Substs, TraitRef, Ty,
+    ProjectionPredicate, ProjectionTy, Scalar, Substs, TraitRef, Ty,
 };
 
 use super::interner::*;
@@ -41,8 +41,7 @@ impl ToChalk for Ty {
                 chalk_ir::TyKind::AssociatedType(assoc_type_id, substitution).intern(&Interner)
             }
 
-            TyKind::OpaqueType(impl_trait_id, substs) => {
-                let id = impl_trait_id.to_chalk(db);
+            TyKind::OpaqueType(id, substs) => {
                 let substitution = substs.to_chalk(db);
                 chalk_ir::TyKind::OpaqueType(id, substitution).intern(&Interner)
             }
@@ -103,7 +102,7 @@ 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.to_chalk(db);
+                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,
@@ -125,9 +124,9 @@ impl ToChalk for Ty {
                 TyKind::Alias(AliasTy::Projection(ProjectionTy { associated_ty, parameters }))
             }
             chalk_ir::TyKind::Alias(chalk_ir::AliasTy::Opaque(opaque_ty)) => {
-                let impl_trait_id = from_chalk(db, opaque_ty.opaque_ty_id);
+                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: impl_trait_id, parameters }))
+                TyKind::Alias(AliasTy::Opaque(OpaqueTy { opaque_ty_id, parameters }))
             }
             chalk_ir::TyKind::Function(chalk_ir::FnPointer {
                 num_binders,
@@ -165,7 +164,7 @@ impl ToChalk for Ty {
             }
 
             chalk_ir::TyKind::OpaqueType(opaque_type_id, subst) => {
-                TyKind::OpaqueType(from_chalk(db, opaque_type_id), from_chalk(db, subst))
+                TyKind::OpaqueType(opaque_type_id, from_chalk(db, subst))
             }
 
             chalk_ir::TyKind::Scalar(scalar) => TyKind::Scalar(scalar),
@@ -268,21 +267,6 @@ impl ToChalk for hir_def::TraitId {
     }
 }
 
-impl ToChalk for OpaqueTyId {
-    type Chalk = chalk_ir::OpaqueTyId<Interner>;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::OpaqueTyId<Interner> {
-        db.intern_impl_trait_id(self).into()
-    }
-
-    fn from_chalk(
-        db: &dyn HirDatabase,
-        opaque_ty_id: chalk_ir::OpaqueTyId<Interner>,
-    ) -> OpaqueTyId {
-        db.lookup_intern_impl_trait_id(opaque_ty_id.into())
-    }
-}
-
 impl ToChalk for hir_def::ImplId {
     type Chalk = ImplId;