1 files changed, 358 insertions, 347 deletions

diff --git a/crates/hir_ty/src/lower.rs b/crates/hir_ty/src/lower.rs
index 5fa83567b..c32dca9d7 100644
--- a/crates/hir_ty/src/lower.rs
+++ b/crates/hir_ty/src/lower.rs
@@ -8,7 +8,7 @@
 use std::{iter, sync::Arc};
 
 use base_db::CrateId;
-use chalk_ir::Mutability;
+use chalk_ir::{cast::Cast, Mutability};
 use hir_def::{
     adt::StructKind,
     builtin_type::BuiltinType,
@@ -27,13 +27,15 @@ use stdx::impl_from;
 
 use crate::{
     db::HirDatabase,
+    to_assoc_type_id, to_placeholder_idx,
+    traits::chalk::{Interner, ToChalk},
     utils::{
         all_super_trait_refs, associated_type_by_name_including_super_traits, generics,
         make_mut_slice, variant_data,
     },
     AliasTy, Binders, BoundVar, CallableSig, DebruijnIndex, FnPointer, FnSig, GenericPredicate,
-    OpaqueTy, OpaqueTyId, PolyFnSig, ProjectionPredicate, ProjectionTy, ReturnTypeImplTrait,
-    ReturnTypeImplTraits, Substs, TraitEnvironment, TraitRef, Ty, TypeWalk,
+    ImplTraitId, OpaqueTy, PolyFnSig, ProjectionPredicate, ProjectionTy, ReturnTypeImplTrait,
+    ReturnTypeImplTraits, Substs, TraitEnvironment, TraitRef, Ty, TyKind, TypeWalk,
 };
 
 #[derive(Debug)]
@@ -138,69 +140,71 @@ pub enum TypeParamLoweringMode {
     Variable,
 }
 
-impl Ty {
-    pub fn from_hir(ctx: &TyLoweringContext<'_>, type_ref: &TypeRef) -> Self {
-        Ty::from_hir_ext(ctx, type_ref).0
+impl<'a> TyLoweringContext<'a> {
+    pub fn lower_ty(&self, type_ref: &TypeRef) -> Ty {
+        self.lower_ty_ext(type_ref).0
     }
-    pub fn from_hir_ext(ctx: &TyLoweringContext<'_>, type_ref: &TypeRef) -> (Self, Option<TypeNs>) {
+
+    fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option<TypeNs>) {
         let mut res = None;
         let ty = match type_ref {
-            TypeRef::Never => Ty::Never,
+            TypeRef::Never => TyKind::Never.intern(&Interner),
             TypeRef::Tuple(inner) => {
-                let inner_tys: Arc<[Ty]> = inner.iter().map(|tr| Ty::from_hir(ctx, tr)).collect();
-                Ty::Tuple(inner_tys.len(), Substs(inner_tys))
+                let inner_tys: Arc<[Ty]> = inner.iter().map(|tr| self.lower_ty(tr)).collect();
+                TyKind::Tuple(inner_tys.len(), Substs(inner_tys)).intern(&Interner)
             }
             TypeRef::Path(path) => {
-                let (ty, res_) = Ty::from_hir_path(ctx, path);
+                let (ty, res_) = self.lower_path(path);
                 res = res_;
                 ty
             }
             TypeRef::RawPtr(inner, mutability) => {
-                let inner_ty = Ty::from_hir(ctx, inner);
-                Ty::Raw(lower_to_chalk_mutability(*mutability), Substs::single(inner_ty))
+                let inner_ty = self.lower_ty(inner);
+                TyKind::Raw(lower_to_chalk_mutability(*mutability), Substs::single(inner_ty))
+                    .intern(&Interner)
             }
             TypeRef::Array(inner) => {
-                let inner_ty = Ty::from_hir(ctx, inner);
-                Ty::Array(Substs::single(inner_ty))
+                let inner_ty = self.lower_ty(inner);
+                TyKind::Array(Substs::single(inner_ty)).intern(&Interner)
             }
             TypeRef::Slice(inner) => {
-                let inner_ty = Ty::from_hir(ctx, inner);
-                Ty::Slice(Substs::single(inner_ty))
+                let inner_ty = self.lower_ty(inner);
+                TyKind::Slice(Substs::single(inner_ty)).intern(&Interner)
             }
             TypeRef::Reference(inner, _, mutability) => {
-                let inner_ty = Ty::from_hir(ctx, inner);
-                Ty::Ref(lower_to_chalk_mutability(*mutability), Substs::single(inner_ty))
+                let inner_ty = self.lower_ty(inner);
+                TyKind::Ref(lower_to_chalk_mutability(*mutability), Substs::single(inner_ty))
+                    .intern(&Interner)
             }
-            TypeRef::Placeholder => Ty::Unknown,
+            TypeRef::Placeholder => TyKind::Unknown.intern(&Interner),
             TypeRef::Fn(params, is_varargs) => {
-                let substs = Substs(params.iter().map(|tr| Ty::from_hir(ctx, tr)).collect());
-                Ty::Function(FnPointer {
+                let substs = Substs(params.iter().map(|tr| self.lower_ty(tr)).collect());
+                TyKind::Function(FnPointer {
                     num_args: substs.len() - 1,
                     sig: FnSig { variadic: *is_varargs },
                     substs,
                 })
+                .intern(&Interner)
             }
             TypeRef::DynTrait(bounds) => {
-                let self_ty = Ty::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0));
-                let predicates = ctx.with_shifted_in(DebruijnIndex::ONE, |ctx| {
-                    bounds
-                        .iter()
-                        .flat_map(|b| GenericPredicate::from_type_bound(ctx, b, self_ty.clone()))
-                        .collect()
+                let self_ty =
+                    TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
+                let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
+                    bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone())).collect()
                 });
-                Ty::Dyn(predicates)
+                TyKind::Dyn(predicates).intern(&Interner)
             }
             TypeRef::ImplTrait(bounds) => {
-                match ctx.impl_trait_mode {
+                match self.impl_trait_mode {
                     ImplTraitLoweringMode::Opaque => {
-                        let idx = ctx.impl_trait_counter.get();
-                        ctx.impl_trait_counter.set(idx + 1);
+                        let idx = self.impl_trait_counter.get();
+                        self.impl_trait_counter.set(idx + 1);
 
-                        assert!(idx as usize == ctx.opaque_type_data.borrow().len());
+                        assert!(idx as usize == self.opaque_type_data.borrow().len());
                         // this dance is to make sure the data is in the right
                         // place even if we encounter more opaque types while
                         // lowering the bounds
-                        ctx.opaque_type_data
+                        self.opaque_type_data
                             .borrow_mut()
                             .push(ReturnTypeImplTrait { bounds: Binders::new(1, Vec::new()) });
                         // We don't want to lower the bounds inside the binders
@@ -212,65 +216,67 @@ impl Ty {
                         // other, but separately. So if the `T` refers to a type
                         // parameter of the outer function, it's just one binder
                         // away instead of two.
-                        let actual_opaque_type_data = ctx
+                        let actual_opaque_type_data = self
                             .with_debruijn(DebruijnIndex::INNERMOST, |ctx| {
-                                ReturnTypeImplTrait::from_hir(ctx, &bounds)
+                                ctx.lower_impl_trait(&bounds)
                             });
-                        ctx.opaque_type_data.borrow_mut()[idx as usize] = actual_opaque_type_data;
+                        self.opaque_type_data.borrow_mut()[idx as usize] = actual_opaque_type_data;
 
-                        let func = match ctx.resolver.generic_def() {
+                        let func = match self.resolver.generic_def() {
                             Some(GenericDefId::FunctionId(f)) => f,
                             _ => panic!("opaque impl trait lowering in non-function"),
                         };
-                        let impl_trait_id = OpaqueTyId::ReturnTypeImplTrait(func, idx);
-                        let generics = generics(ctx.db.upcast(), func.into());
-                        let parameters = Substs::bound_vars(&generics, ctx.in_binders);
-                        Ty::Alias(AliasTy::Opaque(OpaqueTy {
-                            opaque_ty_id: impl_trait_id,
-                            parameters,
-                        }))
+                        let impl_trait_id = ImplTraitId::ReturnTypeImplTrait(func, idx);
+                        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)
                     }
                     ImplTraitLoweringMode::Param => {
-                        let idx = ctx.impl_trait_counter.get();
+                        let idx = self.impl_trait_counter.get();
                         // FIXME we're probably doing something wrong here
-                        ctx.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
-                        if let Some(def) = ctx.resolver.generic_def() {
-                            let generics = generics(ctx.db.upcast(), def);
+                        self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
+                        if let Some(def) = self.resolver.generic_def() {
+                            let generics = generics(self.db.upcast(), def);
                             let param = generics
                                 .iter()
                                 .filter(|(_, data)| {
                                     data.provenance == TypeParamProvenance::ArgumentImplTrait
                                 })
                                 .nth(idx as usize)
-                                .map_or(Ty::Unknown, |(id, _)| Ty::Placeholder(id));
-                            param
+                                .map_or(TyKind::Unknown, |(id, _)| {
+                                    TyKind::Placeholder(to_placeholder_idx(self.db, id))
+                                });
+                            param.intern(&Interner)
                         } else {
-                            Ty::Unknown
+                            TyKind::Unknown.intern(&Interner)
                         }
                     }
                     ImplTraitLoweringMode::Variable => {
-                        let idx = ctx.impl_trait_counter.get();
+                        let idx = self.impl_trait_counter.get();
                         // FIXME we're probably doing something wrong here
-                        ctx.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
+                        self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
                         let (parent_params, self_params, list_params, _impl_trait_params) =
-                            if let Some(def) = ctx.resolver.generic_def() {
-                                let generics = generics(ctx.db.upcast(), def);
+                            if let Some(def) = self.resolver.generic_def() {
+                                let generics = generics(self.db.upcast(), def);
                                 generics.provenance_split()
                             } else {
                                 (0, 0, 0, 0)
                             };
-                        Ty::BoundVar(BoundVar::new(
-                            ctx.in_binders,
+                        TyKind::BoundVar(BoundVar::new(
+                            self.in_binders,
                             idx as usize + parent_params + self_params + list_params,
                         ))
+                        .intern(&Interner)
                     }
                     ImplTraitLoweringMode::Disallowed => {
                         // FIXME: report error
-                        Ty::Unknown
+                        TyKind::Unknown.intern(&Interner)
                     }
                 }
             }
-            TypeRef::Error => Ty::Unknown,
+            TypeRef::Error => TyKind::Unknown.intern(&Interner),
         };
         (ty, res)
     }
@@ -278,7 +284,7 @@ impl Ty {
     /// This is only for `generic_predicates_for_param`, where we can't just
     /// lower the self types of the predicates since that could lead to cycles.
     /// So we just check here if the `type_ref` resolves to a generic param, and which.
-    fn from_hir_only_param(ctx: &TyLoweringContext<'_>, type_ref: &TypeRef) -> Option<TypeParamId> {
+    fn lower_ty_only_param(&self, type_ref: &TypeRef) -> Option<TypeParamId> {
         let path = match type_ref {
             TypeRef::Path(path) => path,
             _ => return None,
@@ -290,7 +296,7 @@ impl Ty {
             return None;
         }
         let resolution =
-            match ctx.resolver.resolve_path_in_type_ns(ctx.db.upcast(), path.mod_path()) {
+            match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
                 Some((it, None)) => it,
                 _ => return None,
             };
@@ -301,8 +307,8 @@ impl Ty {
         }
     }
 
-    pub(crate) fn from_type_relative_path(
-        ctx: &TyLoweringContext<'_>,
+    pub(crate) fn lower_ty_relative_path(
+        &self,
         ty: Ty,
         // We need the original resolution to lower `Self::AssocTy` correctly
         res: Option<TypeNs>,
@@ -311,17 +317,17 @@ impl Ty {
         if remaining_segments.len() == 1 {
             // resolve unselected assoc types
             let segment = remaining_segments.first().unwrap();
-            (Ty::select_associated_type(ctx, res, segment), None)
+            (self.select_associated_type(res, segment), None)
         } else if remaining_segments.len() > 1 {
             // FIXME report error (ambiguous associated type)
-            (Ty::Unknown, None)
+            (TyKind::Unknown.intern(&Interner), None)
         } else {
             (ty, res)
         }
     }
 
-    pub(crate) fn from_partly_resolved_hir_path(
-        ctx: &TyLoweringContext<'_>,
+    pub(crate) fn lower_partly_resolved_path(
+        &self,
         resolution: TypeNs,
         resolved_segment: PathSegment<'_>,
         remaining_segments: PathSegments<'_>,
@@ -331,103 +337,109 @@ impl Ty {
             TypeNs::TraitId(trait_) => {
                 // if this is a bare dyn Trait, we'll directly put the required ^0 for the self type in there
                 let self_ty = if remaining_segments.len() == 0 {
-                    Some(Ty::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)))
+                    Some(
+                        TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
+                            .intern(&Interner),
+                    )
                 } else {
                     None
                 };
                 let trait_ref =
-                    TraitRef::from_resolved_path(ctx, trait_, resolved_segment, self_ty);
+                    self.lower_trait_ref_from_resolved_path(trait_, resolved_segment, self_ty);
                 let ty = if remaining_segments.len() == 1 {
                     let segment = remaining_segments.first().unwrap();
                     let found = associated_type_by_name_including_super_traits(
-                        ctx.db,
+                        self.db,
                         trait_ref,
                         &segment.name,
                     );
                     match found {
                         Some((super_trait_ref, associated_ty)) => {
                             // FIXME handle type parameters on the segment
-                            Ty::Alias(AliasTy::Projection(ProjectionTy {
-                                associated_ty,
+                            TyKind::Alias(AliasTy::Projection(ProjectionTy {
+                                associated_ty: to_assoc_type_id(associated_ty),
                                 parameters: super_trait_ref.substs,
                             }))
+                            .intern(&Interner)
                         }
                         None => {
                             // FIXME: report error (associated type not found)
-                            Ty::Unknown
+                            TyKind::Unknown.intern(&Interner)
                         }
                     }
                 } else if remaining_segments.len() > 1 {
                     // FIXME report error (ambiguous associated type)
-                    Ty::Unknown
+                    TyKind::Unknown.intern(&Interner)
                 } else {
-                    Ty::Dyn(Arc::new([GenericPredicate::Implemented(trait_ref)]))
+                    TyKind::Dyn(Arc::new([GenericPredicate::Implemented(trait_ref)]))
+                        .intern(&Interner)
                 };
                 return (ty, None);
             }
             TypeNs::GenericParam(param_id) => {
                 let generics = generics(
-                    ctx.db.upcast(),
-                    ctx.resolver.generic_def().expect("generics in scope"),
+                    self.db.upcast(),
+                    self.resolver.generic_def().expect("generics in scope"),
                 );
-                match ctx.type_param_mode {
-                    TypeParamLoweringMode::Placeholder => Ty::Placeholder(param_id),
+                match self.type_param_mode {
+                    TypeParamLoweringMode::Placeholder => {
+                        TyKind::Placeholder(to_placeholder_idx(self.db, param_id))
+                    }
                     TypeParamLoweringMode::Variable => {
                         let idx = generics.param_idx(param_id).expect("matching generics");
-                        Ty::BoundVar(BoundVar::new(ctx.in_binders, idx))
+                        TyKind::BoundVar(BoundVar::new(self.in_binders, idx))
                     }
                 }
+                .intern(&Interner)
             }
             TypeNs::SelfType(impl_id) => {
-                let generics = generics(ctx.db.upcast(), impl_id.into());
-                let substs = match ctx.type_param_mode {
+                let generics = generics(self.db.upcast(), impl_id.into());
+                let substs = match self.type_param_mode {
                     TypeParamLoweringMode::Placeholder => {
-                        Substs::type_params_for_generics(&generics)
+                        Substs::type_params_for_generics(self.db, &generics)
                     }
                     TypeParamLoweringMode::Variable => {
-                        Substs::bound_vars(&generics, ctx.in_binders)
+                        Substs::bound_vars(&generics, self.in_binders)
                     }
                 };
-                ctx.db.impl_self_ty(impl_id).subst(&substs)
+                self.db.impl_self_ty(impl_id).subst(&substs)
             }
             TypeNs::AdtSelfType(adt) => {
-                let generics = generics(ctx.db.upcast(), adt.into());
-                let substs = match ctx.type_param_mode {
+                let generics = generics(self.db.upcast(), adt.into());
+                let substs = match self.type_param_mode {
                     TypeParamLoweringMode::Placeholder => {
-                        Substs::type_params_for_generics(&generics)
+                        Substs::type_params_for_generics(self.db, &generics)
                     }
                     TypeParamLoweringMode::Variable => {
-                        Substs::bound_vars(&generics, ctx.in_binders)
+                        Substs::bound_vars(&generics, self.in_binders)
                     }
                 };
-                ctx.db.ty(adt.into()).subst(&substs)
+                self.db.ty(adt.into()).subst(&substs)
             }
 
-            TypeNs::AdtId(it) => {
-                Ty::from_hir_path_inner(ctx, resolved_segment, it.into(), infer_args)
-            }
+            TypeNs::AdtId(it) => self.lower_path_inner(resolved_segment, it.into(), infer_args),
             TypeNs::BuiltinType(it) => {
-                Ty::from_hir_path_inner(ctx, resolved_segment, it.into(), infer_args)
+                self.lower_path_inner(resolved_segment, it.into(), infer_args)
             }
             TypeNs::TypeAliasId(it) => {
-                Ty::from_hir_path_inner(ctx, resolved_segment, it.into(), infer_args)
+                self.lower_path_inner(resolved_segment, it.into(), infer_args)
             }
             // FIXME: report error
-            TypeNs::EnumVariantId(_) => return (Ty::Unknown, None),
+            TypeNs::EnumVariantId(_) => return (TyKind::Unknown.intern(&Interner), None),
         };
-        Ty::from_type_relative_path(ctx, ty, Some(resolution), remaining_segments)
+        self.lower_ty_relative_path(ty, Some(resolution), remaining_segments)
     }
 
-    pub(crate) fn from_hir_path(ctx: &TyLoweringContext<'_>, path: &Path) -> (Ty, Option<TypeNs>) {
+    pub(crate) fn lower_path(&self, path: &Path) -> (Ty, Option<TypeNs>) {
         // Resolve the path (in type namespace)
         if let Some(type_ref) = path.type_anchor() {
-            let (ty, res) = Ty::from_hir_ext(ctx, &type_ref);
-            return Ty::from_type_relative_path(ctx, ty, res, path.segments());
+            let (ty, res) = self.lower_ty_ext(&type_ref);
+            return self.lower_ty_relative_path(ty, res, path.segments());
         }
         let (resolution, remaining_index) =
-            match ctx.resolver.resolve_path_in_type_ns(ctx.db.upcast(), path.mod_path()) {
+            match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
                 Some(it) => it,
-                None => return (Ty::Unknown, None),
+                None => return (TyKind::Unknown.intern(&Interner), None),
             };
         let (resolved_segment, remaining_segments) = match remaining_index {
             None => (
@@ -436,31 +448,23 @@ impl Ty {
             ),
             Some(i) => (path.segments().get(i - 1).unwrap(), path.segments().skip(i)),
         };
-        Ty::from_partly_resolved_hir_path(
-            ctx,
-            resolution,
-            resolved_segment,
-            remaining_segments,
-            false,
-        )
+        self.lower_partly_resolved_path(resolution, resolved_segment, remaining_segments, false)
     }
 
-    fn select_associated_type(
-        ctx: &TyLoweringContext<'_>,
-        res: Option<TypeNs>,
-        segment: PathSegment<'_>,
-    ) -> Ty {
+    fn select_associated_type(&self, res: Option<TypeNs>, segment: PathSegment<'_>) -> Ty {
         if let Some(res) = res {
-            let ty =
-                associated_type_shorthand_candidates(ctx.db, res, move |name, t, associated_ty| {
+            let ty = associated_type_shorthand_candidates(
+                self.db,
+                res,
+                move |name, t, associated_ty| {
                     if name == segment.name {
-                        let substs = match ctx.type_param_mode {
+                        let substs = match self.type_param_mode {
                             TypeParamLoweringMode::Placeholder => {
                                 // if we're lowering to placeholders, we have to put
                                 // them in now
                                 let s = Substs::type_params(
-                                    ctx.db,
-                                    ctx.resolver.generic_def().expect(
+                                    self.db,
+                                    self.resolver.generic_def().expect(
                                         "there should be generics if there's a generic param",
                                     ),
                                 );
@@ -470,25 +474,29 @@ impl Ty {
                         };
                         // We need to shift in the bound vars, since
                         // associated_type_shorthand_candidates does not do that
-                        let substs = substs.shift_bound_vars(ctx.in_binders);
+                        let substs = substs.shift_bound_vars(self.in_binders);
                         // FIXME handle type parameters on the segment
-                        return Some(Ty::Alias(AliasTy::Projection(ProjectionTy {
-                            associated_ty,
-                            parameters: substs,
-                        })));
+                        return Some(
+                            TyKind::Alias(AliasTy::Projection(ProjectionTy {
+                                associated_ty: to_assoc_type_id(associated_ty),
+                                parameters: substs,
+                            }))
+                            .intern(&Interner),
+                        );
                     }
 
                     None
-                });
+                },
+            );
 
-            ty.unwrap_or(Ty::Unknown)
+            ty.unwrap_or(TyKind::Unknown.intern(&Interner))
         } else {
-            Ty::Unknown
+            TyKind::Unknown.intern(&Interner)
         }
     }
 
-    fn from_hir_path_inner(
-        ctx: &TyLoweringContext<'_>,
+    fn lower_path_inner(
+        &self,
         segment: PathSegment<'_>,
         typeable: TyDefId,
         infer_args: bool,
@@ -498,14 +506,14 @@ impl Ty {
             TyDefId::AdtId(it) => Some(it.into()),
             TyDefId::TypeAliasId(it) => Some(it.into()),
         };
-        let substs = substs_from_path_segment(ctx, segment, generic_def, infer_args);
-        ctx.db.ty(typeable).subst(&substs)
+        let substs = self.substs_from_path_segment(segment, generic_def, infer_args);
+        self.db.ty(typeable).subst(&substs)
     }
 
     /// Collect generic arguments from a path into a `Substs`. See also
     /// `create_substs_for_ast_path` and `def_to_ty` in rustc.
     pub(super) fn substs_from_path(
-        ctx: &TyLoweringContext<'_>,
+        &self,
         path: &Path,
         // Note that we don't call `db.value_type(resolved)` here,
         // `ValueTyDefId` is just a convenient way to pass generics and
@@ -535,169 +543,161 @@ impl Ty {
                 (segment, Some(var.parent.into()))
             }
         };
-        substs_from_path_segment(ctx, segment, generic_def, infer_args)
+        self.substs_from_path_segment(segment, generic_def, infer_args)
     }
-}
 
-fn substs_from_path_segment(
-    ctx: &TyLoweringContext<'_>,
-    segment: PathSegment<'_>,
-    def_generic: Option<GenericDefId>,
-    infer_args: bool,
-) -> Substs {
-    let mut substs = Vec::new();
-    let def_generics = def_generic.map(|def| generics(ctx.db.upcast(), def));
+    fn substs_from_path_segment(
+        &self,
+        segment: PathSegment<'_>,
+        def_generic: Option<GenericDefId>,
+        infer_args: bool,
+    ) -> Substs {
+        let mut substs = Vec::new();
+        let def_generics = def_generic.map(|def| generics(self.db.upcast(), def));
 
-    let (parent_params, self_params, type_params, impl_trait_params) =
-        def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
-    let total_len = parent_params + self_params + type_params + impl_trait_params;
+        let (parent_params, self_params, type_params, impl_trait_params) =
+            def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
+        let total_len = parent_params + self_params + type_params + impl_trait_params;
 
-    substs.extend(iter::repeat(Ty::Unknown).take(parent_params));
+        substs.extend(iter::repeat(TyKind::Unknown.intern(&Interner)).take(parent_params));
 
-    let mut had_explicit_type_args = false;
+        let mut had_explicit_type_args = false;
 
-    if let Some(generic_args) = &segment.args_and_bindings {
-        if !generic_args.has_self_type {
-            substs.extend(iter::repeat(Ty::Unknown).take(self_params));
-        }
-        let expected_num =
-            if generic_args.has_self_type { self_params + type_params } else { type_params };
-        let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
-        // if args are provided, it should be all of them, but we can't rely on that
-        for arg in generic_args
-            .args
-            .iter()
-            .filter(|arg| matches!(arg, GenericArg::Type(_)))
-            .skip(skip)
-            .take(expected_num)
-        {
-            match arg {
-                GenericArg::Type(type_ref) => {
-                    had_explicit_type_args = true;
-                    let ty = Ty::from_hir(ctx, type_ref);
-                    substs.push(ty);
+        if let Some(generic_args) = &segment.args_and_bindings {
+            if !generic_args.has_self_type {
+                substs.extend(iter::repeat(TyKind::Unknown.intern(&Interner)).take(self_params));
+            }
+            let expected_num =
+                if generic_args.has_self_type { self_params + type_params } else { type_params };
+            let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
+            // if args are provided, it should be all of them, but we can't rely on that
+            for arg in generic_args
+                .args
+                .iter()
+                .filter(|arg| matches!(arg, GenericArg::Type(_)))
+                .skip(skip)
+                .take(expected_num)
+            {
+                match arg {
+                    GenericArg::Type(type_ref) => {
+                        had_explicit_type_args = true;
+                        let ty = self.lower_ty(type_ref);
+                        substs.push(ty);
+                    }
+                    GenericArg::Lifetime(_) => {}
                 }
-                GenericArg::Lifetime(_) => {}
             }
         }
-    }
 
-    // handle defaults. In expression or pattern path segments without
-    // explicitly specified type arguments, missing type arguments are inferred
-    // (i.e. defaults aren't used).
-    if !infer_args || had_explicit_type_args {
-        if let Some(def_generic) = def_generic {
-            let defaults = ctx.db.generic_defaults(def_generic);
-            assert_eq!(total_len, defaults.len());
-
-            for default_ty in defaults.iter().skip(substs.len()) {
-                // each default can depend on the previous parameters
-                let substs_so_far = Substs(substs.clone().into());
-                substs.push(default_ty.clone().subst(&substs_so_far));
+        // handle defaults. In expression or pattern path segments without
+        // explicitly specified type arguments, missing type arguments are inferred
+        // (i.e. defaults aren't used).
+        if !infer_args || had_explicit_type_args {
+            if let Some(def_generic) = def_generic {
+                let defaults = self.db.generic_defaults(def_generic);
+                assert_eq!(total_len, defaults.len());
+
+                for default_ty in defaults.iter().skip(substs.len()) {
+                    // each default can depend on the previous parameters
+                    let substs_so_far = Substs(substs.clone().into());
+                    substs.push(default_ty.clone().subst(&substs_so_far));
+                }
             }
         }
-    }
 
-    // add placeholders for args that were not provided
-    // FIXME: emit diagnostics in contexts where this is not allowed
-    for _ in substs.len()..total_len {
-        substs.push(Ty::Unknown);
-    }
-    assert_eq!(substs.len(), total_len);
+        // add placeholders for args that were not provided
+        // FIXME: emit diagnostics in contexts where this is not allowed
+        for _ in substs.len()..total_len {
+            substs.push(TyKind::Unknown.intern(&Interner));
+        }
+        assert_eq!(substs.len(), total_len);
 
-    Substs(substs.into())
-}
+        Substs(substs.into())
+    }
 
-impl TraitRef {
-    fn from_path(
-        ctx: &TyLoweringContext<'_>,
+    fn lower_trait_ref_from_path(
+        &self,
         path: &Path,
         explicit_self_ty: Option<Ty>,
-    ) -> Option<Self> {
+    ) -> Option<TraitRef> {
         let resolved =
-            match ctx.resolver.resolve_path_in_type_ns_fully(ctx.db.upcast(), path.mod_path())? {
+            match self.resolver.resolve_path_in_type_ns_fully(self.db.upcast(), path.mod_path())? {
                 TypeNs::TraitId(tr) => tr,
                 _ => return None,
             };
         let segment = path.segments().last().expect("path should have at least one segment");
-        Some(TraitRef::from_resolved_path(ctx, resolved, segment, explicit_self_ty))
+        Some(self.lower_trait_ref_from_resolved_path(resolved, segment, explicit_self_ty))
     }
 
-    pub(crate) fn from_resolved_path(
-        ctx: &TyLoweringContext<'_>,
+    pub(crate) fn lower_trait_ref_from_resolved_path(
+        &self,
         resolved: TraitId,
         segment: PathSegment<'_>,
         explicit_self_ty: Option<Ty>,
-    ) -> Self {
-        let mut substs = TraitRef::substs_from_path(ctx, segment, resolved);
+    ) -> TraitRef {
+        let mut substs = self.trait_ref_substs_from_path(segment, resolved);
         if let Some(self_ty) = explicit_self_ty {
             make_mut_slice(&mut substs.0)[0] = self_ty;
         }
         TraitRef { trait_: resolved, substs }
     }
 
-    fn from_hir(
-        ctx: &TyLoweringContext<'_>,
+    fn lower_trait_ref(
+        &self,
         type_ref: &TypeRef,
         explicit_self_ty: Option<Ty>,
-    ) -> Option<Self> {
+    ) -> Option<TraitRef> {
         let path = match type_ref {
             TypeRef::Path(path) => path,
             _ => return None,
         };
-        TraitRef::from_path(ctx, path, explicit_self_ty)
+        self.lower_trait_ref_from_path(path, explicit_self_ty)
     }
 
-    fn substs_from_path(
-        ctx: &TyLoweringContext<'_>,
-        segment: PathSegment<'_>,
-        resolved: TraitId,
-    ) -> Substs {
-        substs_from_path_segment(ctx, segment, Some(resolved.into()), false)
+    fn trait_ref_substs_from_path(&self, segment: PathSegment<'_>, resolved: TraitId) -> Substs {
+        self.substs_from_path_segment(segment, Some(resolved.into()), false)
     }
-}
 
-impl GenericPredicate {
-    pub(crate) fn from_where_predicate<'a>(
-        ctx: &'a TyLoweringContext<'a>,
+    pub(crate) fn lower_where_predicate(
+        &'a self,
         where_predicate: &'a WherePredicate,
     ) -> impl Iterator<Item = GenericPredicate> + 'a {
         match where_predicate {
             WherePredicate::ForLifetime { target, bound, .. }
             | WherePredicate::TypeBound { target, bound } => {
                 let self_ty = match target {
-                    WherePredicateTypeTarget::TypeRef(type_ref) => Ty::from_hir(ctx, type_ref),
+                    WherePredicateTypeTarget::TypeRef(type_ref) => self.lower_ty(type_ref),
                     WherePredicateTypeTarget::TypeParam(param_id) => {
-                        let generic_def = ctx.resolver.generic_def().expect("generics in scope");
-                        let generics = generics(ctx.db.upcast(), generic_def);
+                        let generic_def = self.resolver.generic_def().expect("generics in scope");
+                        let generics = generics(self.db.upcast(), generic_def);
                         let param_id =
                             hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
-                        match ctx.type_param_mode {
-                            TypeParamLoweringMode::Placeholder => Ty::Placeholder(param_id),
+                        let placeholder = to_placeholder_idx(self.db, param_id);
+                        match self.type_param_mode {
+                            TypeParamLoweringMode::Placeholder => TyKind::Placeholder(placeholder),
                             TypeParamLoweringMode::Variable => {
                                 let idx = generics.param_idx(param_id).expect("matching generics");
-                                Ty::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, idx))
+                                TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, idx))
                             }
                         }
+                        .intern(&Interner)
                     }
                 };
-                GenericPredicate::from_type_bound(ctx, bound, self_ty)
-                    .collect::<Vec<_>>()
-                    .into_iter()
+                self.lower_type_bound(bound, self_ty).collect::<Vec<_>>().into_iter()
             }
             WherePredicate::Lifetime { .. } => vec![].into_iter(),
         }
     }
 
-    pub(crate) fn from_type_bound<'a>(
-        ctx: &'a TyLoweringContext<'a>,
+    pub(crate) fn lower_type_bound(
+        &'a self,
         bound: &'a TypeBound,
         self_ty: Ty,
     ) -> impl Iterator<Item = GenericPredicate> + 'a {
         let mut bindings = None;
         let trait_ref = match bound {
             TypeBound::Path(path) => {
-                bindings = TraitRef::from_path(ctx, path, Some(self_ty));
+                bindings = self.lower_trait_ref_from_path(path, Some(self_ty));
                 Some(
                     bindings.clone().map_or(GenericPredicate::Error, GenericPredicate::Implemented),
                 )
@@ -708,64 +708,62 @@ impl GenericPredicate {
         trait_ref.into_iter().chain(
             bindings
                 .into_iter()
-                .flat_map(move |tr| assoc_type_bindings_from_type_bound(ctx, bound, tr)),
+                .flat_map(move |tr| self.assoc_type_bindings_from_type_bound(bound, tr)),
         )
     }
-}
 
-fn assoc_type_bindings_from_type_bound<'a>(
-    ctx: &'a TyLoweringContext<'a>,
-    bound: &'a TypeBound,
-    trait_ref: TraitRef,
-) -> impl Iterator<Item = GenericPredicate> + 'a {
-    let last_segment = match bound {
-        TypeBound::Path(path) => path.segments().last(),
-        TypeBound::Error | TypeBound::Lifetime(_) => None,
-    };
-    last_segment
-        .into_iter()
-        .flat_map(|segment| segment.args_and_bindings.into_iter())
-        .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
-        .flat_map(move |binding| {
-            let found = associated_type_by_name_including_super_traits(
-                ctx.db,
-                trait_ref.clone(),
-                &binding.name,
-            );
-            let (super_trait_ref, associated_ty) = match found {
-                None => return SmallVec::<[GenericPredicate; 1]>::new(),
-                Some(t) => t,
-            };
-            let projection_ty = ProjectionTy { associated_ty, parameters: super_trait_ref.substs };
-            let mut preds = SmallVec::with_capacity(
-                binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
-            );
-            if let Some(type_ref) = &binding.type_ref {
-                let ty = Ty::from_hir(ctx, type_ref);
-                let projection_predicate =
-                    ProjectionPredicate { projection_ty: projection_ty.clone(), ty };
-                preds.push(GenericPredicate::Projection(projection_predicate));
-            }
-            for bound in &binding.bounds {
-                preds.extend(GenericPredicate::from_type_bound(
-                    ctx,
-                    bound,
-                    Ty::Alias(AliasTy::Projection(projection_ty.clone())),
-                ));
-            }
-            preds
-        })
-}
+    fn assoc_type_bindings_from_type_bound(
+        &'a self,
+        bound: &'a TypeBound,
+        trait_ref: TraitRef,
+    ) -> impl Iterator<Item = GenericPredicate> + 'a {
+        let last_segment = match bound {
+            TypeBound::Path(path) => path.segments().last(),
+            TypeBound::Error | TypeBound::Lifetime(_) => None,
+        };
+        last_segment
+            .into_iter()
+            .flat_map(|segment| segment.args_and_bindings.into_iter())
+            .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
+            .flat_map(move |binding| {
+                let found = associated_type_by_name_including_super_traits(
+                    self.db,
+                    trait_ref.clone(),
+                    &binding.name,
+                );
+                let (super_trait_ref, associated_ty) = match found {
+                    None => return SmallVec::<[GenericPredicate; 1]>::new(),
+                    Some(t) => t,
+                };
+                let projection_ty = ProjectionTy {
+                    associated_ty: to_assoc_type_id(associated_ty),
+                    parameters: super_trait_ref.substs,
+                };
+                let mut preds = SmallVec::with_capacity(
+                    binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
+                );
+                if let Some(type_ref) = &binding.type_ref {
+                    let ty = self.lower_ty(type_ref);
+                    let projection_predicate =
+                        ProjectionPredicate { projection_ty: projection_ty.clone(), ty };
+                    preds.push(GenericPredicate::Projection(projection_predicate));
+                }
+                for bound in &binding.bounds {
+                    preds.extend(self.lower_type_bound(
+                        bound,
+                        TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(&Interner),
+                    ));
+                }
+                preds
+            })
+    }
 
-impl ReturnTypeImplTrait {
-    fn from_hir(ctx: &TyLoweringContext, bounds: &[TypeBound]) -> Self {
+    fn lower_impl_trait(&self, bounds: &[TypeBound]) -> ReturnTypeImplTrait {
         cov_mark::hit!(lower_rpit);
-        let self_ty = Ty::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0));
-        let predicates = ctx.with_shifted_in(DebruijnIndex::ONE, |ctx| {
-            bounds
-                .iter()
-                .flat_map(|b| GenericPredicate::from_type_bound(ctx, b, self_ty.clone()))
-                .collect()
+        let self_ty =
+            TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
+        let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
+            bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone())).collect()
         });
         ReturnTypeImplTrait { bounds: Binders::new(1, predicates) }
     }
@@ -861,7 +859,7 @@ pub(crate) fn field_types_query(
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     for (field_id, field_data) in var_data.fields().iter() {
-        res.insert(field_id, Binders::new(generics.len(), Ty::from_hir(&ctx, &field_data.type_ref)))
+        res.insert(field_id, Binders::new(generics.len(), ctx.lower_ty(&field_data.type_ref)))
     }
     Arc::new(res)
 }
@@ -889,16 +887,13 @@ pub(crate) fn generic_predicates_for_param_query(
             WherePredicate::ForLifetime { target, .. }
             | WherePredicate::TypeBound { target, .. } => match target {
                 WherePredicateTypeTarget::TypeRef(type_ref) => {
-                    Ty::from_hir_only_param(&ctx, type_ref) == Some(param_id)
+                    ctx.lower_ty_only_param(type_ref) == Some(param_id)
                 }
                 WherePredicateTypeTarget::TypeParam(local_id) => *local_id == param_id.local_id,
             },
             WherePredicate::Lifetime { .. } => false,
         })
-        .flat_map(|pred| {
-            GenericPredicate::from_where_predicate(&ctx, pred)
-                .map(|p| Binders::new(generics.len(), p))
-        })
+        .flat_map(|pred| ctx.lower_where_predicate(pred).map(|p| Binders::new(generics.len(), p)))
         .collect()
 }
 
@@ -910,41 +905,55 @@ pub(crate) fn generic_predicates_for_param_recover(
     Arc::new([])
 }
 
-impl TraitEnvironment {
-    pub fn lower(db: &dyn HirDatabase, resolver: &Resolver) -> Arc<TraitEnvironment> {
-        let ctx = TyLoweringContext::new(db, &resolver)
-            .with_type_param_mode(TypeParamLoweringMode::Placeholder);
-        let mut predicates = resolver
-            .where_predicates_in_scope()
-            .flat_map(|pred| GenericPredicate::from_where_predicate(&ctx, pred))
-            .collect::<Vec<_>>();
-
-        if let Some(def) = resolver.generic_def() {
-            let container: Option<AssocContainerId> = match def {
-                // FIXME: is there a function for this?
-                GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container),
-                GenericDefId::AdtId(_) => None,
-                GenericDefId::TraitId(_) => None,
-                GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container),
-                GenericDefId::ImplId(_) => None,
-                GenericDefId::EnumVariantId(_) => None,
-                GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container),
-            };
-            if let Some(AssocContainerId::TraitId(trait_id)) = container {
-                // add `Self: Trait<T1, T2, ...>` to the environment in trait
-                // function default implementations (and hypothetical code
-                // inside consts or type aliases)
-                cov_mark::hit!(trait_self_implements_self);
-                let substs = Substs::type_params(db, trait_id);
-                let trait_ref = TraitRef { trait_: trait_id, substs };
-                let pred = GenericPredicate::Implemented(trait_ref);
-
-                predicates.push(pred);
+pub(crate) fn trait_environment_query(
+    db: &dyn HirDatabase,
+    def: GenericDefId,
+) -> Arc<TraitEnvironment> {
+    let resolver = def.resolver(db.upcast());
+    let ctx = TyLoweringContext::new(db, &resolver)
+        .with_type_param_mode(TypeParamLoweringMode::Placeholder);
+    let mut traits_in_scope = Vec::new();
+    let mut clauses = Vec::new();
+    for pred in resolver.where_predicates_in_scope() {
+        for pred in ctx.lower_where_predicate(pred) {
+            if pred.is_error() {
+                continue;
             }
+            if let GenericPredicate::Implemented(tr) = &pred {
+                traits_in_scope.push((tr.self_ty().clone(), tr.trait_));
+            }
+            let program_clause: chalk_ir::ProgramClause<Interner> =
+                pred.clone().to_chalk(db).cast(&Interner);
+            clauses.push(program_clause.into_from_env_clause(&Interner));
         }
+    }
 
-        Arc::new(TraitEnvironment { predicates })
+    let container: Option<AssocContainerId> = match def {
+        // FIXME: is there a function for this?
+        GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container),
+        GenericDefId::AdtId(_) => None,
+        GenericDefId::TraitId(_) => None,
+        GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container),
+        GenericDefId::ImplId(_) => None,
+        GenericDefId::EnumVariantId(_) => None,
+        GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container),
+    };
+    if let Some(AssocContainerId::TraitId(trait_id)) = container {
+        // add `Self: Trait<T1, T2, ...>` to the environment in trait
+        // function default implementations (and hypothetical code
+        // inside consts or type aliases)
+        cov_mark::hit!(trait_self_implements_self);
+        let substs = Substs::type_params(db, trait_id);
+        let trait_ref = TraitRef { trait_: trait_id, substs };
+        let pred = GenericPredicate::Implemented(trait_ref);
+        let program_clause: chalk_ir::ProgramClause<Interner> =
+            pred.clone().to_chalk(db).cast(&Interner);
+        clauses.push(program_clause.into_from_env_clause(&Interner));
     }
+
+    let env = chalk_ir::Environment::new(&Interner).add_clauses(&Interner, clauses);
+
+    Arc::new(TraitEnvironment { traits_from_clauses: traits_in_scope, env })
 }
 
 /// Resolve the where clause(s) of an item with generics.
@@ -958,10 +967,7 @@ pub(crate) fn generic_predicates_query(
     let generics = generics(db.upcast(), def);
     resolver
         .where_predicates_in_scope()
-        .flat_map(|pred| {
-            GenericPredicate::from_where_predicate(&ctx, pred)
-                .map(|p| Binders::new(generics.len(), p))
-        })
+        .flat_map(|pred| ctx.lower_where_predicate(pred).map(|p| Binders::new(generics.len(), p)))
         .collect()
 }
 
@@ -979,17 +985,18 @@ pub(crate) fn generic_defaults_query(
         .iter()
         .enumerate()
         .map(|(idx, (_, p))| {
-            let mut ty = p.default.as_ref().map_or(Ty::Unknown, |t| Ty::from_hir(&ctx, t));
+            let mut ty =
+                p.default.as_ref().map_or(TyKind::Unknown.intern(&Interner), |t| ctx.lower_ty(t));
 
             // Each default can only refer to previous parameters.
             ty.walk_mut_binders(
-                &mut |ty, binders| match ty {
-                    Ty::BoundVar(BoundVar { debruijn, index }) if *debruijn == binders => {
+                &mut |ty, binders| match &mut ty.0 {
+                    TyKind::BoundVar(BoundVar { debruijn, index }) if *debruijn == binders => {
                         if *index >= idx {
                             // type variable default referring to parameter coming
                             // after it. This is forbidden (FIXME: report
                             // diagnostic)
-                            *ty = Ty::Unknown;
+                            *ty = TyKind::Unknown.intern(&Interner);
                         }
                     }
                     _ => {}
@@ -1010,11 +1017,11 @@ fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
     let ctx_params = TyLoweringContext::new(db, &resolver)
         .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
         .with_type_param_mode(TypeParamLoweringMode::Variable);
-    let params = data.params.iter().map(|tr| Ty::from_hir(&ctx_params, tr)).collect::<Vec<_>>();
+    let params = data.params.iter().map(|tr| (&ctx_params).lower_ty(tr)).collect::<Vec<_>>();
     let ctx_ret = TyLoweringContext::new(db, &resolver)
         .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
         .with_type_param_mode(TypeParamLoweringMode::Variable);
-    let ret = Ty::from_hir(&ctx_ret, &data.ret_type);
+    let ret = (&ctx_ret).lower_ty(&data.ret_type);
     let generics = generics(db.upcast(), def.into());
     let num_binders = generics.len();
     Binders::new(num_binders, CallableSig::from_params_and_return(params, ret, data.is_varargs))
@@ -1025,7 +1032,10 @@ fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
 fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders<Ty> {
     let generics = generics(db.upcast(), def.into());
     let substs = Substs::bound_vars(&generics, DebruijnIndex::INNERMOST);
-    Binders::new(substs.len(), Ty::FnDef(def.into(), substs))
+    Binders::new(
+        substs.len(),
+        TyKind::FnDef(CallableDefId::FunctionId(def).to_chalk(db), substs).intern(&Interner),
+    )
 }
 
 /// Build the declared type of a const.
@@ -1036,7 +1046,7 @@ fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders<Ty> {
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
 
-    Binders::new(generics.len(), Ty::from_hir(&ctx, &data.type_ref))
+    Binders::new(generics.len(), ctx.lower_ty(&data.type_ref))
 }
 
 /// Build the declared type of a static.
@@ -1045,7 +1055,7 @@ fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders<Ty> {
     let resolver = def.resolver(db.upcast());
     let ctx = TyLoweringContext::new(db, &resolver);
 
-    Binders::new(0, Ty::from_hir(&ctx, &data.type_ref))
+    Binders::new(0, ctx.lower_ty(&data.type_ref))
 }
 
 fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
@@ -1054,8 +1064,7 @@ fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnS
     let resolver = def.resolver(db.upcast());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
-    let params =
-        fields.iter().map(|(_, field)| Ty::from_hir(&ctx, &field.type_ref)).collect::<Vec<_>>();
+    let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
     let ret = type_for_adt(db, def.into());
     Binders::new(ret.num_binders, CallableSig::from_params_and_return(params, ret.value, false))
 }
@@ -1068,7 +1077,10 @@ fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders<T
     }
     let generics = generics(db.upcast(), def.into());
     let substs = Substs::bound_vars(&generics, DebruijnIndex::INNERMOST);
-    Binders::new(substs.len(), Ty::FnDef(def.into(), substs))
+    Binders::new(
+        substs.len(),
+        TyKind::FnDef(CallableDefId::StructId(def).to_chalk(db), substs).intern(&Interner),
+    )
 }
 
 fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> PolyFnSig {
@@ -1078,8 +1090,7 @@ fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId)
     let resolver = def.parent.resolver(db.upcast());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
-    let params =
-        fields.iter().map(|(_, field)| Ty::from_hir(&ctx, &field.type_ref)).collect::<Vec<_>>();
+    let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
     let ret = type_for_adt(db, def.parent.into());
     Binders::new(ret.num_binders, CallableSig::from_params_and_return(params, ret.value, false))
 }
@@ -1093,7 +1104,10 @@ fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -
     }
     let generics = generics(db.upcast(), def.parent.into());
     let substs = Substs::bound_vars(&generics, DebruijnIndex::INNERMOST);
-    Binders::new(substs.len(), Ty::FnDef(def.into(), substs))
+    Binders::new(
+        substs.len(),
+        TyKind::FnDef(CallableDefId::EnumVariantId(def).to_chalk(db), substs).intern(&Interner),
+    )
 }
 
 fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders<Ty> {
@@ -1108,11 +1122,11 @@ fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     if db.type_alias_data(t).is_extern {
-        Binders::new(0, Ty::ForeignType(t))
+        Binders::new(0, TyKind::ForeignType(crate::to_foreign_def_id(t)).intern(&Interner))
     } else {
         let substs = Substs::bound_vars(&generics, DebruijnIndex::INNERMOST);
         let type_ref = &db.type_alias_data(t).type_ref;
-        let inner = Ty::from_hir(&ctx, type_ref.as_ref().unwrap_or(&TypeRef::Error));
+        let inner = ctx.lower_ty(type_ref.as_ref().unwrap_or(&TypeRef::Error));
         Binders::new(substs.len(), inner)
     }
 }
@@ -1184,7 +1198,7 @@ pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId)
         TyDefId::AdtId(it) => generics(db.upcast(), it.into()).len(),
         TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()).len(),
     };
-    Binders::new(num_binders, Ty::Unknown)
+    Binders::new(num_binders, TyKind::Unknown.intern(&Interner))
 }
 
 pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
@@ -1204,7 +1218,7 @@ pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binde
     let generics = generics(db.upcast(), impl_id.into());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
-    Binders::new(generics.len(), Ty::from_hir(&ctx, &impl_data.target_type))
+    Binders::new(generics.len(), ctx.lower_ty(&impl_data.target_type))
 }
 
 pub(crate) fn const_param_ty_query(db: &dyn HirDatabase, def: ConstParamId) -> Ty {
@@ -1213,7 +1227,7 @@ pub(crate) fn const_param_ty_query(db: &dyn HirDatabase, def: ConstParamId) -> T
     let resolver = def.parent.resolver(db.upcast());
     let ctx = TyLoweringContext::new(db, &resolver);
 
-    Ty::from_hir(&ctx, &data.ty)
+    ctx.lower_ty(&data.ty)
 }
 
 pub(crate) fn impl_self_ty_recover(
@@ -1222,7 +1236,7 @@ pub(crate) fn impl_self_ty_recover(
     impl_id: &ImplId,
 ) -> Binders<Ty> {
     let generics = generics(db.upcast(), (*impl_id).into());
-    Binders::new(generics.len(), Ty::Unknown)
+    Binders::new(generics.len(), TyKind::Unknown.intern(&Interner))
 }
 
 pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
@@ -1232,10 +1246,7 @@ pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     let self_ty = db.impl_self_ty(impl_id);
     let target_trait = impl_data.target_trait.as_ref()?;
-    Some(Binders::new(
-        self_ty.num_binders,
-        TraitRef::from_hir(&ctx, target_trait, Some(self_ty.value))?,
-    ))
+    Some(Binders::new(self_ty.num_binders, ctx.lower_trait_ref(target_trait, Some(self_ty.value))?))
 }
 
 pub(crate) fn return_type_impl_traits(
@@ -1248,7 +1259,7 @@ pub(crate) fn return_type_impl_traits(
     let ctx_ret = TyLoweringContext::new(db, &resolver)
         .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
         .with_type_param_mode(TypeParamLoweringMode::Variable);
-    let _ret = Ty::from_hir(&ctx_ret, &data.ret_type);
+    let _ret = (&ctx_ret).lower_ty(&data.ret_type);
     let generics = generics(db.upcast(), def.into());
     let num_binders = generics.len();
     let return_type_impl_traits =