Merge #8139

8139: Align `Canonical` and `InEnvironment` with the Chalk versions r=flodiebold a=flodiebold



Co-authored-by: Florian Diebold <[email protected]>

11 files changed, 194 insertions, 179 deletions

diff --git a/crates/hir/src/display.rs b/crates/hir/src/display.rs
index 9f6d7be48..97a78ca25 100644
--- a/crates/hir/src/display.rs
+++ b/crates/hir/src/display.rs
@@ -217,7 +217,7 @@ impl HirDisplay for Variant {
 
 impl HirDisplay for Type {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
-        self.ty.value.hir_fmt(f)
+        self.ty.hir_fmt(f)
     }
 }
 
diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index a325b6691..30b96d7e2 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -56,9 +56,9 @@ use hir_ty::{
     primitive::UintTy,
     to_assoc_type_id,
     traits::{FnTrait, Solution, SolutionVariables},
-    AliasEq, AliasTy, BoundVar, CallableDefId, CallableSig, Canonical, Cast, DebruijnIndex,
-    InEnvironment, Interner, ProjectionTy, QuantifiedWhereClause, Scalar, Substitution, Ty,
-    TyDefId, TyKind, TyVariableKind, WhereClause,
+    AliasEq, AliasTy, BoundVar, CallableDefId, CallableSig, Canonical, CanonicalVarKinds, Cast,
+    DebruijnIndex, InEnvironment, Interner, ProjectionTy, QuantifiedWhereClause, Scalar,
+    Substitution, TraitEnvironment, Ty, TyDefId, TyKind, TyVariableKind, WhereClause,
 };
 use itertools::Itertools;
 use rustc_hash::FxHashSet;
@@ -851,13 +851,7 @@ impl Function {
             .iter()
             .enumerate()
             .map(|(idx, type_ref)| {
-                let ty = Type {
-                    krate,
-                    ty: InEnvironment {
-                        value: ctx.lower_ty(type_ref),
-                        environment: environment.clone(),
-                    },
-                };
+                let ty = Type { krate, env: environment.clone(), ty: ctx.lower_ty(type_ref) };
                 Param { func: self, ty, idx }
             })
             .collect()
@@ -1540,8 +1534,8 @@ impl Impl {
         inherent.all_impls().chain(trait_.all_impls()).map(Self::from).collect()
     }
 
-    pub fn all_for_type(db: &dyn HirDatabase, Type { krate, ty }: Type) -> Vec<Impl> {
-        let def_crates = match ty.value.def_crates(db, krate) {
+    pub fn all_for_type(db: &dyn HirDatabase, Type { krate, ty, .. }: Type) -> Vec<Impl> {
+        let def_crates = match ty.def_crates(db, krate) {
             Some(def_crates) => def_crates,
             None => return Vec::new(),
         };
@@ -1549,14 +1543,14 @@ impl Impl {
         let filter = |impl_def: &Impl| {
             let target_ty = impl_def.target_ty(db);
             let rref = target_ty.remove_ref();
-            ty.value.equals_ctor(rref.as_ref().map_or(&target_ty.ty.value, |it| &it.ty.value))
+            ty.equals_ctor(rref.as_ref().map_or(&target_ty.ty, |it| &it.ty))
         };
 
         let mut all = Vec::new();
         def_crates.iter().for_each(|&id| {
             all.extend(db.inherent_impls_in_crate(id).all_impls().map(Self::from).filter(filter))
         });
-        let fp = TyFingerprint::for_impl(&ty.value);
+        let fp = TyFingerprint::for_impl(&ty);
         for id in def_crates
             .iter()
             .flat_map(|&id| Crate { id }.transitive_reverse_dependencies(db))
@@ -1643,7 +1637,8 @@ impl Impl {
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct Type {
     krate: CrateId,
-    ty: InEnvironment<Ty>,
+    env: Arc<TraitEnvironment>,
+    ty: Ty,
 }
 
 impl Type {
@@ -1663,14 +1658,14 @@ impl Type {
     ) -> Type {
         let environment =
             resolver.generic_def().map_or_else(Default::default, |d| db.trait_environment(d));
-        Type { krate, ty: InEnvironment { value: ty, environment } }
+        Type { krate, env: environment, ty }
     }
 
     fn new(db: &dyn HirDatabase, krate: CrateId, lexical_env: impl HasResolver, ty: Ty) -> Type {
         let resolver = lexical_env.resolver(db.upcast());
         let environment =
             resolver.generic_def().map_or_else(Default::default, |d| db.trait_environment(d));
-        Type { krate, ty: InEnvironment { value: ty, environment } }
+        Type { krate, env: environment, ty }
     }
 
     fn from_def(
@@ -1684,29 +1679,29 @@ impl Type {
     }
 
     pub fn is_unit(&self) -> bool {
-        matches!(self.ty.value.interned(&Interner), TyKind::Tuple(0, ..))
+        matches!(self.ty.interned(&Interner), TyKind::Tuple(0, ..))
     }
     pub fn is_bool(&self) -> bool {
-        matches!(self.ty.value.interned(&Interner), TyKind::Scalar(Scalar::Bool))
+        matches!(self.ty.interned(&Interner), TyKind::Scalar(Scalar::Bool))
     }
 
     pub fn is_mutable_reference(&self) -> bool {
-        matches!(self.ty.value.interned(&Interner), TyKind::Ref(hir_ty::Mutability::Mut, ..))
+        matches!(self.ty.interned(&Interner), TyKind::Ref(hir_ty::Mutability::Mut, ..))
     }
 
     pub fn is_usize(&self) -> bool {
-        matches!(self.ty.value.interned(&Interner), TyKind::Scalar(Scalar::Uint(UintTy::Usize)))
+        matches!(self.ty.interned(&Interner), TyKind::Scalar(Scalar::Uint(UintTy::Usize)))
     }
 
     pub fn remove_ref(&self) -> Option<Type> {
-        match &self.ty.value.interned(&Interner) {
+        match &self.ty.interned(&Interner) {
             TyKind::Ref(.., ty) => Some(self.derived(ty.clone())),
             _ => None,
         }
     }
 
     pub fn is_unknown(&self) -> bool {
-        self.ty.value.is_unknown()
+        self.ty.is_unknown()
     }
 
     /// Checks that particular type `ty` implements `std::future::Future`.
@@ -1723,11 +1718,12 @@ impl Type {
             None => return false,
         };
 
-        let canonical_ty = Canonical { value: self.ty.value.clone(), kinds: Arc::new([]) };
+        let canonical_ty =
+            Canonical { value: self.ty.clone(), binders: CanonicalVarKinds::empty(&Interner) };
         method_resolution::implements_trait(
             &canonical_ty,
             db,
-            self.ty.environment.clone(),
+            self.env.clone(),
             krate,
             std_future_trait,
         )
@@ -1745,11 +1741,12 @@ impl Type {
             None => return false,
         };
 
-        let canonical_ty = Canonical { value: self.ty.value.clone(), kinds: Arc::new([]) };
+        let canonical_ty =
+            Canonical { value: self.ty.clone(), binders: CanonicalVarKinds::empty(&Interner) };
         method_resolution::implements_trait_unique(
             &canonical_ty,
             db,
-            self.ty.environment.clone(),
+            self.env.clone(),
             krate,
             fnonce_trait,
         )
@@ -1759,17 +1756,14 @@ impl Type {
         let trait_ref = hir_ty::TraitRef {
             trait_id: hir_ty::to_chalk_trait_id(trait_.id),
             substitution: Substitution::build_for_def(db, trait_.id)
-                .push(self.ty.value.clone())
-                .fill(args.iter().map(|t| t.ty.value.clone()))
+                .push(self.ty.clone())
+                .fill(args.iter().map(|t| t.ty.clone()))
                 .build(),
         };
 
         let goal = Canonical {
-            value: hir_ty::InEnvironment::new(
-                self.ty.environment.clone(),
-                trait_ref.cast(&Interner),
-            ),
-            kinds: Arc::new([]),
+            value: hir_ty::InEnvironment::new(self.env.env.clone(), trait_ref.cast(&Interner)),
+            binders: CanonicalVarKinds::empty(&Interner),
         };
 
         db.trait_solve(self.krate, goal).is_some()
@@ -1783,12 +1777,12 @@ impl Type {
         alias: TypeAlias,
     ) -> Option<Type> {
         let subst = Substitution::build_for_def(db, trait_.id)
-            .push(self.ty.value.clone())
-            .fill(args.iter().map(|t| t.ty.value.clone()))
+            .push(self.ty.clone())
+            .fill(args.iter().map(|t| t.ty.clone()))
             .build();
-        let goal = Canonical {
-            value: InEnvironment::new(
-                self.ty.environment.clone(),
+        let goal = Canonical::new(
+            InEnvironment::new(
+                self.env.env.clone(),
                 AliasEq {
                     alias: AliasTy::Projection(ProjectionTy {
                         associated_ty_id: to_assoc_type_id(alias.id),
@@ -1799,8 +1793,8 @@ impl Type {
                 }
                 .cast(&Interner),
             ),
-            kinds: Arc::new([TyVariableKind::General]),
-        };
+            [TyVariableKind::General].iter().copied(),
+        );
 
         match db.trait_solve(self.krate, goal)? {
             Solution::Unique(SolutionVariables(subst)) => {
@@ -1820,22 +1814,22 @@ impl Type {
     }
 
     pub fn as_callable(&self, db: &dyn HirDatabase) -> Option<Callable> {
-        let def = self.ty.value.callable_def(db);
+        let def = self.ty.callable_def(db);
 
-        let sig = self.ty.value.callable_sig(db)?;
+        let sig = self.ty.callable_sig(db)?;
         Some(Callable { ty: self.clone(), sig, def, is_bound_method: false })
     }
 
     pub fn is_closure(&self) -> bool {
-        matches!(&self.ty.value.interned(&Interner), TyKind::Closure { .. })
+        matches!(&self.ty.interned(&Interner), TyKind::Closure { .. })
     }
 
     pub fn is_fn(&self) -> bool {
-        matches!(&self.ty.value.interned(&Interner), TyKind::FnDef(..) | TyKind::Function { .. })
+        matches!(&self.ty.interned(&Interner), TyKind::FnDef(..) | TyKind::Function { .. })
     }
 
     pub fn is_packed(&self, db: &dyn HirDatabase) -> bool {
-        let adt_id = match self.ty.value.interned(&Interner) {
+        let adt_id = match self.ty.interned(&Interner) {
             &TyKind::Adt(hir_ty::AdtId(adt_id), ..) => adt_id,
             _ => return false,
         };
@@ -1848,11 +1842,11 @@ impl Type {
     }
 
     pub fn is_raw_ptr(&self) -> bool {
-        matches!(&self.ty.value.interned(&Interner), TyKind::Raw(..))
+        matches!(&self.ty.interned(&Interner), TyKind::Raw(..))
     }
 
     pub fn contains_unknown(&self) -> bool {
-        return go(&self.ty.value);
+        return go(&self.ty);
 
         fn go(ty: &Ty) -> bool {
             match ty.interned(&Interner) {
@@ -1884,7 +1878,7 @@ impl Type {
     }
 
     pub fn fields(&self, db: &dyn HirDatabase) -> Vec<(Field, Type)> {
-        let (variant_id, substs) = match self.ty.value.interned(&Interner) {
+        let (variant_id, substs) = match self.ty.interned(&Interner) {
             &TyKind::Adt(hir_ty::AdtId(AdtId::StructId(s)), ref substs) => (s.into(), substs),
             &TyKind::Adt(hir_ty::AdtId(AdtId::UnionId(u)), ref substs) => (u.into(), substs),
             _ => return Vec::new(),
@@ -1901,7 +1895,7 @@ impl Type {
     }
 
     pub fn tuple_fields(&self, _db: &dyn HirDatabase) -> Vec<Type> {
-        if let TyKind::Tuple(_, substs) = &self.ty.value.interned(&Interner) {
+        if let TyKind::Tuple(_, substs) = &self.ty.interned(&Interner) {
             substs.iter().map(|ty| self.derived(ty.clone())).collect()
         } else {
             Vec::new()
@@ -1911,9 +1905,10 @@ impl Type {
     pub fn autoderef<'a>(&'a self, db: &'a dyn HirDatabase) -> impl Iterator<Item = Type> + 'a {
         // There should be no inference vars in types passed here
         // FIXME check that?
-        let canonical = Canonical { value: self.ty.value.clone(), kinds: Arc::new([]) };
-        let environment = self.ty.environment.clone();
-        let ty = InEnvironment { value: canonical, environment };
+        let canonical =
+            Canonical { value: self.ty.clone(), binders: CanonicalVarKinds::empty(&Interner) };
+        let environment = self.env.env.clone();
+        let ty = InEnvironment { goal: canonical, environment };
         autoderef(db, Some(self.krate), ty)
             .map(|canonical| canonical.value)
             .map(move |ty| self.derived(ty))
@@ -1927,10 +1922,10 @@ impl Type {
         krate: Crate,
         mut callback: impl FnMut(AssocItem) -> Option<T>,
     ) -> Option<T> {
-        for krate in self.ty.value.def_crates(db, krate.id)? {
+        for krate in self.ty.def_crates(db, krate.id)? {
             let impls = db.inherent_impls_in_crate(krate);
 
-            for impl_def in impls.for_self_ty(&self.ty.value) {
+            for impl_def in impls.for_self_ty(&self.ty) {
                 for &item in db.impl_data(*impl_def).items.iter() {
                     if let Some(result) = callback(item.into()) {
                         return Some(result);
@@ -1943,7 +1938,6 @@ impl Type {
 
     pub fn type_parameters(&self) -> impl Iterator<Item = Type> + '_ {
         self.ty
-            .value
             .strip_references()
             .substs()
             .into_iter()
@@ -1962,9 +1956,10 @@ impl Type {
         // There should be no inference vars in types passed here
         // FIXME check that?
         // FIXME replace Unknown by bound vars here
-        let canonical = Canonical { value: self.ty.value.clone(), kinds: Arc::new([]) };
+        let canonical =
+            Canonical { value: self.ty.clone(), binders: CanonicalVarKinds::empty(&Interner) };
 
-        let env = self.ty.environment.clone();
+        let env = self.env.clone();
         let krate = krate.id;
 
         method_resolution::iterate_method_candidates(
@@ -1993,9 +1988,10 @@ impl Type {
         // There should be no inference vars in types passed here
         // FIXME check that?
         // FIXME replace Unknown by bound vars here
-        let canonical = Canonical { value: self.ty.value.clone(), kinds: Arc::new([]) };
+        let canonical =
+            Canonical { value: self.ty.clone(), binders: CanonicalVarKinds::empty(&Interner) };
 
-        let env = self.ty.environment.clone();
+        let env = self.env.clone();
         let krate = krate.id;
 
         method_resolution::iterate_method_candidates(
@@ -2011,16 +2007,16 @@ impl Type {
     }
 
     pub fn as_adt(&self) -> Option<Adt> {
-        let (adt, _subst) = self.ty.value.as_adt()?;
+        let (adt, _subst) = self.ty.as_adt()?;
         Some(adt.into())
     }
 
     pub fn as_dyn_trait(&self) -> Option<Trait> {
-        self.ty.value.dyn_trait().map(Into::into)
+        self.ty.dyn_trait().map(Into::into)
     }
 
     pub fn as_impl_traits(&self, db: &dyn HirDatabase) -> Option<Vec<Trait>> {
-        self.ty.value.impl_trait_bounds(db).map(|it| {
+        self.ty.impl_trait_bounds(db).map(|it| {
             it.into_iter()
                 .filter_map(|pred| match pred.skip_binders() {
                     hir_ty::WhereClause::Implemented(trait_ref) => {
@@ -2033,14 +2029,11 @@ impl Type {
     }
 
     pub fn as_associated_type_parent_trait(&self, db: &dyn HirDatabase) -> Option<Trait> {
-        self.ty.value.associated_type_parent_trait(db).map(Into::into)
+        self.ty.associated_type_parent_trait(db).map(Into::into)
     }
 
     fn derived(&self, ty: Ty) -> Type {
-        Type {
-            krate: self.krate,
-            ty: InEnvironment { value: ty, environment: self.ty.environment.clone() },
-        }
+        Type { krate: self.krate, env: self.env.clone(), ty }
     }
 
     pub fn walk(&self, db: &dyn HirDatabase, mut cb: impl FnMut(Type)) {
@@ -2079,7 +2072,7 @@ impl Type {
         }
 
         fn walk_type(db: &dyn HirDatabase, type_: &Type, cb: &mut impl FnMut(Type)) {
-            let ty = type_.ty.value.strip_references();
+            let ty = type_.ty.strip_references();
             match ty.interned(&Interner) {
                 TyKind::Adt(..) => {
                     cb(type_.derived(ty.clone()));
diff --git a/crates/hir_ty/src/autoderef.rs b/crates/hir_ty/src/autoderef.rs
index 23ab042c1..dc5fc759a 100644
--- a/crates/hir_ty/src/autoderef.rs
+++ b/crates/hir_ty/src/autoderef.rs
@@ -16,8 +16,8 @@ use crate::{
     to_assoc_type_id, to_chalk_trait_id,
     traits::{InEnvironment, Solution},
     utils::generics,
-    AliasEq, AliasTy, BoundVar, Canonical, DebruijnIndex, Interner, ProjectionTy, Substitution,
-    TraitRef, Ty, TyKind,
+    AliasEq, AliasTy, BoundVar, Canonical, CanonicalVarKinds, DebruijnIndex, Interner,
+    ProjectionTy, Substitution, TraitRef, Ty, TyKind,
 };
 
 const AUTODEREF_RECURSION_LIMIT: usize = 10;
@@ -27,9 +27,9 @@ pub fn autoderef<'a>(
     krate: Option<CrateId>,
     ty: InEnvironment<Canonical<Ty>>,
 ) -> impl Iterator<Item = Canonical<Ty>> + 'a {
-    let InEnvironment { value: ty, environment } = ty;
+    let InEnvironment { goal: ty, environment } = ty;
     successors(Some(ty), move |ty| {
-        deref(db, krate?, InEnvironment { value: ty, environment: environment.clone() })
+        deref(db, krate?, InEnvironment { goal: ty, environment: environment.clone() })
     })
     .take(AUTODEREF_RECURSION_LIMIT)
 }
@@ -39,8 +39,8 @@ pub(crate) fn deref(
     krate: CrateId,
     ty: InEnvironment<&Canonical<Ty>>,
 ) -> Option<Canonical<Ty>> {
-    if let Some(derefed) = ty.value.value.builtin_deref() {
-        Some(Canonical { value: derefed, kinds: ty.value.kinds.clone() })
+    if let Some(derefed) = ty.goal.value.builtin_deref() {
+        Some(Canonical { value: derefed, binders: ty.goal.binders.clone() })
     } else {
         deref_by_trait(db, krate, ty)
     }
@@ -67,15 +67,15 @@ fn deref_by_trait(
     // FIXME make the Canonical / bound var handling nicer
 
     let parameters =
-        Substitution::build_for_generics(&generic_params).push(ty.value.value.clone()).build();
+        Substitution::build_for_generics(&generic_params).push(ty.goal.value.clone()).build();
 
     // Check that the type implements Deref at all
     let trait_ref =
         TraitRef { trait_id: to_chalk_trait_id(deref_trait), substitution: parameters.clone() };
     let implements_goal = Canonical {
-        kinds: ty.value.kinds.clone(),
+        binders: ty.goal.binders.clone(),
         value: InEnvironment {
-            value: trait_ref.cast(&Interner),
+            goal: trait_ref.cast(&Interner),
             environment: ty.environment.clone(),
         },
     };
@@ -89,18 +89,27 @@ fn deref_by_trait(
             associated_ty_id: to_assoc_type_id(target),
             substitution: parameters,
         }),
-        ty: TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, ty.value.kinds.len()))
-            .intern(&Interner),
+        ty: TyKind::BoundVar(BoundVar::new(
+            DebruijnIndex::INNERMOST,
+            ty.goal.binders.len(&Interner),
+        ))
+        .intern(&Interner),
     };
 
     let obligation = projection.cast(&Interner);
 
-    let in_env = InEnvironment { value: obligation, environment: ty.environment };
-
-    let canonical = Canonical::new(
-        in_env,
-        ty.value.kinds.iter().copied().chain(Some(chalk_ir::TyVariableKind::General)),
-    );
+    let in_env = InEnvironment { goal: obligation, environment: ty.environment };
+
+    let canonical = Canonical {
+        value: in_env,
+        binders: CanonicalVarKinds::from_iter(
+            &Interner,
+            ty.goal.binders.iter(&Interner).cloned().chain(Some(chalk_ir::WithKind::new(
+                chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
+                chalk_ir::UniverseIndex::ROOT,
+            ))),
+        ),
+    };
 
     let solution = db.trait_solve(krate, canonical)?;
 
@@ -121,21 +130,21 @@ fn deref_by_trait(
             // assumptions will be broken. We would need to properly introduce
             // new variables in that case
 
-            for i in 1..vars.0.kinds.len() {
+            for i in 1..vars.0.binders.len(&Interner) {
                 if vars.0.value[i - 1].interned(&Interner)
                     != &TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, i - 1))
                 {
-                    warn!("complex solution for derefing {:?}: {:?}, ignoring", ty.value, solution);
+                    warn!("complex solution for derefing {:?}: {:?}, ignoring", ty.goal, solution);
                     return None;
                 }
             }
             Some(Canonical {
                 value: vars.0.value[vars.0.value.len() - 1].clone(),
-                kinds: vars.0.kinds.clone(),
+                binders: vars.0.binders.clone(),
             })
         }
         Solution::Ambig(_) => {
-            info!("Ambiguous solution for derefing {:?}: {:?}", ty.value, solution);
+            info!("Ambiguous solution for derefing {:?}: {:?}", ty.goal, solution);
             None
         }
     }
diff --git a/crates/hir_ty/src/infer.rs b/crates/hir_ty/src/infer.rs
index b9e434c78..8f9cf7480 100644
--- a/crates/hir_ty/src/infer.rs
+++ b/crates/hir_ty/src/infer.rs
@@ -331,7 +331,7 @@ impl<'a> InferenceContext<'a> {
     fn resolve_obligations_as_possible(&mut self) {
         let obligations = mem::replace(&mut self.obligations, Vec::new());
         for obligation in obligations {
-            let in_env = InEnvironment::new(self.trait_env.clone(), obligation.clone());
+            let in_env = InEnvironment::new(self.trait_env.env.clone(), obligation.clone());
             let canonicalized = self.canonicalizer().canonicalize_obligation(in_env);
             let solution =
                 self.db.trait_solve(self.resolver.krate().unwrap(), canonicalized.value.clone());
diff --git a/crates/hir_ty/src/infer/coerce.rs b/crates/hir_ty/src/infer/coerce.rs
index 07eb96573..9c62932b1 100644
--- a/crates/hir_ty/src/infer/coerce.rs
+++ b/crates/hir_ty/src/infer/coerce.rs
@@ -142,7 +142,7 @@ impl<'a> InferenceContext<'a> {
             .build();
         let trait_ref =
             TraitRef { trait_id: to_chalk_trait_id(coerce_unsized_trait), substitution: substs };
-        let goal = InEnvironment::new(self.trait_env.clone(), trait_ref.cast(&Interner));
+        let goal = InEnvironment::new(self.trait_env.env.clone(), trait_ref.cast(&Interner));
 
         let canonicalizer = self.canonicalizer();
         let canonicalized = canonicalizer.canonicalize_obligation(goal);
@@ -170,8 +170,8 @@ impl<'a> InferenceContext<'a> {
             self.db,
             self.resolver.krate(),
             InEnvironment {
-                value: canonicalized.value.clone(),
-                environment: self.trait_env.clone(),
+                goal: canonicalized.value.clone(),
+                environment: self.trait_env.env.clone(),
             },
         ) {
             let derefed_ty = canonicalized.decanonicalize_ty(derefed_ty.value);
diff --git a/crates/hir_ty/src/infer/expr.rs b/crates/hir_ty/src/infer/expr.rs
index 05cbde4e3..19249973c 100644
--- a/crates/hir_ty/src/infer/expr.rs
+++ b/crates/hir_ty/src/infer/expr.rs
@@ -90,12 +90,12 @@ impl<'a> InferenceContext<'a> {
         let substs =
             Substitution::build_for_generics(&generic_params).push(ty.clone()).push(arg_ty).build();
 
-        let trait_env = Arc::clone(&self.trait_env);
+        let trait_env = self.trait_env.env.clone();
         let implements_fn_trait: DomainGoal =
             TraitRef { trait_id: to_chalk_trait_id(fn_once_trait), substitution: substs.clone() }
                 .cast(&Interner);
         let goal = self.canonicalizer().canonicalize_obligation(InEnvironment {
-            value: implements_fn_trait.clone(),
+            goal: implements_fn_trait.clone(),
             environment: trait_env,
         });
         if self.db.trait_solve(krate, goal.value).is_some() {
@@ -299,8 +299,8 @@ impl<'a> InferenceContext<'a> {
                     self.db,
                     self.resolver.krate(),
                     InEnvironment {
-                        value: canonicalized.value.clone(),
-                        environment: self.trait_env.clone(),
+                        goal: canonicalized.value.clone(),
+                        environment: self.trait_env.env.clone(),
                     },
                 );
                 let (param_tys, ret_ty): (Vec<Ty>, Ty) = derefs
@@ -438,8 +438,8 @@ impl<'a> InferenceContext<'a> {
                     self.db,
                     self.resolver.krate(),
                     InEnvironment {
-                        value: canonicalized.value.clone(),
-                        environment: self.trait_env.clone(),
+                        goal: canonicalized.value.clone(),
+                        environment: self.trait_env.env.clone(),
                     },
                 )
                 .find_map(|derefed_ty| {
@@ -538,8 +538,8 @@ impl<'a> InferenceContext<'a> {
                                 self.db,
                                 krate,
                                 InEnvironment {
-                                    value: &canonicalized.value,
-                                    environment: self.trait_env.clone(),
+                                    goal: &canonicalized.value,
+                                    environment: self.trait_env.env.clone(),
                                 },
                             ) {
                                 Some(derefed_ty) => {
diff --git a/crates/hir_ty/src/infer/unify.rs b/crates/hir_ty/src/infer/unify.rs
index 35b0a2059..75250a369 100644
--- a/crates/hir_ty/src/infer/unify.rs
+++ b/crates/hir_ty/src/infer/unify.rs
@@ -2,13 +2,13 @@
 
 use std::borrow::Cow;
 
-use chalk_ir::{FloatTy, IntTy, TyVariableKind};
+use chalk_ir::{FloatTy, IntTy, TyVariableKind, UniverseIndex, VariableKind};
 use ena::unify::{InPlaceUnificationTable, NoError, UnifyKey, UnifyValue};
 
 use super::{DomainGoal, InferenceContext};
 use crate::{
-    AliasEq, AliasTy, BoundVar, Canonical, DebruijnIndex, FnPointer, InEnvironment, InferenceVar,
-    Interner, Scalar, Substitution, Ty, TyKind, TypeWalk, WhereClause,
+    AliasEq, AliasTy, BoundVar, Canonical, CanonicalVarKinds, DebruijnIndex, FnPointer,
+    InEnvironment, InferenceVar, Interner, Scalar, Substitution, Ty, TyKind, TypeWalk, WhereClause,
 };
 
 impl<'a> InferenceContext<'a> {
@@ -76,8 +76,17 @@ impl<'a, 'b> Canonicalizer<'a, 'b> {
     }
 
     fn into_canonicalized<T>(self, result: T) -> Canonicalized<T> {
-        let kinds = self.free_vars.iter().map(|&(_, k)| k).collect();
-        Canonicalized { value: Canonical { value: result, kinds }, free_vars: self.free_vars }
+        let kinds = self
+            .free_vars
+            .iter()
+            .map(|&(_, k)| chalk_ir::WithKind::new(VariableKind::Ty(k), UniverseIndex::ROOT));
+        Canonicalized {
+            value: Canonical {
+                value: result,
+                binders: CanonicalVarKinds::from_iter(&Interner, kinds),
+            },
+            free_vars: self.free_vars,
+        }
     }
 
     pub(crate) fn canonicalize_ty(mut self, ty: Ty) -> Canonicalized<Ty> {
@@ -89,15 +98,12 @@ impl<'a, 'b> Canonicalizer<'a, 'b> {
         mut self,
         obligation: InEnvironment<DomainGoal>,
     ) -> Canonicalized<InEnvironment<DomainGoal>> {
-        let result = match obligation.value {
+        let result = match obligation.goal {
             DomainGoal::Holds(wc) => {
                 DomainGoal::Holds(self.do_canonicalize(wc, DebruijnIndex::INNERMOST))
             }
         };
-        self.into_canonicalized(InEnvironment {
-            value: result,
-            environment: obligation.environment,
-        })
+        self.into_canonicalized(InEnvironment { goal: result, environment: obligation.environment })
     }
 }
 
@@ -125,12 +131,19 @@ impl<T> Canonicalized<T> {
         // the solution may contain new variables, which we need to convert to new inference vars
         let new_vars = Substitution(
             solution
-                .kinds
-                .iter()
-                .map(|k| match k {
-                    TyVariableKind::General => ctx.table.new_type_var(),
-                    TyVariableKind::Integer => ctx.table.new_integer_var(),
-                    TyVariableKind::Float => ctx.table.new_float_var(),
+                .binders
+                .iter(&Interner)
+                .map(|k| match k.kind {
+                    VariableKind::Ty(TyVariableKind::General) => ctx.table.new_type_var(),
+                    VariableKind::Ty(TyVariableKind::Integer) => ctx.table.new_integer_var(),
+                    VariableKind::Ty(TyVariableKind::Float) => ctx.table.new_float_var(),
+                    // HACK: Chalk can sometimes return new lifetime variables. We
+                    // want to just skip them, but to not mess up the indices of
+                    // other variables, we'll just create a new type variable in
+                    // their place instead. This should not matter (we never see the
+                    // actual *uses* of the lifetime variable).
+                    VariableKind::Lifetime => ctx.table.new_type_var(),
+                    _ => panic!("const variable in solution"),
                 })
                 .collect(),
         );
@@ -147,8 +160,8 @@ impl<T> Canonicalized<T> {
 pub(crate) fn unify(tys: &Canonical<(Ty, Ty)>) -> Option<Substitution> {
     let mut table = InferenceTable::new();
     let vars = Substitution(
-        tys.kinds
-            .iter()
+        tys.binders
+            .iter(&Interner)
             // we always use type vars here because we want everything to
             // fallback to Unknown in the end (kind of hacky, as below)
             .map(|_| table.new_type_var())
@@ -170,7 +183,7 @@ pub(crate) fn unify(tys: &Canonical<(Ty, Ty)>) -> Option<Substitution> {
         }
     }
     Some(
-        Substitution::builder(tys.kinds.len())
+        Substitution::builder(tys.binders.len(&Interner))
             .fill(vars.iter().map(|v| table.resolve_ty_completely(v.clone())))
             .build(),
     )
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index 90b5b17e2..0f49dd39b 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -61,6 +61,8 @@ pub type ClosureId = chalk_ir::ClosureId<Interner>;
 pub type OpaqueTyId = chalk_ir::OpaqueTyId<Interner>;
 pub type PlaceholderIndex = chalk_ir::PlaceholderIndex;
 
+pub type CanonicalVarKinds = chalk_ir::CanonicalVarKinds<Interner>;
+
 pub type ChalkTraitId = chalk_ir::TraitId<Interner>;
 
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
@@ -662,12 +664,18 @@ impl QuantifiedWhereClauses {
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Canonical<T> {
     pub value: T,
-    pub kinds: Arc<[TyVariableKind]>,
+    pub binders: CanonicalVarKinds,
 }
 
 impl<T> Canonical<T> {
     pub fn new(value: T, kinds: impl IntoIterator<Item = TyVariableKind>) -> Self {
-        Self { value, kinds: kinds.into_iter().collect() }
+        let kinds = kinds.into_iter().map(|tk| {
+            chalk_ir::CanonicalVarKind::new(
+                chalk_ir::VariableKind::Ty(tk),
+                chalk_ir::UniverseIndex::ROOT,
+            )
+        });
+        Self { value, binders: chalk_ir::CanonicalVarKinds::from_iter(&Interner, kinds) }
     }
 }
 
diff --git a/crates/hir_ty/src/method_resolution.rs b/crates/hir_ty/src/method_resolution.rs
index da6bc2a4a..8e986ddde 100644
--- a/crates/hir_ty/src/method_resolution.rs
+++ b/crates/hir_ty/src/method_resolution.rs
@@ -6,7 +6,7 @@ use std::{iter, sync::Arc};
 
 use arrayvec::ArrayVec;
 use base_db::CrateId;
-use chalk_ir::{cast::Cast, Mutability};
+use chalk_ir::{cast::Cast, Mutability, UniverseIndex};
 use hir_def::{
     lang_item::LangItemTarget, AssocContainerId, AssocItemId, FunctionId, GenericDefId, HasModule,
     ImplId, Lookup, ModuleId, TraitId,
@@ -21,8 +21,9 @@ use crate::{
     primitive::{self, FloatTy, IntTy, UintTy},
     to_chalk_trait_id,
     utils::all_super_traits,
-    AdtId, Canonical, DebruijnIndex, FnPointer, FnSig, ForeignDefId, InEnvironment, Interner,
-    Scalar, Substitution, TraitEnvironment, TraitRef, Ty, TyKind, TypeWalk,
+    AdtId, Canonical, CanonicalVarKinds, DebruijnIndex, FnPointer, FnSig, ForeignDefId,
+    InEnvironment, Interner, Scalar, Substitution, TraitEnvironment, TraitRef, Ty, TyKind,
+    TypeWalk,
 };
 
 /// This is used as a key for indexing impls.
@@ -375,7 +376,7 @@ fn iterate_method_candidates_impl(
             // Also note that when we've got a receiver like &S, even if the method we
             // find in the end takes &self, we still do the autoderef step (just as
             // rustc does an autoderef and then autoref again).
-            let ty = InEnvironment { value: ty.clone(), environment: env.clone() };
+            let ty = InEnvironment { goal: ty.clone(), environment: env.env.clone() };
 
             // We have to be careful about the order we're looking at candidates
             // in here. Consider the case where we're resolving `x.clone()`
@@ -443,7 +444,7 @@ fn iterate_method_candidates_with_autoref(
         return true;
     }
     let refed = Canonical {
-        kinds: deref_chain[0].kinds.clone(),
+        binders: deref_chain[0].binders.clone(),
         value: TyKind::Ref(Mutability::Not, deref_chain[0].value.clone()).intern(&Interner),
     };
     if iterate_method_candidates_by_receiver(
@@ -459,7 +460,7 @@ fn iterate_method_candidates_with_autoref(
         return true;
     }
     let ref_muted = Canonical {
-        kinds: deref_chain[0].kinds.clone(),
+        binders: deref_chain[0].binders.clone(),
         value: TyKind::Ref(Mutability::Mut, deref_chain[0].value.clone()).intern(&Interner),
     };
     if iterate_method_candidates_by_receiver(
@@ -621,7 +622,7 @@ pub fn resolve_indexing_op(
     krate: CrateId,
     index_trait: TraitId,
 ) -> Option<Canonical<Ty>> {
-    let ty = InEnvironment { value: ty.clone(), environment: env.clone() };
+    let ty = InEnvironment { goal: ty.clone(), environment: env.env.clone() };
     let deref_chain = autoderef_method_receiver(db, krate, ty);
     for ty in deref_chain {
         let goal = generic_implements_goal(db, env.clone(), index_trait, ty.clone());
@@ -677,19 +678,28 @@ pub(crate) fn inherent_impl_substs(
     // we create a var for each type parameter of the impl; we need to keep in
     // mind here that `self_ty` might have vars of its own
     let vars = Substitution::build_for_def(db, impl_id)
-        .fill_with_bound_vars(DebruijnIndex::INNERMOST, self_ty.kinds.len())
+        .fill_with_bound_vars(DebruijnIndex::INNERMOST, self_ty.binders.len(&Interner))
         .build();
     let self_ty_with_vars = db.impl_self_ty(impl_id).subst(&vars);
-    let mut kinds = self_ty.kinds.to_vec();
-    kinds.extend(iter::repeat(chalk_ir::TyVariableKind::General).take(vars.len()));
-    let tys = Canonical { kinds: kinds.into(), value: (self_ty_with_vars, self_ty.value.clone()) };
+    let mut kinds = self_ty.binders.interned().to_vec();
+    kinds.extend(
+        iter::repeat(chalk_ir::WithKind::new(
+            chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
+            UniverseIndex::ROOT,
+        ))
+        .take(vars.len()),
+    );
+    let tys = Canonical {
+        binders: CanonicalVarKinds::from_iter(&Interner, kinds),
+        value: (self_ty_with_vars, self_ty.value.clone()),
+    };
     let substs = super::infer::unify(&tys);
     // We only want the substs for the vars we added, not the ones from self_ty.
     // Also, if any of the vars we added are still in there, we replace them by
     // Unknown. I think this can only really happen if self_ty contained
     // Unknown, and in that case we want the result to contain Unknown in those
     // places again.
-    substs.map(|s| fallback_bound_vars(s.suffix(vars.len()), self_ty.kinds.len()))
+    substs.map(|s| fallback_bound_vars(s.suffix(vars.len()), self_ty.binders.len(&Interner)))
 }
 
 /// This replaces any 'free' Bound vars in `s` (i.e. those with indices past
@@ -768,15 +778,24 @@ fn generic_implements_goal(
     trait_: TraitId,
     self_ty: Canonical<Ty>,
 ) -> Canonical<InEnvironment<super::DomainGoal>> {
-    let mut kinds = self_ty.kinds.to_vec();
+    let mut kinds = self_ty.binders.interned().to_vec();
     let substs = super::Substitution::build_for_def(db, trait_)
         .push(self_ty.value)
         .fill_with_bound_vars(DebruijnIndex::INNERMOST, kinds.len())
         .build();
-    kinds.extend(iter::repeat(chalk_ir::TyVariableKind::General).take(substs.len() - 1));
+    kinds.extend(
+        iter::repeat(chalk_ir::WithKind::new(
+            chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
+            UniverseIndex::ROOT,
+        ))
+        .take(substs.len() - 1),
+    );
     let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs };
     let obligation = trait_ref.cast(&Interner);
-    Canonical { kinds: kinds.into(), value: InEnvironment::new(env, obligation) }
+    Canonical {
+        binders: CanonicalVarKinds::from_iter(&Interner, kinds),
+        value: InEnvironment::new(env.env.clone(), obligation),
+    }
 }
 
 fn autoderef_method_receiver(
@@ -789,9 +808,9 @@ fn autoderef_method_receiver(
     if let Some(TyKind::Array(parameters)) =
         deref_chain.last().map(|ty| ty.value.interned(&Interner))
     {
-        let kinds = deref_chain.last().unwrap().kinds.clone();
+        let kinds = deref_chain.last().unwrap().binders.clone();
         let unsized_ty = TyKind::Slice(parameters.clone()).intern(&Interner);
-        deref_chain.push(Canonical { value: unsized_ty, kinds })
+        deref_chain.push(Canonical { value: unsized_ty, binders: kinds })
     }
     deref_chain
 }
diff --git a/crates/hir_ty/src/traits.rs b/crates/hir_ty/src/traits.rs
index 7dadd1ffb..ccee0e5ad 100644
--- a/crates/hir_ty/src/traits.rs
+++ b/crates/hir_ty/src/traits.rs
@@ -1,6 +1,5 @@
 //! Trait solving using Chalk.
 use std::env::var;
-use std::sync::Arc;
 
 use base_db::CrateId;
 use chalk_ir::cast::Cast;
@@ -44,7 +43,7 @@ pub struct TraitEnvironment {
     // When we're using Chalk's Ty we can make this a BTreeMap since it's Ord,
     // but for now it's too annoying...
     pub(crate) traits_from_clauses: Vec<(Ty, TraitId)>,
-    pub(crate) env: chalk_ir::Environment<Interner>,
+    pub env: chalk_ir::Environment<Interner>,
 }
 
 impl TraitEnvironment {
@@ -74,13 +73,13 @@ impl Default for TraitEnvironment {
 /// Something (usually a goal), along with an environment.
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub struct InEnvironment<T> {
-    pub environment: Arc<TraitEnvironment>,
-    pub value: T,
+    pub environment: chalk_ir::Environment<Interner>,
+    pub goal: T,
 }
 
 impl<T> InEnvironment<T> {
-    pub fn new(environment: Arc<TraitEnvironment>, value: T) -> InEnvironment<T> {
-        InEnvironment { environment, value }
+    pub fn new(environment: chalk_ir::Environment<Interner>, value: T) -> InEnvironment<T> {
+        InEnvironment { environment, goal: value }
     }
 }
 
@@ -126,18 +125,18 @@ pub(crate) fn trait_solve_query(
     krate: CrateId,
     goal: Canonical<InEnvironment<DomainGoal>>,
 ) -> Option<Solution> {
-    let _p = profile::span("trait_solve_query").detail(|| match &goal.value.value {
+    let _p = profile::span("trait_solve_query").detail(|| match &goal.value.goal {
         DomainGoal::Holds(WhereClause::Implemented(it)) => {
             db.trait_data(it.hir_trait_id()).name.to_string()
         }
         DomainGoal::Holds(WhereClause::AliasEq(_)) => "alias_eq".to_string(),
     });
-    log::info!("trait_solve_query({})", goal.value.value.display(db));
+    log::info!("trait_solve_query({})", goal.value.goal.display(db));
 
     if let DomainGoal::Holds(WhereClause::AliasEq(AliasEq {
         alias: AliasTy::Projection(projection_ty),
         ..
-    })) = &goal.value.value
+    })) = &goal.value.goal
     {
         if let TyKind::BoundVar(_) = &projection_ty.substitution[0].interned(&Interner) {
             // Hack: don't ask Chalk to normalize with an unknown self type, it'll say that's impossible
diff --git a/crates/hir_ty/src/traits/chalk/mapping.rs b/crates/hir_ty/src/traits/chalk/mapping.rs
index 7209dd14e..aef6b8a15 100644
--- a/crates/hir_ty/src/traits/chalk/mapping.rs
+++ b/crates/hir_ty/src/traits/chalk/mapping.rs
@@ -439,35 +439,12 @@ where
     type Chalk = chalk_ir::Canonical<T::Chalk>;
 
     fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::Canonical<T::Chalk> {
-        let kinds = self.kinds.iter().map(|&tk| {
-            chalk_ir::CanonicalVarKind::new(
-                chalk_ir::VariableKind::Ty(tk),
-                chalk_ir::UniverseIndex::ROOT,
-            )
-        });
         let value = self.value.to_chalk(db);
-        chalk_ir::Canonical {
-            value,
-            binders: chalk_ir::CanonicalVarKinds::from_iter(&Interner, kinds),
-        }
+        chalk_ir::Canonical { value, binders: self.binders }
     }
 
     fn from_chalk(db: &dyn HirDatabase, canonical: chalk_ir::Canonical<T::Chalk>) -> Canonical<T> {
-        let kinds = canonical
-            .binders
-            .iter(&Interner)
-            .map(|k| match k.kind {
-                chalk_ir::VariableKind::Ty(tk) => tk,
-                // HACK: Chalk can sometimes return new lifetime variables. We
-                // want to just skip them, but to not mess up the indices of
-                // other variables, we'll just create a new type variable in
-                // their place instead. This should not matter (we never see the
-                // actual *uses* of the lifetime variable).
-                chalk_ir::VariableKind::Lifetime => chalk_ir::TyVariableKind::General,
-                chalk_ir::VariableKind::Const(_) => panic!("unexpected const from Chalk"),
-            })
-            .collect();
-        Canonical { kinds, value: from_chalk(db, canonical.value) }
+        Canonical { binders: canonical.binders, value: from_chalk(db, canonical.value) }
     }
 }
 
@@ -478,10 +455,7 @@ where
     type Chalk = chalk_ir::InEnvironment<T::Chalk>;
 
     fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::InEnvironment<T::Chalk> {
-        chalk_ir::InEnvironment {
-            environment: self.environment.env.clone(),
-            goal: self.value.to_chalk(db),
-        }
+        chalk_ir::InEnvironment { environment: self.environment, goal: self.goal.to_chalk(db) }
     }
 
     fn from_chalk(