11 files changed, 190 insertions, 160 deletions

diff --git a/crates/hir_ty/src/autoderef.rs b/crates/hir_ty/src/autoderef.rs
index c5890e24d..80e192a57 100644
--- a/crates/hir_ty/src/autoderef.rs
+++ b/crates/hir_ty/src/autoderef.rs
@@ -120,8 +120,8 @@ 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.binders.len(&Interner) {
-                if vars.0.value.at(&Interner, i - 1).assert_ty_ref(&Interner).kind(&Interner)
+            for i in 1..vars.binders.len(&Interner) {
+                if vars.value.subst.at(&Interner, i - 1).assert_ty_ref(&Interner).kind(&Interner)
                     != &TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, i - 1))
                 {
                     warn!("complex solution for derefing {:?}: {:?}, ignoring", ty.goal, solution);
@@ -130,12 +130,12 @@ fn deref_by_trait(
             }
             Some(Canonical {
                 value: vars
-                    .0
                     .value
-                    .at(&Interner, vars.0.value.len(&Interner) - 1)
+                    .subst
+                    .at(&Interner, vars.value.subst.len(&Interner) - 1)
                     .assert_ty_ref(&Interner)
                     .clone(),
-                binders: vars.0.binders.clone(),
+                binders: vars.binders.clone(),
             })
         }
         Solution::Ambig(_) => {
diff --git a/crates/hir_ty/src/infer.rs b/crates/hir_ty/src/infer.rs
index 796f77ab0..6af0c59b8 100644
--- a/crates/hir_ty/src/infer.rs
+++ b/crates/hir_ty/src/infer.rs
@@ -42,7 +42,7 @@ use super::{
 };
 use crate::{
     db::HirDatabase, infer::diagnostics::InferenceDiagnostic, lower::ImplTraitLoweringMode,
-    to_assoc_type_id, AliasEq, AliasTy, Interner, TyBuilder, TyExt, TyKind,
+    to_assoc_type_id, AliasEq, AliasTy, Canonical, Interner, TyBuilder, TyExt, TyKind,
 };
 
 // This lint has a false positive here. See the link below for details.
@@ -131,8 +131,7 @@ pub struct InferenceResult {
     method_resolutions: FxHashMap<ExprId, FunctionId>,
     /// For each field access expr, records the field it resolves to.
     field_resolutions: FxHashMap<ExprId, FieldId>,
-    record_pat_field_resolutions: FxHashMap<PatId, FieldId>,
-    /// For each struct literal, records the variant it resolves to.
+    /// For each struct literal or pattern, records the variant it resolves to.
     variant_resolutions: FxHashMap<ExprOrPatId, VariantId>,
     /// For each associated item record what it resolves to
     assoc_resolutions: FxHashMap<ExprOrPatId, AssocItemId>,
@@ -151,9 +150,6 @@ impl InferenceResult {
     pub fn field_resolution(&self, expr: ExprId) -> Option<FieldId> {
         self.field_resolutions.get(&expr).copied()
     }
-    pub fn record_pat_field_resolution(&self, pat: PatId) -> Option<FieldId> {
-        self.record_pat_field_resolutions.get(&pat).copied()
-    }
     pub fn variant_resolution_for_expr(&self, id: ExprId) -> Option<VariantId> {
         self.variant_resolutions.get(&id.into()).copied()
     }
@@ -346,11 +342,18 @@ impl<'a> InferenceContext<'a> {
                 self.db.trait_solve(self.resolver.krate().unwrap(), canonicalized.value.clone());
 
             match solution {
-                Some(Solution::Unique(substs)) => {
-                    canonicalized.apply_solution(self, substs.0);
+                Some(Solution::Unique(canonical_subst)) => {
+                    canonicalized.apply_solution(
+                        self,
+                        Canonical {
+                            binders: canonical_subst.binders,
+                            // FIXME: handle constraints
+                            value: canonical_subst.value.subst,
+                        },
+                    );
                 }
                 Some(Solution::Ambig(Guidance::Definite(substs))) => {
-                    canonicalized.apply_solution(self, substs.0);
+                    canonicalized.apply_solution(self, substs);
                     self.obligations.push(obligation);
                 }
                 Some(_) => {
@@ -691,25 +694,6 @@ impl<'a> InferenceContext<'a> {
     }
 }
 
-/// The kinds of placeholders we need during type inference. There's separate
-/// values for general types, and for integer and float variables. The latter
-/// two are used for inference of literal values (e.g. `100` could be one of
-/// several integer types).
-#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
-pub struct InferenceVar {
-    index: u32,
-}
-
-impl InferenceVar {
-    fn to_inner(self) -> unify::TypeVarId {
-        unify::TypeVarId(self.index)
-    }
-
-    fn from_inner(unify::TypeVarId(index): unify::TypeVarId) -> Self {
-        InferenceVar { index }
-    }
-}
-
 /// When inferring an expression, we propagate downward whatever type hint we
 /// are able in the form of an `Expectation`.
 #[derive(Clone, PartialEq, Eq, Debug)]
diff --git a/crates/hir_ty/src/infer/coerce.rs b/crates/hir_ty/src/infer/coerce.rs
index 159a53a63..f1af2a0bd 100644
--- a/crates/hir_ty/src/infer/coerce.rs
+++ b/crates/hir_ty/src/infer/coerce.rs
@@ -7,7 +7,7 @@
 use chalk_ir::{cast::Cast, Mutability, TyVariableKind};
 use hir_def::lang_item::LangItemTarget;
 
-use crate::{autoderef, Interner, Solution, Ty, TyBuilder, TyExt, TyKind};
+use crate::{autoderef, Canonical, Interner, Solution, Ty, TyBuilder, TyExt, TyKind};
 
 use super::{InEnvironment, InferenceContext};
 
@@ -148,7 +148,14 @@ impl<'a> InferenceContext<'a> {
 
         match solution {
             Solution::Unique(v) => {
-                canonicalized.apply_solution(self, v.0);
+                canonicalized.apply_solution(
+                    self,
+                    Canonical {
+                        binders: v.binders,
+                        // FIXME handle constraints
+                        value: v.value.subst,
+                    },
+                );
             }
             _ => return None,
         };
diff --git a/crates/hir_ty/src/infer/pat.rs b/crates/hir_ty/src/infer/pat.rs
index 942f70edf..e4813c87c 100644
--- a/crates/hir_ty/src/infer/pat.rs
+++ b/crates/hir_ty/src/infer/pat.rs
@@ -7,7 +7,6 @@ use chalk_ir::Mutability;
 use hir_def::{
     expr::{BindingAnnotation, Expr, Literal, Pat, PatId, RecordFieldPat},
     path::Path,
-    FieldId,
 };
 use hir_expand::name::Name;
 
@@ -80,11 +79,6 @@ impl<'a> InferenceContext<'a> {
         let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
         for subpat in subpats {
             let matching_field = var_data.as_ref().and_then(|it| it.field(&subpat.name));
-            if let Some(local_id) = matching_field {
-                let field_def = FieldId { parent: def.unwrap(), local_id };
-                self.result.record_pat_field_resolutions.insert(subpat.pat, field_def);
-            }
-
             let expected_ty = matching_field.map_or(self.err_ty(), |field| {
                 field_tys[field].clone().substitute(&Interner, &substs)
             });
diff --git a/crates/hir_ty/src/infer/unify.rs b/crates/hir_ty/src/infer/unify.rs
index 7d76cda68..d717e3375 100644
--- a/crates/hir_ty/src/infer/unify.rs
+++ b/crates/hir_ty/src/infer/unify.rs
@@ -51,7 +51,7 @@ impl<'a, 'b> Canonicalizer<'a, 'b> {
         t.fold_binders(
             &mut |ty, binders| match ty.kind(&Interner) {
                 &TyKind::InferenceVar(var, kind) => {
-                    let inner = var.to_inner();
+                    let inner = from_inference_var(var);
                     if self.var_stack.contains(&inner) {
                         // recursive type
                         return self.ctx.table.type_variable_table.fallback_value(var, kind);
@@ -65,7 +65,7 @@ impl<'a, 'b> Canonicalizer<'a, 'b> {
                         result
                     } else {
                         let root = self.ctx.table.var_unification_table.find(inner);
-                        let position = self.add(InferenceVar::from_inner(root), kind);
+                        let position = self.add(to_inference_var(root), kind);
                         TyKind::BoundVar(BoundVar::new(binders, position)).intern(&Interner)
                     }
                 }
@@ -207,16 +207,16 @@ impl TypeVariableTable {
     }
 
     pub(super) fn set_diverging(&mut self, iv: InferenceVar, diverging: bool) {
-        self.inner[iv.to_inner().0 as usize].diverging = diverging;
+        self.inner[from_inference_var(iv).0 as usize].diverging = diverging;
     }
 
     fn is_diverging(&mut self, iv: InferenceVar) -> bool {
-        self.inner[iv.to_inner().0 as usize].diverging
+        self.inner[from_inference_var(iv).0 as usize].diverging
     }
 
     fn fallback_value(&self, iv: InferenceVar, kind: TyVariableKind) -> Ty {
         match kind {
-            _ if self.inner[iv.to_inner().0 as usize].diverging => TyKind::Never,
+            _ if self.inner[from_inference_var(iv).0 as usize].diverging => TyKind::Never,
             TyVariableKind::General => TyKind::Error,
             TyVariableKind::Integer => TyKind::Scalar(Scalar::Int(IntTy::I32)),
             TyVariableKind::Float => TyKind::Scalar(Scalar::Float(FloatTy::F64)),
@@ -250,7 +250,7 @@ impl InferenceTable {
         self.type_variable_table.push(TypeVariableData { diverging });
         let key = self.var_unification_table.new_key(TypeVarValue::Unknown);
         assert_eq!(key.0 as usize, self.type_variable_table.inner.len() - 1);
-        TyKind::InferenceVar(InferenceVar::from_inner(key), kind).intern(&Interner)
+        TyKind::InferenceVar(to_inference_var(key), kind).intern(&Interner)
     }
 
     pub(crate) fn new_type_var(&mut self) -> Ty {
@@ -369,8 +369,12 @@ impl InferenceTable {
                 == self.type_variable_table.is_diverging(*tv2) =>
             {
                 // both type vars are unknown since we tried to resolve them
-                if !self.var_unification_table.unioned(tv1.to_inner(), tv2.to_inner()) {
-                    self.var_unification_table.union(tv1.to_inner(), tv2.to_inner());
+                if !self
+                    .var_unification_table
+                    .unioned(from_inference_var(*tv1), from_inference_var(*tv2))
+                {
+                    self.var_unification_table
+                        .union(from_inference_var(*tv1), from_inference_var(*tv2));
                     self.revision += 1;
                 }
                 true
@@ -407,7 +411,7 @@ impl InferenceTable {
             ) => {
                 // the type var is unknown since we tried to resolve it
                 self.var_unification_table.union_value(
-                    tv.to_inner(),
+                    from_inference_var(*tv),
                     TypeVarValue::Known(other.clone().intern(&Interner)),
                 );
                 self.revision += 1;
@@ -462,7 +466,7 @@ impl InferenceTable {
             }
             match ty.kind(&Interner) {
                 TyKind::InferenceVar(tv, _) => {
-                    let inner = tv.to_inner();
+                    let inner = from_inference_var(*tv);
                     match self.var_unification_table.inlined_probe_value(inner).known() {
                         Some(known_ty) => {
                             // The known_ty can't be a type var itself
@@ -485,7 +489,7 @@ impl InferenceTable {
     fn resolve_ty_as_possible_inner(&mut self, tv_stack: &mut Vec<TypeVarId>, ty: Ty) -> Ty {
         ty.fold(&mut |ty| match ty.kind(&Interner) {
             &TyKind::InferenceVar(tv, kind) => {
-                let inner = tv.to_inner();
+                let inner = from_inference_var(tv);
                 if tv_stack.contains(&inner) {
                     cov_mark::hit!(type_var_cycles_resolve_as_possible);
                     // recursive type
@@ -512,7 +516,7 @@ impl InferenceTable {
     fn resolve_ty_completely_inner(&mut self, tv_stack: &mut Vec<TypeVarId>, ty: Ty) -> Ty {
         ty.fold(&mut |ty| match ty.kind(&Interner) {
             &TyKind::InferenceVar(tv, kind) => {
-                let inner = tv.to_inner();
+                let inner = from_inference_var(tv);
                 if tv_stack.contains(&inner) {
                     cov_mark::hit!(type_var_cycles_resolve_completely);
                     // recursive type
@@ -555,6 +559,14 @@ impl UnifyKey for TypeVarId {
     }
 }
 
+fn from_inference_var(var: InferenceVar) -> TypeVarId {
+    TypeVarId(var.index())
+}
+
+fn to_inference_var(TypeVarId(index): TypeVarId) -> InferenceVar {
+    index.into()
+}
+
 /// The value of a type variable: either we already know the type, or we don't
 /// know it yet.
 #[derive(Clone, PartialEq, Eq, Debug)]
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index f5b658cba..5c83a508d 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -42,7 +42,7 @@ use crate::{db::HirDatabase, display::HirDisplay, utils::generics};
 pub use autoderef::autoderef;
 pub use builder::TyBuilder;
 pub use chalk_ext::{ProjectionTyExt, TyExt};
-pub use infer::{could_unify, InferenceResult, InferenceVar};
+pub use infer::{could_unify, InferenceResult};
 pub use lower::{
     associated_type_shorthand_candidates, callable_item_sig, CallableDefId, ImplTraitLoweringMode,
     TyDefId, TyLoweringContext, ValueTyDefId,
diff --git a/crates/hir_ty/src/method_resolution.rs b/crates/hir_ty/src/method_resolution.rs
index ee725fd46..f29319f20 100644
--- a/crates/hir_ty/src/method_resolution.rs
+++ b/crates/hir_ty/src/method_resolution.rs
@@ -8,8 +8,8 @@ use arrayvec::ArrayVec;
 use base_db::CrateId;
 use chalk_ir::{cast::Cast, Mutability, UniverseIndex};
 use hir_def::{
-    lang_item::LangItemTarget, AssocContainerId, AssocItemId, FunctionId, GenericDefId, HasModule,
-    ImplId, Lookup, ModuleId, TraitId,
+    lang_item::LangItemTarget, nameres::DefMap, AssocContainerId, AssocItemId, FunctionId,
+    GenericDefId, HasModule, ImplId, Lookup, ModuleId, TraitId,
 };
 use hir_expand::name::Name;
 use rustc_hash::{FxHashMap, FxHashSet};
@@ -100,25 +100,38 @@ impl TraitImpls {
         let mut impls = Self { map: FxHashMap::default() };
 
         let crate_def_map = db.crate_def_map(krate);
-        for (_module_id, module_data) in crate_def_map.modules() {
-            for impl_id in module_data.scope.impls() {
-                let target_trait = match db.impl_trait(impl_id) {
-                    Some(tr) => tr.skip_binders().hir_trait_id(),
-                    None => continue,
-                };
-                let self_ty = db.impl_self_ty(impl_id);
-                let self_ty_fp = TyFingerprint::for_impl(self_ty.skip_binders());
-                impls
-                    .map
-                    .entry(target_trait)
-                    .or_default()
-                    .entry(self_ty_fp)
-                    .or_default()
-                    .push(impl_id);
+        collect_def_map(db, &crate_def_map, &mut impls);
+
+        return Arc::new(impls);
+
+        fn collect_def_map(db: &dyn HirDatabase, def_map: &DefMap, impls: &mut TraitImpls) {
+            for (_module_id, module_data) in def_map.modules() {
+                for impl_id in module_data.scope.impls() {
+                    let target_trait = match db.impl_trait(impl_id) {
+                        Some(tr) => tr.skip_binders().hir_trait_id(),
+                        None => continue,
+                    };
+                    let self_ty = db.impl_self_ty(impl_id);
+                    let self_ty_fp = TyFingerprint::for_impl(self_ty.skip_binders());
+                    impls
+                        .map
+                        .entry(target_trait)
+                        .or_default()
+                        .entry(self_ty_fp)
+                        .or_default()
+                        .push(impl_id);
+                }
+
+                // To better support custom derives, collect impls in all unnamed const items.
+                // const _: () = { ... };
+                for konst in module_data.scope.unnamed_consts() {
+                    let body = db.body(konst.into());
+                    for (_, block_def_map) in body.blocks(db.upcast()) {
+                        collect_def_map(db, &block_def_map, impls);
+                    }
+                }
             }
         }
-
-        Arc::new(impls)
     }
 
     pub(crate) fn trait_impls_in_deps_query(db: &dyn HirDatabase, krate: CrateId) -> Arc<Self> {
@@ -208,6 +221,9 @@ impl InherentImpls {
             }
         }
 
+        // NOTE: We're not collecting inherent impls from unnamed consts here, we intentionally only
+        // support trait impls there.
+
         Arc::new(Self { map })
     }
 
diff --git a/crates/hir_ty/src/tests/method_resolution.rs b/crates/hir_ty/src/tests/method_resolution.rs
index 61f18b0d2..4b2c82b41 100644
--- a/crates/hir_ty/src/tests/method_resolution.rs
+++ b/crates/hir_ty/src/tests/method_resolution.rs
@@ -1292,3 +1292,25 @@ mod b {
         "#]],
     )
 }
+
+#[test]
+fn impl_in_unnamed_const() {
+    check_types(
+        r#"
+struct S;
+
+trait Tr {
+    fn method(&self) -> u16;
+}
+
+const _: () = {
+    impl Tr for S {}
+};
+
+fn f() {
+    S.method();
+  //^^^^^^^^^^ u16
+}
+    "#,
+    );
+}
diff --git a/crates/hir_ty/src/traits.rs b/crates/hir_ty/src/traits.rs
index c8883485c..3374532c3 100644
--- a/crates/hir_ty/src/traits.rs
+++ b/crates/hir_ty/src/traits.rs
@@ -9,7 +9,7 @@ use stdx::panic_context;
 
 use crate::{
     db::HirDatabase, AliasEq, AliasTy, Canonical, DomainGoal, Guidance, HirDisplay, InEnvironment,
-    Solution, SolutionVariables, Ty, TyKind, WhereClause,
+    Solution, Ty, TyKind, WhereClause,
 };
 
 use self::chalk::{from_chalk, Interner, ToChalk};
@@ -173,23 +173,15 @@ fn solution_from_chalk(
     db: &dyn HirDatabase,
     solution: chalk_solve::Solution<Interner>,
 ) -> Solution {
-    let convert_subst = |subst: chalk_ir::Canonical<chalk_ir::Substitution<Interner>>| {
-        let result = from_chalk(db, subst);
-        SolutionVariables(result)
-    };
     match solution {
         chalk_solve::Solution::Unique(constr_subst) => {
-            let subst = chalk_ir::Canonical {
-                value: constr_subst.value.subst,
-                binders: constr_subst.binders,
-            };
-            Solution::Unique(convert_subst(subst))
+            Solution::Unique(from_chalk(db, constr_subst))
         }
         chalk_solve::Solution::Ambig(chalk_solve::Guidance::Definite(subst)) => {
-            Solution::Ambig(Guidance::Definite(convert_subst(subst)))
+            Solution::Ambig(Guidance::Definite(from_chalk(db, subst)))
         }
         chalk_solve::Solution::Ambig(chalk_solve::Guidance::Suggested(subst)) => {
-            Solution::Ambig(Guidance::Suggested(convert_subst(subst)))
+            Solution::Ambig(Guidance::Suggested(from_chalk(db, subst)))
         }
         chalk_solve::Solution::Ambig(chalk_solve::Guidance::Unknown) => {
             Solution::Ambig(Guidance::Unknown)
diff --git a/crates/hir_ty/src/traits/chalk/mapping.rs b/crates/hir_ty/src/traits/chalk/mapping.rs
index cf73cb078..84abd99b2 100644
--- a/crates/hir_ty/src/traits/chalk/mapping.rs
+++ b/crates/hir_ty/src/traits/chalk/mapping.rs
@@ -10,10 +10,9 @@ use base_db::salsa::InternKey;
 use hir_def::{GenericDefId, TypeAliasId};
 
 use crate::{
-    chalk_ext::ProjectionTyExt, db::HirDatabase, dummy_usize_const, static_lifetime, AliasTy,
-    CallableDefId, Canonical, Const, DomainGoal, FnPointer, GenericArg, InEnvironment, Lifetime,
-    OpaqueTy, ProjectionTy, QuantifiedWhereClause, Substitution, TraitRef, Ty, TypeWalk,
-    WhereClause,
+    chalk_ext::ProjectionTyExt, db::HirDatabase, static_lifetime, AliasTy, CallableDefId,
+    Canonical, ConstrainedSubst, DomainGoal, FnPointer, GenericArg, InEnvironment, OpaqueTy,
+    ProjectionTy, QuantifiedWhereClause, Substitution, TraitRef, Ty, TypeWalk, WhereClause,
 };
 
 use super::interner::*;
@@ -23,16 +22,16 @@ impl ToChalk for Ty {
     type Chalk = chalk_ir::Ty<Interner>;
     fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::Ty<Interner> {
         match self.into_inner() {
-            TyKind::Ref(m, lt, ty) => ref_to_chalk(db, m, lt, ty),
-            TyKind::Array(ty, size) => array_to_chalk(db, ty, size),
-            TyKind::Function(FnPointer { sig, substitution: substs, .. }) => {
+            TyKind::Ref(m, lt, ty) => {
+                chalk_ir::TyKind::Ref(m, lt, ty.to_chalk(db)).intern(&Interner)
+            }
+            TyKind::Array(ty, size) => {
+                chalk_ir::TyKind::Array(ty.to_chalk(db), size).intern(&Interner)
+            }
+            TyKind::Function(FnPointer { sig, substitution: substs, num_binders }) => {
                 let substitution = chalk_ir::FnSubst(substs.0.to_chalk(db));
-                chalk_ir::TyKind::Function(chalk_ir::FnPointer {
-                    num_binders: 0,
-                    sig,
-                    substitution,
-                })
-                .intern(&Interner)
+                chalk_ir::TyKind::Function(chalk_ir::FnPointer { num_binders, sig, substitution })
+                    .intern(&Interner)
             }
             TyKind::AssociatedType(assoc_type_id, substs) => {
                 let substitution = substs.to_chalk(db);
@@ -74,22 +73,13 @@ impl ToChalk for Ty {
                 chalk_ir::TyKind::Adt(adt_id, substitution).intern(&Interner)
             }
             TyKind::Alias(AliasTy::Projection(proj_ty)) => {
-                let associated_ty_id = proj_ty.associated_ty_id;
-                let substitution = proj_ty.substitution.to_chalk(db);
-                chalk_ir::AliasTy::Projection(chalk_ir::ProjectionTy {
-                    associated_ty_id,
-                    substitution,
-                })
-                .cast(&Interner)
-                .intern(&Interner)
-            }
-            TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
-                let opaque_ty_id = opaque_ty.opaque_ty_id;
-                let substitution = opaque_ty.substitution.to_chalk(db);
-                chalk_ir::AliasTy::Opaque(chalk_ir::OpaqueTy { opaque_ty_id, substitution })
+                chalk_ir::AliasTy::Projection(proj_ty.to_chalk(db))
                     .cast(&Interner)
                     .intern(&Interner)
             }
+            TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
+                chalk_ir::AliasTy::Opaque(opaque_ty.to_chalk(db)).cast(&Interner).intern(&Interner)
+            }
             TyKind::Placeholder(idx) => idx.to_ty::<Interner>(&Interner),
             TyKind::BoundVar(idx) => chalk_ir::TyKind::BoundVar(idx).intern(&Interner),
             TyKind::InferenceVar(..) => panic!("uncanonicalized infer ty"),
@@ -101,7 +91,7 @@ impl ToChalk for Ty {
                 );
                 let bounded_ty = chalk_ir::DynTy {
                     bounds: chalk_ir::Binders::new(binders, where_clauses),
-                    lifetime: static_lifetime(),
+                    lifetime: dyn_ty.lifetime,
                 };
                 chalk_ir::TyKind::Dyn(bounded_ty).intern(&Interner)
             }
@@ -114,17 +104,10 @@ impl ToChalk for Ty {
             chalk_ir::TyKind::Array(ty, size) => TyKind::Array(from_chalk(db, ty), size),
             chalk_ir::TyKind::Placeholder(idx) => TyKind::Placeholder(idx),
             chalk_ir::TyKind::Alias(chalk_ir::AliasTy::Projection(proj)) => {
-                let associated_ty = proj.associated_ty_id;
-                let parameters = from_chalk(db, proj.substitution);
-                TyKind::Alias(AliasTy::Projection(ProjectionTy {
-                    associated_ty_id: associated_ty,
-                    substitution: parameters,
-                }))
+                TyKind::Alias(AliasTy::Projection(from_chalk(db, proj)))
             }
             chalk_ir::TyKind::Alias(chalk_ir::AliasTy::Opaque(opaque_ty)) => {
-                let opaque_ty_id = opaque_ty.opaque_ty_id;
-                let parameters = from_chalk(db, opaque_ty.substitution);
-                TyKind::Alias(AliasTy::Opaque(OpaqueTy { opaque_ty_id, substitution: parameters }))
+                TyKind::Alias(AliasTy::Opaque(from_chalk(db, opaque_ty)))
             }
             chalk_ir::TyKind::Function(chalk_ir::FnPointer {
                 num_binders,
@@ -138,18 +121,19 @@ impl ToChalk for Ty {
             }
             chalk_ir::TyKind::BoundVar(idx) => TyKind::BoundVar(idx),
             chalk_ir::TyKind::InferenceVar(_iv, _kind) => TyKind::Error,
-            chalk_ir::TyKind::Dyn(where_clauses) => {
-                assert_eq!(where_clauses.bounds.binders.len(&Interner), 1);
-                let bounds = where_clauses
-                    .bounds
-                    .skip_binders()
-                    .iter(&Interner)
-                    .map(|c| from_chalk(db, c.clone()));
+            chalk_ir::TyKind::Dyn(dyn_ty) => {
+                assert_eq!(dyn_ty.bounds.binders.len(&Interner), 1);
+                let (bounds, binders) = dyn_ty.bounds.into_value_and_skipped_binders();
+                let where_clauses = crate::QuantifiedWhereClauses::from_iter(
+                    &Interner,
+                    bounds.interned().iter().cloned().map(|p| from_chalk(db, p)),
+                );
                 TyKind::Dyn(crate::DynTy {
-                    bounds: crate::Binders::new(
-                        where_clauses.bounds.binders.clone(),
-                        crate::QuantifiedWhereClauses::from_iter(&Interner, bounds),
-                    ),
+                    bounds: crate::Binders::new(binders, where_clauses),
+                    // HACK: we sometimes get lifetime variables back in solutions
+                    // from Chalk, and don't have the infrastructure to substitute
+                    // them yet. So for now we just turn them into 'static right
+                    // when we get them
                     lifetime: static_lifetime(),
                 })
             }
@@ -169,8 +153,12 @@ impl ToChalk for Ty {
             }
             chalk_ir::TyKind::Raw(mutability, ty) => TyKind::Raw(mutability, from_chalk(db, ty)),
             chalk_ir::TyKind::Slice(ty) => TyKind::Slice(from_chalk(db, ty)),
-            chalk_ir::TyKind::Ref(mutability, lifetime, ty) => {
-                TyKind::Ref(mutability, lifetime, from_chalk(db, ty))
+            chalk_ir::TyKind::Ref(mutability, _lifetime, ty) => {
+                // HACK: we sometimes get lifetime variables back in solutions
+                // from Chalk, and don't have the infrastructure to substitute
+                // them yet. So for now we just turn them into 'static right
+                // when we get them
+                TyKind::Ref(mutability, static_lifetime(), from_chalk(db, ty))
             }
             chalk_ir::TyKind::Str => TyKind::Str,
             chalk_ir::TyKind::Never => TyKind::Never,
@@ -189,26 +177,6 @@ impl ToChalk for Ty {
     }
 }
 
-/// We currently don't model lifetimes, but Chalk does. So, we have to insert a
-/// fake lifetime here, because Chalks built-in logic may expect it to be there.
-fn ref_to_chalk(
-    db: &dyn HirDatabase,
-    mutability: chalk_ir::Mutability,
-    _lifetime: Lifetime,
-    ty: Ty,
-) -> chalk_ir::Ty<Interner> {
-    let arg = ty.to_chalk(db);
-    let lifetime = static_lifetime();
-    chalk_ir::TyKind::Ref(mutability, lifetime, arg).intern(&Interner)
-}
-
-/// We currently don't model constants, but Chalk does. So, we have to insert a
-/// fake constant here, because Chalks built-in logic may expect it to be there.
-fn array_to_chalk(db: &dyn HirDatabase, ty: Ty, _: Const) -> chalk_ir::Ty<Interner> {
-    let arg = ty.to_chalk(db);
-    chalk_ir::TyKind::Array(arg, dummy_usize_const()).intern(&Interner)
-}
-
 impl ToChalk for GenericArg {
     type Chalk = chalk_ir::GenericArg<Interner>;
 
@@ -491,6 +459,18 @@ where
     }
 }
 
+impl ToChalk for crate::ConstrainedSubst {
+    type Chalk = chalk_ir::ConstrainedSubst<Interner>;
+
+    fn to_chalk(self, _db: &dyn HirDatabase) -> Self::Chalk {
+        unimplemented!()
+    }
+
+    fn from_chalk(db: &dyn HirDatabase, chalk: Self::Chalk) -> Self {
+        ConstrainedSubst { subst: from_chalk(db, chalk.subst) }
+    }
+}
+
 pub(super) fn make_binders<T>(value: T, num_vars: usize) -> chalk_ir::Binders<T>
 where
     T: HasInterner<Interner = Interner>,
diff --git a/crates/hir_ty/src/types.rs b/crates/hir_ty/src/types.rs
index 89c0ddd1a..c25bc2d6a 100644
--- a/crates/hir_ty/src/types.rs
+++ b/crates/hir_ty/src/types.rs
@@ -11,8 +11,7 @@ use smallvec::SmallVec;
 
 use crate::{
     AssocTypeId, CanonicalVarKinds, ChalkTraitId, ClosureId, Const, FnDefId, FnSig, ForeignDefId,
-    InferenceVar, Interner, Lifetime, OpaqueTyId, PlaceholderIndex, TypeWalk, VariableKind,
-    VariableKinds,
+    Interner, Lifetime, OpaqueTyId, PlaceholderIndex, TypeWalk, VariableKind, VariableKinds,
 };
 
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
@@ -491,14 +490,16 @@ pub struct AliasEq {
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
-pub struct SolutionVariables(pub Canonical<Substitution>);
+pub struct ConstrainedSubst {
+    pub subst: Substitution,
+}
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 /// A (possible) solution for a proposed goal.
 pub enum Solution {
     /// The goal indeed holds, and there is a unique value for all existential
     /// variables.
-    Unique(SolutionVariables),
+    Unique(Canonical<ConstrainedSubst>),
 
     /// The goal may be provable in multiple ways, but regardless we may have some guidance
     /// for type inference. In this case, we don't return any lifetime
@@ -514,13 +515,35 @@ pub enum Guidance {
     /// The existential variables *must* have the given values if the goal is
     /// ever to hold, but that alone isn't enough to guarantee the goal will
     /// actually hold.
-    Definite(SolutionVariables),
+    Definite(Canonical<Substitution>),
 
     /// There are multiple plausible values for the existentials, but the ones
     /// here are suggested as the preferred choice heuristically. These should
     /// be used for inference fallback only.
-    Suggested(SolutionVariables),
+    Suggested(Canonical<Substitution>),
 
     /// There's no useful information to feed back to type inference
     Unknown,
 }
+
+/// The kinds of placeholders we need during type inference. There's separate
+/// values for general types, and for integer and float variables. The latter
+/// two are used for inference of literal values (e.g. `100` could be one of
+/// several integer types).
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+pub struct InferenceVar {
+    index: u32,
+}
+
+impl From<u32> for InferenceVar {
+    fn from(index: u32) -> InferenceVar {
+        InferenceVar { index }
+    }
+}
+
+impl InferenceVar {
+    /// Gets the underlying index value.
+    pub fn index(self) -> u32 {
+        self.index
+    }
+}