14 files changed, 73 insertions, 66 deletions

diff --git a/crates/hir_ty/src/chalk_ext.rs b/crates/hir_ty/src/chalk_ext.rs
index 6a353423a..28ed3aac6 100644
--- a/crates/hir_ty/src/chalk_ext.rs
+++ b/crates/hir_ty/src/chalk_ext.rs
@@ -202,12 +202,12 @@ impl TyExt for Ty {
                             .map(|pred| pred.clone().substitute(&Interner, &substs))
                             .filter(|wc| match &wc.skip_binders() {
                                 WhereClause::Implemented(tr) => {
-                                    tr.self_type_parameter(&Interner) == self
+                                    &tr.self_type_parameter(&Interner) == self
                                 }
                                 WhereClause::AliasEq(AliasEq {
                                     alias: AliasTy::Projection(proj),
                                     ty: _,
-                                }) => proj.self_type_parameter(&Interner) == self,
+                                }) => &proj.self_type_parameter(&Interner) == self,
                                 _ => false,
                             })
                             .collect::<Vec<_>>();
@@ -293,3 +293,13 @@ impl ProjectionTyExt for ProjectionTy {
         }
     }
 }
+
+pub trait TraitRefExt {
+    fn hir_trait_id(&self) -> TraitId;
+}
+
+impl TraitRefExt for TraitRef {
+    fn hir_trait_id(&self) -> TraitId {
+        from_chalk_trait_id(self.trait_id)
+    }
+}
diff --git a/crates/hir_ty/src/display.rs b/crates/hir_ty/src/display.rs
index 9e6bbcdf1..e0ca96c6d 100644
--- a/crates/hir_ty/src/display.rs
+++ b/crates/hir_ty/src/display.rs
@@ -24,7 +24,7 @@ use crate::{
     traits::chalk::from_chalk, utils::generics, AdtId, AliasEq, AliasTy, CallableDefId,
     CallableSig, Const, ConstValue, DomainGoal, GenericArg, ImplTraitId, Interner, Lifetime,
     LifetimeData, LifetimeOutlives, Mutability, OpaqueTy, ProjectionTy, ProjectionTyExt,
-    QuantifiedWhereClause, Scalar, TraitRef, Ty, TyExt, TyKind, WhereClause,
+    QuantifiedWhereClause, Scalar, TraitRef, TraitRefExt, Ty, TyExt, TyKind, WhereClause,
 };
 
 pub struct HirFormatter<'a> {
@@ -616,12 +616,12 @@ impl HirDisplay for Ty {
                                 .map(|pred| pred.clone().substitute(&Interner, &substs))
                                 .filter(|wc| match &wc.skip_binders() {
                                     WhereClause::Implemented(tr) => {
-                                        tr.self_type_parameter(&Interner) == self
+                                        &tr.self_type_parameter(&Interner) == self
                                     }
                                     WhereClause::AliasEq(AliasEq {
                                         alias: AliasTy::Projection(proj),
                                         ty: _,
-                                    }) => proj.self_type_parameter(&Interner) == self,
+                                    }) => &proj.self_type_parameter(&Interner) == self,
                                     _ => false,
                                 })
                                 .collect::<Vec<_>>();
@@ -745,7 +745,7 @@ fn write_bounds_like_dyn_trait(
                 // existential) here, which is the only thing that's
                 // possible in actual Rust, and hence don't print it
                 write!(f, "{}", f.db.trait_data(trait_).name)?;
-                if let [_, params @ ..] = &*trait_ref.substitution.interned() {
+                if let [_, params @ ..] = &*trait_ref.substitution.interned().as_slice() {
                     if is_fn_trait {
                         if let Some(args) =
                             params.first().and_then(|it| it.assert_ty_ref(&Interner).as_tuple())
@@ -792,31 +792,29 @@ fn write_bounds_like_dyn_trait(
     Ok(())
 }
 
-impl TraitRef {
-    fn hir_fmt_ext(&self, f: &mut HirFormatter, use_as: bool) -> Result<(), HirDisplayError> {
-        if f.should_truncate() {
-            return write!(f, "{}", TYPE_HINT_TRUNCATION);
-        }
+fn fmt_trait_ref(tr: &TraitRef, f: &mut HirFormatter, use_as: bool) -> Result<(), HirDisplayError> {
+    if f.should_truncate() {
+        return write!(f, "{}", TYPE_HINT_TRUNCATION);
+    }
 
-        self.self_type_parameter(&Interner).hir_fmt(f)?;
-        if use_as {
-            write!(f, " as ")?;
-        } else {
-            write!(f, ": ")?;
-        }
-        write!(f, "{}", f.db.trait_data(self.hir_trait_id()).name)?;
-        if self.substitution.len(&Interner) > 1 {
-            write!(f, "<")?;
-            f.write_joined(&self.substitution.interned()[1..], ", ")?;
-            write!(f, ">")?;
-        }
-        Ok(())
+    tr.self_type_parameter(&Interner).hir_fmt(f)?;
+    if use_as {
+        write!(f, " as ")?;
+    } else {
+        write!(f, ": ")?;
     }
+    write!(f, "{}", f.db.trait_data(tr.hir_trait_id()).name)?;
+    if tr.substitution.len(&Interner) > 1 {
+        write!(f, "<")?;
+        f.write_joined(&tr.substitution.interned()[1..], ", ")?;
+        write!(f, ">")?;
+    }
+    Ok(())
 }
 
 impl HirDisplay for TraitRef {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
-        self.hir_fmt_ext(f, false)
+        fmt_trait_ref(self, f, false)
     }
 }
 
@@ -830,7 +828,7 @@ impl HirDisplay for WhereClause {
             WhereClause::Implemented(trait_ref) => trait_ref.hir_fmt(f)?,
             WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
                 write!(f, "<")?;
-                projection_ty.trait_ref(f.db).hir_fmt_ext(f, true)?;
+                fmt_trait_ref(&projection_ty.trait_ref(f.db), f, true)?;
                 write!(
                     f,
                     ">::{} = ",
diff --git a/crates/hir_ty/src/infer.rs b/crates/hir_ty/src/infer.rs
index 6af0c59b8..531159e54 100644
--- a/crates/hir_ty/src/infer.rs
+++ b/crates/hir_ty/src/infer.rs
@@ -336,7 +336,7 @@ impl<'a> InferenceContext<'a> {
         self.last_obligations_check = Some(self.table.revision);
         let obligations = mem::replace(&mut self.obligations, Vec::new());
         for obligation in obligations {
-            let in_env = InEnvironment::new(self.trait_env.env.clone(), obligation.clone());
+            let in_env = InEnvironment::new(&self.trait_env.env, 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 f1af2a0bd..fd679f444 100644
--- a/crates/hir_ty/src/infer/coerce.rs
+++ b/crates/hir_ty/src/infer/coerce.rs
@@ -139,7 +139,7 @@ impl<'a> InferenceContext<'a> {
             b.push(from_ty.clone()).push(to_ty.clone()).build()
         };
 
-        let goal = InEnvironment::new(self.trait_env.env.clone(), trait_ref.cast(&Interner));
+        let goal = InEnvironment::new(&self.trait_env.env, trait_ref.cast(&Interner));
 
         let canonicalizer = self.canonicalizer();
         let canonicalized = canonicalizer.canonicalize_obligation(goal);
diff --git a/crates/hir_ty/src/infer/pat.rs b/crates/hir_ty/src/infer/pat.rs
index f88d5c5d3..a41e8e116 100644
--- a/crates/hir_ty/src/infer/pat.rs
+++ b/crates/hir_ty/src/infer/pat.rs
@@ -122,7 +122,7 @@ impl<'a> InferenceContext<'a> {
         let ty = match &body[pat] {
             &Pat::Tuple { ref args, ellipsis } => {
                 let expectations = match expected.as_tuple() {
-                    Some(parameters) => &*parameters.interned(),
+                    Some(parameters) => &*parameters.interned().as_slice(),
                     _ => &[],
                 };
 
diff --git a/crates/hir_ty/src/infer/path.rs b/crates/hir_ty/src/infer/path.rs
index b19d67bb1..f8955aa32 100644
--- a/crates/hir_ty/src/infer/path.rs
+++ b/crates/hir_ty/src/infer/path.rs
@@ -11,7 +11,8 @@ use hir_def::{
 use hir_expand::name::Name;
 
 use crate::{
-    method_resolution, Interner, Substitution, Ty, TyBuilder, TyExt, TyKind, ValueTyDefId,
+    method_resolution, Interner, Substitution, TraitRefExt, Ty, TyBuilder, TyExt, TyKind,
+    ValueTyDefId,
 };
 
 use super::{ExprOrPatId, InferenceContext, TraitRef};
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index 2e851d3e0..87f10e9d5 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -41,7 +41,7 @@ use crate::{db::HirDatabase, display::HirDisplay, utils::generics};
 
 pub use autoderef::autoderef;
 pub use builder::TyBuilder;
-pub use chalk_ext::{ProjectionTyExt, TyExt};
+pub use chalk_ext::*;
 pub use infer::{could_unify, InferenceResult};
 pub use lower::{
     associated_type_shorthand_candidates, callable_item_sig, CallableDefId, ImplTraitLoweringMode,
@@ -107,22 +107,18 @@ pub fn make_only_type_binders<T>(num_vars: usize, value: T) -> Binders<T> {
     )
 }
 
-impl TraitRef {
-    pub fn hir_trait_id(&self) -> TraitId {
-        from_chalk_trait_id(self.trait_id)
-    }
-}
-
-impl<T> Canonical<T> {
-    pub fn new(value: T, kinds: impl IntoIterator<Item = TyVariableKind>) -> Self {
-        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) }
-    }
+// FIXME: get rid of this
+pub fn make_canonical<T>(
+    value: T,
+    kinds: impl IntoIterator<Item = TyVariableKind>,
+) -> Canonical<T> {
+    let kinds = kinds.into_iter().map(|tk| {
+        chalk_ir::CanonicalVarKind::new(
+            chalk_ir::VariableKind::Ty(tk),
+            chalk_ir::UniverseIndex::ROOT,
+        )
+    });
+    Canonical { value, binders: chalk_ir::CanonicalVarKinds::from_iter(&Interner, kinds) }
 }
 
 /// A function signature as seen by type inference: Several parameter types and
diff --git a/crates/hir_ty/src/lower.rs b/crates/hir_ty/src/lower.rs
index 4ca6aa538..e6903e189 100644
--- a/crates/hir_ty/src/lower.rs
+++ b/crates/hir_ty/src/lower.rs
@@ -35,7 +35,7 @@ use crate::{
     AliasEq, AliasTy, Binders, BoundVar, CallableSig, DebruijnIndex, DynTy, FnPointer, FnSig,
     FnSubst, ImplTraitId, OpaqueTy, PolyFnSig, ProjectionTy, QuantifiedWhereClause,
     QuantifiedWhereClauses, ReturnTypeImplTrait, ReturnTypeImplTraits, Substitution,
-    TraitEnvironment, TraitRef, Ty, TyBuilder, TyKind, TypeWalk, WhereClause,
+    TraitEnvironment, TraitRef, TraitRefExt, Ty, TyBuilder, TyKind, TypeWalk, WhereClause,
 };
 
 #[derive(Debug)]
diff --git a/crates/hir_ty/src/method_resolution.rs b/crates/hir_ty/src/method_resolution.rs
index c601f2d53..7e09a1539 100644
--- a/crates/hir_ty/src/method_resolution.rs
+++ b/crates/hir_ty/src/method_resolution.rs
@@ -22,8 +22,8 @@ use crate::{
     static_lifetime,
     utils::all_super_traits,
     AdtId, Canonical, CanonicalVarKinds, DebruijnIndex, FnPointer, FnSig, ForeignDefId,
-    InEnvironment, Interner, Scalar, Substitution, TraitEnvironment, Ty, TyBuilder, TyExt, TyKind,
-    TypeWalk,
+    InEnvironment, Interner, Scalar, Substitution, TraitEnvironment, TraitRefExt, Ty, TyBuilder,
+    TyExt, TyKind, TypeWalk,
 };
 
 /// This is used as a key for indexing impls.
@@ -845,7 +845,7 @@ fn generic_implements_goal(
     let obligation = trait_ref.cast(&Interner);
     Canonical {
         binders: CanonicalVarKinds::from_iter(&Interner, kinds),
-        value: InEnvironment::new(env.env.clone(), obligation),
+        value: InEnvironment::new(&env.env, obligation),
     }
 }
 
diff --git a/crates/hir_ty/src/traits.rs b/crates/hir_ty/src/traits.rs
index 3374532c3..7d87741b8 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, Ty, TyKind, WhereClause,
+    Solution, TraitRefExt, Ty, TyKind, WhereClause,
 };
 
 use self::chalk::{from_chalk, Interner, ToChalk};
diff --git a/crates/hir_ty/src/traits/chalk.rs b/crates/hir_ty/src/traits/chalk.rs
index f03b92422..090f6492b 100644
--- a/crates/hir_ty/src/traits/chalk.rs
+++ b/crates/hir_ty/src/traits/chalk.rs
@@ -22,7 +22,7 @@ use crate::{
     to_assoc_type_id, to_chalk_trait_id,
     utils::generics,
     AliasEq, AliasTy, BoundVar, CallableDefId, DebruijnIndex, FnDefId, ProjectionTy, Substitution,
-    TraitRef, Ty, TyBuilder, TyExt, TyKind, WhereClause,
+    TraitRef, TraitRefExt, Ty, TyBuilder, TyExt, TyKind, WhereClause,
 };
 use mapping::{
     convert_where_clauses, generic_predicate_to_inline_bound, make_binders, TypeAliasAsValue,
diff --git a/crates/hir_ty/src/traits/chalk/mapping.rs b/crates/hir_ty/src/traits/chalk/mapping.rs
index 84abd99b2..701359e6f 100644
--- a/crates/hir_ty/src/traits/chalk/mapping.rs
+++ b/crates/hir_ty/src/traits/chalk/mapping.rs
@@ -10,9 +10,9 @@ use base_db::salsa::InternKey;
 use hir_def::{GenericDefId, TypeAliasId};
 
 use crate::{
-    chalk_ext::ProjectionTyExt, db::HirDatabase, static_lifetime, AliasTy, CallableDefId,
-    Canonical, ConstrainedSubst, DomainGoal, FnPointer, GenericArg, InEnvironment, OpaqueTy,
-    ProjectionTy, QuantifiedWhereClause, Substitution, TraitRef, Ty, TypeWalk, WhereClause,
+    db::HirDatabase, static_lifetime, AliasTy, CallableDefId, Canonical, ConstrainedSubst,
+    DomainGoal, FnPointer, GenericArg, InEnvironment, OpaqueTy, ProjectionTy, ProjectionTyExt,
+    QuantifiedWhereClause, Substitution, TraitRef, Ty, TypeWalk, WhereClause,
 };
 
 use super::interner::*;
@@ -509,7 +509,7 @@ pub(super) fn generic_predicate_to_inline_bound(
     let (pred, binders) = pred.as_ref().into_value_and_skipped_binders();
     match pred {
         WhereClause::Implemented(trait_ref) => {
-            if trait_ref.self_type_parameter(&Interner) != &self_ty_shifted_in {
+            if trait_ref.self_type_parameter(&Interner) != self_ty_shifted_in {
                 // we can only convert predicates back to type bounds if they
                 // have the expected self type
                 return None;
@@ -522,7 +522,7 @@ pub(super) fn generic_predicate_to_inline_bound(
             Some(chalk_ir::Binders::new(binders, rust_ir::InlineBound::TraitBound(trait_bound)))
         }
         WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
-            if projection_ty.self_type_parameter(&Interner) != &self_ty_shifted_in {
+            if projection_ty.self_type_parameter(&Interner) != self_ty_shifted_in {
                 return None;
             }
             let trait_ = projection_ty.trait_(db);
diff --git a/crates/hir_ty/src/types.rs b/crates/hir_ty/src/types.rs
index c25bc2d6a..89adad108 100644
--- a/crates/hir_ty/src/types.rs
+++ b/crates/hir_ty/src/types.rs
@@ -30,8 +30,8 @@ pub struct ProjectionTy {
 }
 
 impl ProjectionTy {
-    pub fn self_type_parameter(&self, interner: &Interner) -> &Ty {
-        &self.substitution.interned()[0].assert_ty_ref(interner)
+    pub fn self_type_parameter(&self, interner: &Interner) -> Ty {
+        self.substitution.interned()[0].assert_ty_ref(interner).clone()
     }
 }
 
@@ -282,7 +282,7 @@ impl GenericArg {
 pub struct Substitution(SmallVec<[GenericArg; 2]>);
 
 impl Substitution {
-    pub fn interned(&self) -> &[GenericArg] {
+    pub fn interned(&self) -> &SmallVec<[GenericArg; 2]> {
         &self.0
     }
 
@@ -413,8 +413,8 @@ pub struct TraitRef {
 }
 
 impl TraitRef {
-    pub fn self_type_parameter(&self, interner: &Interner) -> &Ty {
-        &self.substitution.at(interner, 0).assert_ty_ref(interner)
+    pub fn self_type_parameter(&self, interner: &Interner) -> Ty {
+        self.substitution.at(interner, 0).assert_ty_ref(interner).clone()
     }
 }
 
@@ -470,8 +470,8 @@ pub struct InEnvironment<T> {
 }
 
 impl<T> InEnvironment<T> {
-    pub fn new(environment: chalk_ir::Environment<Interner>, value: T) -> InEnvironment<T> {
-        InEnvironment { environment, goal: value }
+    pub fn new(environment: &chalk_ir::Environment<Interner>, value: T) -> InEnvironment<T> {
+        InEnvironment { environment: environment.clone(), goal: value }
     }
 }
 
diff --git a/crates/hir_ty/src/utils.rs b/crates/hir_ty/src/utils.rs
index 0a424f607..8d5d5cd73 100644
--- a/crates/hir_ty/src/utils.rs
+++ b/crates/hir_ty/src/utils.rs
@@ -16,7 +16,9 @@ use hir_def::{
 };
 use hir_expand::name::{name, Name};
 
-use crate::{db::HirDatabase, Interner, Substitution, TraitRef, TyKind, TypeWalk, WhereClause};
+use crate::{
+    db::HirDatabase, Interner, Substitution, TraitRef, TraitRefExt, TyKind, TypeWalk, WhereClause,
+};
 
 fn direct_super_traits(db: &dyn DefDatabase, trait_: TraitId) -> Vec<TraitId> {
     let resolver = trait_.resolver(db);