1 files changed, 33 insertions, 30 deletions

diff --git a/crates/hir_ty/src/autoderef.rs b/crates/hir_ty/src/autoderef.rs
index dc5fc759a..f8e9db9ae 100644
--- a/crates/hir_ty/src/autoderef.rs
+++ b/crates/hir_ty/src/autoderef.rs
@@ -12,12 +12,8 @@ use hir_expand::name::name;
 use log::{info, warn};
 
 use crate::{
-    db::HirDatabase,
-    to_assoc_type_id, to_chalk_trait_id,
-    traits::{InEnvironment, Solution},
-    utils::generics,
-    AliasEq, AliasTy, BoundVar, Canonical, CanonicalVarKinds, DebruijnIndex, Interner,
-    ProjectionTy, Substitution, TraitRef, Ty, TyKind,
+    db::HirDatabase, AliasEq, AliasTy, BoundVar, Canonical, CanonicalVarKinds, DebruijnIndex,
+    InEnvironment, Interner, ProjectionTyExt, Solution, Ty, TyBuilder, TyKind,
 };
 
 const AUTODEREF_RECURSION_LIMIT: usize = 10;
@@ -39,13 +35,21 @@ pub(crate) fn deref(
     krate: CrateId,
     ty: InEnvironment<&Canonical<Ty>>,
 ) -> Option<Canonical<Ty>> {
-    if let Some(derefed) = ty.goal.value.builtin_deref() {
+    if let Some(derefed) = builtin_deref(&ty.goal.value) {
         Some(Canonical { value: derefed, binders: ty.goal.binders.clone() })
     } else {
         deref_by_trait(db, krate, ty)
     }
 }
 
+fn builtin_deref(ty: &Ty) -> Option<Ty> {
+    match ty.kind(&Interner) {
+        TyKind::Ref(.., ty) => Some(ty.clone()),
+        TyKind::Raw(.., ty) => Some(ty.clone()),
+        _ => None,
+    }
+}
+
 fn deref_by_trait(
     db: &dyn HirDatabase,
     krate: CrateId,
@@ -57,21 +61,20 @@ fn deref_by_trait(
     };
     let target = db.trait_data(deref_trait).associated_type_by_name(&name![Target])?;
 
-    let generic_params = generics(db.upcast(), target.into());
-    if generic_params.len() != 1 {
-        // the Target type + Deref trait should only have one generic parameter,
-        // namely Deref's Self type
-        return None;
-    }
+    let projection = {
+        let b = TyBuilder::assoc_type_projection(db, target);
+        if b.remaining() != 1 {
+            // the Target type + Deref trait should only have one generic parameter,
+            // namely Deref's Self type
+            return None;
+        }
+        b.push(ty.goal.value.clone()).build()
+    };
 
     // FIXME make the Canonical / bound var handling nicer
 
-    let parameters =
-        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 trait_ref = projection.trait_ref(db);
     let implements_goal = Canonical {
         binders: ty.goal.binders.clone(),
         value: InEnvironment {
@@ -84,11 +87,8 @@ fn deref_by_trait(
     }
 
     // Now do the assoc type projection
-    let projection = AliasEq {
-        alias: AliasTy::Projection(ProjectionTy {
-            associated_ty_id: to_assoc_type_id(target),
-            substitution: parameters,
-        }),
+    let alias_eq = AliasEq {
+        alias: AliasTy::Projection(projection),
         ty: TyKind::BoundVar(BoundVar::new(
             DebruijnIndex::INNERMOST,
             ty.goal.binders.len(&Interner),
@@ -96,9 +96,7 @@ fn deref_by_trait(
         .intern(&Interner),
     };
 
-    let obligation = projection.cast(&Interner);
-
-    let in_env = InEnvironment { goal: obligation, environment: ty.environment };
+    let in_env = InEnvironment { goal: alias_eq.cast(&Interner), environment: ty.environment };
 
     let canonical = Canonical {
         value: in_env,
@@ -130,8 +128,8 @@ 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[i - 1].interned(&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);
@@ -139,8 +137,13 @@ fn deref_by_trait(
                 }
             }
             Some(Canonical {
-                value: vars.0.value[vars.0.value.len() - 1].clone(),
-                binders: vars.0.binders.clone(),
+                value: vars
+                    .value
+                    .subst
+                    .at(&Interner, vars.value.subst.len(&Interner) - 1)
+                    .assert_ty_ref(&Interner)
+                    .clone(),
+                binders: vars.binders.clone(),
             })
         }
         Solution::Ambig(_) => {