5 files changed, 52 insertions, 63 deletions

diff --git a/crates/ra_hir_ty/src/db.rs b/crates/ra_hir_ty/src/db.rs
index 7684ade06..21ab22fa9 100644
--- a/crates/ra_hir_ty/src/db.rs
+++ b/crates/ra_hir_ty/src/db.rs
@@ -50,10 +50,10 @@ pub trait HirDatabase: DefDatabase {
     fn generic_predicates_for_param(
         &self,
         param_id: TypeParamId,
-    ) -> Arc<[GenericPredicate]>;
+    ) -> Arc<[Binders<GenericPredicate>]>;
 
     #[salsa::invoke(crate::lower::generic_predicates_query)]
-    fn generic_predicates(&self, def: GenericDefId) -> Arc<[GenericPredicate]>;
+    fn generic_predicates(&self, def: GenericDefId) -> Arc<[Binders<GenericPredicate>]>;
 
     #[salsa::invoke(crate::lower::generic_defaults_query)]
     fn generic_defaults(&self, def: GenericDefId) -> Substs;
diff --git a/crates/ra_hir_ty/src/infer/expr.rs b/crates/ra_hir_ty/src/infer/expr.rs
index b32df8e90..b69785e55 100644
--- a/crates/ra_hir_ty/src/infer/expr.rs
+++ b/crates/ra_hir_ty/src/infer/expr.rs
@@ -20,7 +20,7 @@ use crate::{
     traits::InEnvironment,
     utils::{generics, variant_data, Generics},
     ApplicationTy, CallableDef, InferTy, IntTy, Mutability, Obligation, Substs, TraitRef, Ty,
-    TypeCtor, TypeWalk, Uncertain, Binders,
+    TypeCtor, Uncertain, Binders,
 };
 
 use super::{BindingMode, Expectation, InferenceContext, InferenceDiagnostic, TypeMismatch};
@@ -686,7 +686,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             if let TypeCtor::FnDef(def) = a_ty.ctor {
                 let generic_predicates = self.db.generic_predicates(def.into());
                 for predicate in generic_predicates.iter() {
-                    let predicate = predicate.clone().subst_type_params(self.db, def.into(), &a_ty.parameters);
+                    let predicate = predicate.clone().subst(&a_ty.parameters);
                     if let Some(obligation) = Obligation::from_predicate(predicate) {
                         self.obligations.push(obligation);
                     }
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index 1da4bcc19..a685e70c2 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -749,28 +749,7 @@ pub trait TypeWalk {
         self
     }
 
-    /// Replaces type parameters in this type using the given `Substs`. (So e.g.
-    /// if `self` is `&[T]`, where type parameter T has index 0, and the
-    /// `Substs` contain `u32` at index 0, we'll have `&[u32]` afterwards.)
-    // TODO: this should mostly not be used anymore
-    fn subst_type_params(self, db: &impl HirDatabase, def: GenericDefId, substs: &Substs) -> Self
-    where
-        Self: Sized,
-    {
-        let generics = generics(db, def);
-        self.fold(&mut |ty| match ty {
-            Ty::Param(id) => {
-                if let Some(idx) = generics.param_idx(id) {
-                    substs.get(idx as usize).cloned().unwrap_or(Ty::Param(id))
-                } else {
-                    ty
-                }
-            }
-            ty => ty,
-        })
-    }
-
-    /// Substitutes `Ty::Bound` vars (as opposed to type parameters).
+    /// Substitutes `Ty::Bound` vars with the given substitution.
     fn subst_bound_vars(mut self, substs: &Substs) -> Self
     where
         Self: Sized,
@@ -1045,9 +1024,10 @@ impl HirDisplay for Ty {
                         write!(f, "{}", param_data.name.clone().unwrap_or_else(Name::missing))?
                     }
                     TypeParamProvenance::ArgumentImplTrait => {
-                        let bounds = f.db.generic_predicates_for_param(*id);
                         write!(f, "impl ")?;
-                        write_bounds_like_dyn_trait(&bounds, f)?;
+                        let bounds = f.db.generic_predicates_for_param(*id);
+                        let substs = Substs::type_params(&generics);
+                        write_bounds_like_dyn_trait(&bounds.iter().map(|b| b.clone().subst(&substs)).collect::<Vec<_>>(), f)?;
                     }
                 }
             }
diff --git a/crates/ra_hir_ty/src/lower.rs b/crates/ra_hir_ty/src/lower.rs
index 76e2fbabf..847111748 100644
--- a/crates/ra_hir_ty/src/lower.rs
+++ b/crates/ra_hir_ty/src/lower.rs
@@ -10,13 +10,13 @@ use std::sync::Arc;
 
 use hir_def::{
     builtin_type::BuiltinType,
-    generics::{WherePredicate, WherePredicateTarget, TypeParamProvenance},
+    generics::{TypeParamProvenance, WherePredicate, WherePredicateTarget},
     path::{GenericArg, Path, PathSegment, PathSegments},
     resolver::{HasResolver, Resolver, TypeNs},
     type_ref::{TypeBound, TypeRef},
     AdtId, ConstId, EnumId, EnumVariantId, FunctionId, GenericDefId, HasModule, ImplId,
-    LocalStructFieldId, Lookup, StaticId, StructId, TraitId, TypeAliasId, UnionId, VariantId,
-    TypeParamId
+    LocalStructFieldId, Lookup, StaticId, StructId, TraitId, TypeAliasId, TypeParamId, UnionId,
+    VariantId,
 };
 use ra_arena::map::ArenaMap;
 use ra_db::CrateId;
@@ -148,7 +148,9 @@ impl Ty {
                             let generics = generics(ctx.db, def);
                             let param = generics
                                 .iter()
-                                .filter(|(_, data)| data.provenance == TypeParamProvenance::ArgumentImplTrait)
+                                .filter(|(_, data)| {
+                                    data.provenance == TypeParamProvenance::ArgumentImplTrait
+                                })
                                 .nth(idx as usize)
                                 .map_or(Ty::Unknown, |(id, _)| Ty::Param(id));
                             param
@@ -338,19 +340,12 @@ impl Ty {
                     return Ty::Unknown;
                 };
                 param_id
-            },
+            }
             _ => return Ty::Unknown, // Error: Ambiguous associated type
         };
         let predicates = ctx.db.generic_predicates_for_param(param_id);
-        let traits_from_env = predicates.iter().filter_map(|pred| match pred {
-            GenericPredicate::Implemented(tr) => {
-                if let Ty::Param(id) = tr.self_ty() {
-                    if *id == param_id {
-                        return Some(tr.trait_);
-                    }
-                }
-                None
-            }
+        let traits_from_env = predicates.iter().filter_map(|pred| match &pred.value {
+            GenericPredicate::Implemented(tr) => Some(tr.trait_),
             _ => None,
         });
         let traits = traits_from_env.flat_map(|t| all_super_traits(ctx.db, t));
@@ -620,8 +615,8 @@ pub(crate) fn field_types_query(
     };
     let generics = generics(db, def);
     let mut res = ArenaMap::default();
-    let ctx = TyLoweringContext::new(db, &resolver)
-        .with_type_param_mode(TypeParamLoweringMode::Variable);
+    let ctx =
+        TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     for (field_id, field_data) in var_data.fields().iter() {
         res.insert(field_id, Binders::new(generics.len(), Ty::from_hir(&ctx, &field_data.type_ref)))
     }
@@ -639,10 +634,11 @@ pub(crate) fn field_types_query(
 pub(crate) fn generic_predicates_for_param_query(
     db: &impl HirDatabase,
     param_id: TypeParamId,
-) -> Arc<[GenericPredicate]> {
+) -> Arc<[Binders<GenericPredicate>]> {
     let resolver = param_id.parent.resolver(db);
-    let ctx = TyLoweringContext::new(db, &resolver);
-    // let generics = generics(db, def);
+    let ctx =
+        TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
+    let generics = generics(db, param_id.parent);
     resolver
         .where_predicates_in_scope()
         // we have to filter out all other predicates *first*, before attempting to lower them
@@ -650,11 +646,12 @@ pub(crate) fn generic_predicates_for_param_query(
             WherePredicateTarget::TypeRef(type_ref) => {
                 Ty::from_hir_only_param(&ctx, type_ref) == Some(param_id)
             }
-            WherePredicateTarget::TypeParam(local_id) => {
-                *local_id == param_id.local_id
-            }
+            WherePredicateTarget::TypeParam(local_id) => *local_id == param_id.local_id,
+        })
+        .flat_map(|pred| {
+            GenericPredicate::from_where_predicate(&ctx, pred)
+                .map(|p| Binders::new(generics.len(), p))
         })
-        .flat_map(|pred| GenericPredicate::from_where_predicate(&ctx, pred))
         .collect()
 }
 
@@ -662,13 +659,14 @@ pub(crate) fn generic_predicates_for_param_recover(
     _db: &impl HirDatabase,
     _cycle: &[String],
     _param_id: &TypeParamId,
-) -> Arc<[GenericPredicate]> {
+) -> Arc<[Binders<GenericPredicate>]> {
     Arc::new([])
 }
 
 impl TraitEnvironment {
     pub fn lower(db: &impl HirDatabase, resolver: &Resolver) -> Arc<TraitEnvironment> {
-        let ctx = TyLoweringContext::new(db, &resolver);
+        let ctx = TyLoweringContext::new(db, &resolver)
+            .with_type_param_mode(TypeParamLoweringMode::Placeholder);
         let predicates = resolver
             .where_predicates_in_scope()
             .flat_map(|pred| GenericPredicate::from_where_predicate(&ctx, pred))
@@ -682,12 +680,17 @@ impl TraitEnvironment {
 pub(crate) fn generic_predicates_query(
     db: &impl HirDatabase,
     def: GenericDefId,
-) -> Arc<[GenericPredicate]> {
+) -> Arc<[Binders<GenericPredicate>]> {
     let resolver = def.resolver(db);
-    let ctx = TyLoweringContext::new(db, &resolver);
+    let ctx =
+        TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
+    let generics = generics(db, def);
     resolver
         .where_predicates_in_scope()
-        .flat_map(|pred| GenericPredicate::from_where_predicate(&ctx, pred))
+        .flat_map(|pred| {
+            GenericPredicate::from_where_predicate(&ctx, pred)
+                .map(|p| Binders::new(generics.len(), p))
+        })
         .collect()
 }
 
@@ -915,12 +918,18 @@ pub(crate) fn impl_self_ty_recover(
     Binders::new(generics.len(), Ty::Unknown)
 }
 
-pub(crate) fn impl_trait_query(db: &impl HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
+pub(crate) fn impl_trait_query(
+    db: &impl HirDatabase,
+    impl_id: ImplId,
+) -> Option<Binders<TraitRef>> {
     let impl_data = db.impl_data(impl_id);
     let resolver = impl_id.resolver(db);
-    let ctx = TyLoweringContext::new(db, &resolver)
-        .with_type_param_mode(TypeParamLoweringMode::Variable);
+    let ctx =
+        TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     let self_ty = db.impl_self_ty(impl_id);
     let target_trait = impl_data.target_trait.as_ref()?;
-    Some(Binders::new(self_ty.num_binders, TraitRef::from_hir(&ctx, target_trait, Some(self_ty.value.clone()))?))
+    Some(Binders::new(
+        self_ty.num_binders,
+        TraitRef::from_hir(&ctx, target_trait, Some(self_ty.value.clone()))?,
+    ))
 }
diff --git a/crates/ra_hir_ty/src/traits/chalk.rs b/crates/ra_hir_ty/src/traits/chalk.rs
index 6e97f7dd2..8260bd157 100644
--- a/crates/ra_hir_ty/src/traits/chalk.rs
+++ b/crates/ra_hir_ty/src/traits/chalk.rs
@@ -14,7 +14,7 @@ use ra_db::{
 use super::{builtin, AssocTyValue, Canonical, ChalkContext, Impl, Obligation};
 use crate::{
     db::HirDatabase, display::HirDisplay, utils::generics, ApplicationTy, GenericPredicate,
-    ProjectionTy, Substs, TraitRef, Ty, TypeCtor, TypeWalk,
+    ProjectionTy, Substs, TraitRef, Ty, TypeCtor,
 };
 
 #[derive(Debug, Copy, Clone, Hash, PartialOrd, Ord, PartialEq, Eq)]
@@ -522,11 +522,11 @@ fn convert_where_clauses(
     let generic_predicates = db.generic_predicates(def);
     let mut result = Vec::with_capacity(generic_predicates.len());
     for pred in generic_predicates.iter() {
-        if pred.is_error() {
+        if pred.value.is_error() {
             // skip errored predicates completely
             continue;
         }
-        result.push(pred.clone().subst_type_params(db, def, substs).to_chalk(db));
+        result.push(pred.clone().subst(substs).to_chalk(db));
     }
     result
 }