12 files changed, 310 insertions, 334 deletions

diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index 821f919d4..c5cf39ee1 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -9,7 +9,7 @@ use hir_def::{
     builtin_type::BuiltinType,
     docs::Documentation,
     per_ns::PerNs,
-    resolver::{HasResolver, TypeNs},
+    resolver::HasResolver,
     type_ref::{Mutability, TypeRef},
     AdtId, AstItemDef, ConstId, ContainerId, DefWithBodyId, EnumId, FunctionId, GenericDefId,
     HasModule, ImplId, LocalEnumVariantId, LocalImportId, LocalModuleId, LocalStructFieldId,
@@ -28,8 +28,7 @@ use crate::{
     expr::{BindingAnnotation, Body, BodySourceMap, ExprValidator, Pat, PatId},
     ty::display::HirFormatter,
     ty::{
-        self, InEnvironment, InferenceResult, Namespace, TraitEnvironment, TraitRef, Ty, TypeCtor,
-        TypeWalk,
+        self, InEnvironment, InferenceResult, TraitEnvironment, TraitRef, Ty, TypeCtor, TypeWalk,
     },
     CallableDef, Either, HirDisplay, Name, Source,
 };
@@ -354,11 +353,11 @@ impl Struct {
     }
 
     pub fn ty(self, db: &impl HirDatabase) -> Ty {
-        db.type_for_def(self.into(), Namespace::Types)
+        db.ty(self.id.into())
     }
 
     pub fn constructor_ty(self, db: &impl HirDatabase) -> Ty {
-        db.type_for_def(self.into(), Namespace::Values)
+        db.value_ty(self.id.into())
     }
 
     fn variant_data(self, db: &impl DefDatabase) -> Arc<VariantData> {
@@ -381,7 +380,7 @@ impl Union {
     }
 
     pub fn ty(self, db: &impl HirDatabase) -> Ty {
-        db.type_for_def(self.into(), Namespace::Types)
+        db.ty(self.id.into())
     }
 
     pub fn fields(self, db: &impl HirDatabase) -> Vec<StructField> {
@@ -442,7 +441,7 @@ impl Enum {
     }
 
     pub fn ty(self, db: &impl HirDatabase) -> Ty {
-        db.type_for_def(self.into(), Namespace::Types)
+        db.ty(self.id.into())
     }
 }
 
@@ -617,7 +616,7 @@ impl Function {
     }
 
     pub fn ty(self, db: &impl HirDatabase) -> Ty {
-        db.type_for_def(self.into(), Namespace::Values)
+        db.value_ty(self.id.into())
     }
 
     pub fn infer(self, db: &impl HirDatabase) -> Arc<InferenceResult> {
@@ -737,68 +736,11 @@ impl Trait {
     }
 
     pub fn items(self, db: &impl DefDatabase) -> Vec<AssocItem> {
-        db.trait_data(self.id).items.iter().map(|it| (*it).into()).collect()
-    }
-
-    fn direct_super_traits(self, db: &impl HirDatabase) -> Vec<Trait> {
-        let resolver = self.id.resolver(db);
-        // returning the iterator directly doesn't easily work because of
-        // lifetime problems, but since there usually shouldn't be more than a
-        // few direct traits this should be fine (we could even use some kind of
-        // SmallVec if performance is a concern)
-        db.generic_params(self.id.into())
-            .where_predicates
-            .iter()
-            .filter_map(|pred| match &pred.type_ref {
-                TypeRef::Path(p) if p.as_ident() == Some(&name::SELF_TYPE) => pred.bound.as_path(),
-                _ => None,
-            })
-            .filter_map(|path| match resolver.resolve_path_in_type_ns_fully(db, path) {
-                Some(TypeNs::TraitId(t)) => Some(t),
-                _ => None,
-            })
-            .map(Trait::from)
-            .collect()
-    }
-
-    /// Returns an iterator over the whole super trait hierarchy (including the
-    /// trait itself).
-    pub fn all_super_traits(self, db: &impl HirDatabase) -> Vec<Trait> {
-        // we need to take care a bit here to avoid infinite loops in case of cycles
-        // (i.e. if we have `trait A: B; trait B: A;`)
-        let mut result = vec![self];
-        let mut i = 0;
-        while i < result.len() {
-            let t = result[i];
-            // yeah this is quadratic, but trait hierarchies should be flat
-            // enough that this doesn't matter
-            for tt in t.direct_super_traits(db) {
-                if !result.contains(&tt) {
-                    result.push(tt);
-                }
-            }
-            i += 1;
-        }
-        result
-    }
-
-    pub fn associated_type_by_name(self, db: &impl DefDatabase, name: &Name) -> Option<TypeAlias> {
-        let trait_data = db.trait_data(self.id);
-        let res =
-            trait_data.associated_types().map(TypeAlias::from).find(|t| &t.name(db) == name)?;
-        Some(res)
-    }
-
-    pub fn associated_type_by_name_including_super_traits(
-        self,
-        db: &impl HirDatabase,
-        name: &Name,
-    ) -> Option<TypeAlias> {
-        self.all_super_traits(db).into_iter().find_map(|t| t.associated_type_by_name(db, name))
+        db.trait_data(self.id).items.iter().map(|(_name, it)| (*it).into()).collect()
     }
 
     pub fn trait_ref(self, db: &impl HirDatabase) -> TraitRef {
-        TraitRef::for_trait(db, self)
+        TraitRef::for_trait(db, self.id)
     }
 
     pub fn is_auto(self, db: &impl DefDatabase) -> bool {
@@ -854,7 +796,7 @@ impl TypeAlias {
     }
 
     pub fn ty(self, db: &impl HirDatabase) -> Ty {
-        db.type_for_def(self.into(), Namespace::Types)
+        db.ty(self.id.into())
     }
 
     pub fn name(self, db: &impl DefDatabase) -> Name {
diff --git a/crates/ra_hir/src/db.rs b/crates/ra_hir/src/db.rs
index 32f05a4d8..3b5aa7516 100644
--- a/crates/ra_hir/src/db.rs
+++ b/crates/ra_hir/src/db.rs
@@ -9,8 +9,8 @@ use crate::{
     ty::{
         method_resolution::CrateImplBlocks,
         traits::{AssocTyValue, Impl},
-        CallableDef, FnSig, GenericPredicate, InferenceResult, Namespace, Substs, Ty, TypableDef,
-        TypeCtor,
+        CallableDef, FnSig, GenericPredicate, InferenceResult, Substs, Ty, TyDefId, TypeCtor,
+        ValueTyDefId,
     },
     Crate, DefWithBody, ImplBlock, Trait,
 };
@@ -37,8 +37,11 @@ pub trait HirDatabase: DefDatabase {
     #[salsa::invoke(crate::ty::infer_query)]
     fn infer(&self, def: DefWithBody) -> Arc<InferenceResult>;
 
-    #[salsa::invoke(crate::ty::type_for_def)]
-    fn type_for_def(&self, def: TypableDef, ns: Namespace) -> Ty;
+    #[salsa::invoke(crate::ty::ty_query)]
+    fn ty(&self, def: TyDefId) -> Ty;
+
+    #[salsa::invoke(crate::ty::value_ty_query)]
+    fn value_ty(&self, def: ValueTyDefId) -> Ty;
 
     #[salsa::invoke(crate::ty::field_types_query)]
     fn field_types(&self, var: VariantId) -> Arc<ArenaMap<LocalStructFieldId, Ty>>;
diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index bd03055b9..680ddc2f9 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -9,6 +9,7 @@ mod op;
 mod lower;
 mod infer;
 pub(crate) mod display;
+pub(crate) mod utils;
 
 #[cfg(test)]
 mod tests;
@@ -18,14 +19,16 @@ use std::sync::Arc;
 use std::{fmt, iter, mem};
 
 use hir_def::{
-    generics::GenericParams, AdtId, ContainerId, DefWithBodyId, GenericDefId, HasModule, Lookup,
-    TraitId, TypeAliasId,
+    expr::ExprId, generics::GenericParams, type_ref::Mutability, AdtId, ContainerId, DefWithBodyId,
+    GenericDefId, HasModule, Lookup, TraitId, TypeAliasId,
 };
 use ra_db::{impl_intern_key, salsa};
 
 use crate::{
-    db::HirDatabase, expr::ExprId, util::make_mut_slice, Adt, Crate, FloatTy, IntTy, Mutability,
-    Name, Trait, Uncertain,
+    db::HirDatabase,
+    ty::primitive::{FloatTy, IntTy, Uncertain},
+    util::make_mut_slice,
+    Adt, Crate, Name,
 };
 use display::{HirDisplay, HirFormatter};
 
@@ -34,8 +37,8 @@ pub(crate) use infer::{infer_query, InferTy, InferenceResult};
 pub use lower::CallableDef;
 pub(crate) use lower::{
     callable_item_sig, field_types_query, generic_defaults_query,
-    generic_predicates_for_param_query, generic_predicates_query, type_for_def, Namespace,
-    TypableDef,
+    generic_predicates_for_param_query, generic_predicates_query, ty_query, value_ty_query,
+    TyDefId, TypableDef, ValueTyDefId,
 };
 pub(crate) use traits::{InEnvironment, Obligation, ProjectionPredicate, TraitEnvironment};
 
@@ -444,7 +447,7 @@ impl Deref for Substs {
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub struct TraitRef {
     /// FIXME name?
-    pub trait_: Trait,
+    pub trait_: TraitId,
     pub substs: Substs,
 }
 
@@ -675,7 +678,7 @@ impl Ty {
     }
 
     /// If this is an `impl Trait` or `dyn Trait`, returns that trait.
-    pub fn inherent_trait(&self) -> Option<Trait> {
+    pub fn inherent_trait(&self) -> Option<TraitId> {
         match self {
             Ty::Dyn(predicates) | Ty::Opaque(predicates) => {
                 predicates.iter().find_map(|pred| match pred {
@@ -987,7 +990,10 @@ impl HirDisplay for Ty {
                             write!(
                                 f,
                                 "{}",
-                                trait_ref.trait_.name(f.db).unwrap_or_else(Name::missing)
+                                f.db.trait_data(trait_ref.trait_)
+                                    .name
+                                    .clone()
+                                    .unwrap_or_else(Name::missing)
                             )?;
                             if trait_ref.substs.len() > 1 {
                                 write!(f, "<")?;
@@ -1048,7 +1054,7 @@ impl TraitRef {
         } else {
             write!(f, ": ")?;
         }
-        write!(f, "{}", self.trait_.name(f.db).unwrap_or_else(Name::missing))?;
+        write!(f, "{}", f.db.trait_data(self.trait_).name.clone().unwrap_or_else(Name::missing))?;
         if self.substs.len() > 1 {
             write!(f, "<")?;
             f.write_joined(&self.substs[1..], ", ")?;
diff --git a/crates/ra_hir/src/ty/autoderef.rs b/crates/ra_hir/src/ty/autoderef.rs
index 9e7593b8b..ae68234ac 100644
--- a/crates/ra_hir/src/ty/autoderef.rs
+++ b/crates/ra_hir/src/ty/autoderef.rs
@@ -10,7 +10,7 @@ use hir_expand::name;
 use log::{info, warn};
 use ra_db::CrateId;
 
-use crate::{db::HirDatabase, Trait};
+use crate::db::HirDatabase;
 
 use super::{
     traits::{InEnvironment, Solution},
@@ -49,12 +49,12 @@ fn deref_by_trait(
     ty: InEnvironment<&Canonical<Ty>>,
 ) -> Option<Canonical<Ty>> {
     let deref_trait = match db.lang_item(krate.into(), "deref".into())? {
-        LangItemTarget::TraitId(t) => Trait::from(t),
+        LangItemTarget::TraitId(it) => it,
         _ => return None,
     };
-    let target = deref_trait.associated_type_by_name(db, &name::TARGET_TYPE)?;
+    let target = db.trait_data(deref_trait).associated_type_by_name(&name::TARGET_TYPE)?;
 
-    let generic_params = db.generic_params(target.id.into());
+    let generic_params = db.generic_params(target.into());
     if generic_params.count_params_including_parent() != 1 {
         // the Target type + Deref trait should only have one generic parameter,
         // namely Deref's Self type
@@ -69,7 +69,7 @@ fn deref_by_trait(
 
     let projection = super::traits::ProjectionPredicate {
         ty: Ty::Bound(0),
-        projection_ty: super::ProjectionTy { associated_ty: target.id, parameters },
+        projection_ty: super::ProjectionTy { associated_ty: target, parameters },
     };
 
     let obligation = super::Obligation::Projection(projection);
diff --git a/crates/ra_hir/src/ty/infer.rs b/crates/ra_hir/src/ty/infer.rs
index fce45321d..beb2efb7a 100644
--- a/crates/ra_hir/src/ty/infer.rs
+++ b/crates/ra_hir/src/ty/infer.rs
@@ -35,15 +35,15 @@ use test_utils::tested_by;
 
 use super::{
     traits::{Guidance, Obligation, ProjectionPredicate, Solution},
-    ApplicationTy, InEnvironment, ProjectionTy, Substs, TraitEnvironment, TraitRef, Ty, TypableDef,
-    TypeCtor, TypeWalk, Uncertain,
+    ApplicationTy, InEnvironment, ProjectionTy, Substs, TraitEnvironment, TraitRef, Ty, TypeCtor,
+    TypeWalk, Uncertain,
 };
 use crate::{
     code_model::TypeAlias,
     db::HirDatabase,
     expr::{BindingAnnotation, Body, ExprId, PatId},
     ty::infer::diagnostics::InferenceDiagnostic,
-    Adt, AssocItem, DefWithBody, FloatTy, Function, IntTy, Path, StructField, Trait, VariantDef,
+    AssocItem, DefWithBody, FloatTy, Function, IntTy, Path, StructField, VariantDef,
 };
 
 macro_rules! ty_app {
@@ -520,45 +520,22 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             None => return (Ty::Unknown, None),
         };
         let resolver = &self.resolver;
-        let def: TypableDef =
-            // FIXME: this should resolve assoc items as well, see this example:
-            // https://play.rust-lang.org/?gist=087992e9e22495446c01c0d4e2d69521
-            match resolver.resolve_path_in_type_ns_fully(self.db, &path) {
-                Some(TypeNs::AdtId(AdtId::StructId(it))) => it.into(),
-                Some(TypeNs::AdtId(AdtId::UnionId(it))) => it.into(),
-                Some(TypeNs::AdtSelfType(adt)) => adt.into(),
-                Some(TypeNs::EnumVariantId(it)) => it.into(),
-                Some(TypeNs::TypeAliasId(it)) => it.into(),
-
-                Some(TypeNs::SelfType(_)) |
-                Some(TypeNs::GenericParam(_)) |
-                Some(TypeNs::BuiltinType(_)) |
-                Some(TypeNs::TraitId(_)) |
-                Some(TypeNs::AdtId(AdtId::EnumId(_))) |
-                None => {
-                    return (Ty::Unknown, None)
-                }
-            };
-        // FIXME remove the duplication between here and `Ty::from_path`?
-        let substs = Ty::substs_from_path(self.db, resolver, path, def);
-        match def {
-            TypableDef::Adt(Adt::Struct(s)) => {
-                let ty = s.ty(self.db);
+        // FIXME: this should resolve assoc items as well, see this example:
+        // https://play.rust-lang.org/?gist=087992e9e22495446c01c0d4e2d69521
+        match resolver.resolve_path_in_type_ns_fully(self.db, &path) {
+            Some(TypeNs::AdtId(AdtId::StructId(strukt))) => {
+                let substs = Ty::substs_from_path(self.db, resolver, path, strukt.into());
+                let ty = self.db.ty(strukt.into());
                 let ty = self.insert_type_vars(ty.apply_substs(substs));
-                (ty, Some(s.into()))
+                (ty, Some(VariantDef::Struct(strukt.into())))
             }
-            TypableDef::EnumVariant(var) => {
-                let ty = var.parent_enum(self.db).ty(self.db);
+            Some(TypeNs::EnumVariantId(var)) => {
+                let substs = Ty::substs_from_path(self.db, resolver, path, var.into());
+                let ty = self.db.ty(var.parent.into());
                 let ty = self.insert_type_vars(ty.apply_substs(substs));
-                (ty, Some(var.into()))
+                (ty, Some(VariantDef::EnumVariant(var.into())))
             }
-            TypableDef::Adt(Adt::Enum(_))
-            | TypableDef::Adt(Adt::Union(_))
-            | TypableDef::TypeAlias(_)
-            | TypableDef::Function(_)
-            | TypableDef::Const(_)
-            | TypableDef::Static(_)
-            | TypableDef::BuiltinType(_) => (Ty::Unknown, None),
+            Some(_) | None => (Ty::Unknown, None),
         }
     }
 
@@ -582,20 +559,20 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
     fn resolve_into_iter_item(&self) -> Option<TypeAlias> {
         let path = known::std_iter_into_iterator();
-        let trait_: Trait = self.resolver.resolve_known_trait(self.db, &path)?.into();
-        trait_.associated_type_by_name(self.db, &name::ITEM_TYPE)
+        let trait_ = self.resolver.resolve_known_trait(self.db, &path)?;
+        self.db.trait_data(trait_).associated_type_by_name(&name::ITEM_TYPE).map(TypeAlias::from)
     }
 
     fn resolve_ops_try_ok(&self) -> Option<TypeAlias> {
         let path = known::std_ops_try();
-        let trait_: Trait = self.resolver.resolve_known_trait(self.db, &path)?.into();
-        trait_.associated_type_by_name(self.db, &name::OK_TYPE)
+        let trait_ = self.resolver.resolve_known_trait(self.db, &path)?;
+        self.db.trait_data(trait_).associated_type_by_name(&name::OK_TYPE).map(TypeAlias::from)
     }
 
     fn resolve_future_future_output(&self) -> Option<TypeAlias> {
         let path = known::std_future_future();
-        let trait_: Trait = self.resolver.resolve_known_trait(self.db, &path)?.into();
-        trait_.associated_type_by_name(self.db, &name::OUTPUT_TYPE)
+        let trait_ = self.resolver.resolve_known_trait(self.db, &path)?;
+        self.db.trait_data(trait_).associated_type_by_name(&name::OUTPUT_TYPE).map(TypeAlias::from)
     }
 
     fn resolve_boxed_box(&self) -> Option<AdtId> {
diff --git a/crates/ra_hir/src/ty/infer/expr.rs b/crates/ra_hir/src/ty/infer/expr.rs
index 3d0895dc6..eb221d6bc 100644
--- a/crates/ra_hir/src/ty/infer/expr.rs
+++ b/crates/ra_hir/src/ty/infer/expr.rs
@@ -17,8 +17,8 @@ use crate::{
     expr::{Array, BinaryOp, Expr, ExprId, Literal, Statement, UnaryOp},
     ty::{
         autoderef, method_resolution, op, traits::InEnvironment, CallableDef, InferTy, IntTy,
-        Mutability, Namespace, Obligation, ProjectionPredicate, ProjectionTy, Substs, TraitRef, Ty,
-        TypeCtor, TypeWalk, Uncertain,
+        Mutability, Obligation, ProjectionPredicate, ProjectionTy, Substs, TraitRef, Ty, TypeCtor,
+        TypeWalk, Uncertain,
     },
     Name,
 };
@@ -558,11 +558,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             Some((ty, func)) => {
                 let ty = canonicalized_receiver.decanonicalize_ty(ty);
                 self.write_method_resolution(tgt_expr, func);
-                (
-                    ty,
-                    self.db.type_for_def(func.into(), Namespace::Values),
-                    Some(self.db.generic_params(func.id.into())),
-                )
+                (ty, self.db.value_ty(func.id.into()), Some(self.db.generic_params(func.id.into())))
             }
             None => (receiver_ty, Ty::Unknown, None),
         };
diff --git a/crates/ra_hir/src/ty/infer/path.rs b/crates/ra_hir/src/ty/infer/path.rs
index 6165eba4f..be2067dd4 100644
--- a/crates/ra_hir/src/ty/infer/path.rs
+++ b/crates/ra_hir/src/ty/infer/path.rs
@@ -7,7 +7,7 @@ use hir_def::{
 
 use crate::{
     db::HirDatabase,
-    ty::{method_resolution, Namespace, Substs, Ty, TypableDef, TypeWalk},
+    ty::{method_resolution, Substs, Ty, TypeWalk, ValueTyDefId},
     AssocItem, Container, Function, Name, Path,
 };
 
@@ -56,7 +56,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             }
         };
 
-        let typable: TypableDef = match value {
+        let typable: ValueTyDefId = match value {
             ValueNs::LocalBinding(pat) => {
                 let ty = self.result.type_of_pat.get(pat)?.clone();
                 let ty = self.resolve_ty_as_possible(&mut vec![], ty);
@@ -69,11 +69,10 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             ValueNs::EnumVariantId(it) => it.into(),
         };
 
-        let mut ty = self.db.type_for_def(typable, Namespace::Values);
+        let mut ty = self.db.value_ty(typable);
         if let Some(self_subst) = self_subst {
             ty = ty.subst(&self_subst);
         }
-
         let substs = Ty::substs_from_path(self.db, &self.resolver, path, typable);
         let ty = ty.subst(&substs);
         Some(ty)
@@ -143,24 +142,27 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         id: ExprOrPatId,
     ) -> Option<(ValueNs, Option<Substs>)> {
         let trait_ = trait_ref.trait_;
-        let item = trait_.items(self.db).iter().copied().find_map(|item| match item {
-            AssocItem::Function(func) => {
-                if segment.name == func.name(self.db) {
-                    Some(AssocItem::Function(func))
-                } else {
-                    None
-                }
-            }
+        let item =
+            self.db.trait_data(trait_).items.iter().map(|(_name, id)| (*id).into()).find_map(
+                |item| match item {
+                    AssocItem::Function(func) => {
+                        if segment.name == func.name(self.db) {
+                            Some(AssocItem::Function(func))
+                        } else {
+                            None
+                        }
+                    }
 
-            AssocItem::Const(konst) => {
-                if konst.name(self.db).map_or(false, |n| n == segment.name) {
-                    Some(AssocItem::Const(konst))
-                } else {
-                    None
-                }
-            }
-            AssocItem::TypeAlias(_) => None,
-        })?;
+                    AssocItem::Const(konst) => {
+                        if konst.name(self.db).map_or(false, |n| n == segment.name) {
+                            Some(AssocItem::Const(konst))
+                        } else {
+                            None
+                        }
+                    }
+                    AssocItem::TypeAlias(_) => None,
+                },
+            )?;
         let def = match item {
             AssocItem::Function(f) => ValueNs::FunctionId(f.id),
             AssocItem::Const(c) => ValueNs::ConstId(c.id),
@@ -212,7 +214,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                             .fill_with_params()
                             .build();
                         self.obligations.push(super::Obligation::Trait(TraitRef {
-                            trait_: t,
+                            trait_: t.id,
                             substs: trait_substs,
                         }));
                         Some(substs)
diff --git a/crates/ra_hir/src/ty/lower.rs b/crates/ra_hir/src/ty/lower.rs
index 2d23890a5..709492d21 100644
--- a/crates/ra_hir/src/ty/lower.rs
+++ b/crates/ra_hir/src/ty/lower.rs
@@ -14,8 +14,8 @@ use hir_def::{
     path::{GenericArg, PathSegment},
     resolver::{HasResolver, Resolver, TypeNs},
     type_ref::{TypeBound, TypeRef},
-    AdtId, AstItemDef, EnumVariantId, FunctionId, GenericDefId, HasModule, LocalStructFieldId,
-    Lookup, StructId, VariantId,
+    AdtId, AstItemDef, ConstId, EnumId, EnumVariantId, FunctionId, GenericDefId, HasModule,
+    LocalStructFieldId, Lookup, StaticId, StructId, TraitId, TypeAliasId, UnionId, VariantId,
 };
 use ra_arena::map::ArenaMap;
 use ra_db::CrateId;
@@ -28,24 +28,13 @@ use crate::{
     db::HirDatabase,
     ty::{
         primitive::{FloatTy, IntTy},
-        Adt,
+        utils::{all_super_traits, associated_type_by_name_including_super_traits},
     },
     util::make_mut_slice,
-    Const, Enum, EnumVariant, Function, ImplBlock, ModuleDef, Path, Static, Struct, Trait,
+    Adt, Const, Enum, EnumVariant, Function, ImplBlock, ModuleDef, Path, Static, Struct, Trait,
     TypeAlias, Union,
 };
 
-// FIXME: this is only really used in `type_for_def`, which contains a bunch of
-// impossible cases. Perhaps we should recombine `TypeableDef` and `Namespace`
-// into a `AsTypeDef`, `AsValueDef` enums?
-#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub enum Namespace {
-    Types,
-    Values,
-    // Note that only type inference uses this enum, and it doesn't care about macros.
-    // Macro,
-}
-
 impl Ty {
     pub(crate) fn from_hir(db: &impl HirDatabase, resolver: &Resolver, type_ref: &TypeRef) -> Self {
         match type_ref {
@@ -169,14 +158,16 @@ impl Ty {
                 );
                 return if remaining_segments.len() == 1 {
                     let segment = &remaining_segments[0];
-                    match trait_ref
-                        .trait_
-                        .associated_type_by_name_including_super_traits(db, &segment.name)
-                    {
+                    let associated_ty = associated_type_by_name_including_super_traits(
+                        db,
+                        trait_ref.trait_,
+                        &segment.name,
+                    );
+                    match associated_ty {
                         Some(associated_ty) => {
                             // FIXME handle type parameters on the segment
                             Ty::Projection(ProjectionTy {
-                                associated_ty: associated_ty.id,
+                                associated_ty,
                                 parameters: trait_ref.substs,
                             })
                         }
@@ -260,18 +251,16 @@ impl Ty {
             GenericPredicate::Implemented(tr) if tr.self_ty() == &self_ty => Some(tr.trait_),
             _ => None,
         });
-        let traits = traits_from_env.flat_map(|t| t.all_super_traits(db));
+        let traits = traits_from_env.flat_map(|t| all_super_traits(db, t)).map(Trait::from);
         for t in traits {
-            if let Some(associated_ty) = t.associated_type_by_name(db, &segment.name) {
+            if let Some(associated_ty) = db.trait_data(t.id).associated_type_by_name(&segment.name)
+            {
                 let substs = Substs::build_for_def(db, t.id)
                     .push(self_ty.clone())
                     .fill_with_unknown()
                     .build();
                 // FIXME handle type parameters on the segment
-                return Ty::Projection(ProjectionTy {
-                    associated_ty: associated_ty.id,
-                    parameters: substs,
-                });
+                return Ty::Projection(ProjectionTy { associated_ty, parameters: substs });
             }
         }
         Ty::Unknown
@@ -281,27 +270,15 @@ impl Ty {
         db: &impl HirDatabase,
         resolver: &Resolver,
         segment: &PathSegment,
-        typable: TypableDef,
+        typable: TyDefId,
     ) -> Ty {
-        let ty = db.type_for_def(typable, Namespace::Types);
-        let substs = Ty::substs_from_path_segment(db, resolver, segment, typable);
-        ty.subst(&substs)
-    }
-
-    pub(super) fn substs_from_path_segment(
-        db: &impl HirDatabase,
-        resolver: &Resolver,
-        segment: &PathSegment,
-        resolved: TypableDef,
-    ) -> Substs {
-        let def_generic: Option<GenericDefId> = match resolved {
-            TypableDef::Function(func) => Some(func.id.into()),
-            TypableDef::Adt(adt) => Some(adt.into()),
-            TypableDef::EnumVariant(var) => Some(var.parent_enum(db).id.into()),
-            TypableDef::TypeAlias(t) => Some(t.id.into()),
-            TypableDef::Const(_) | TypableDef::Static(_) | TypableDef::BuiltinType(_) => None,
+        let generic_def = match typable {
+            TyDefId::BuiltinType(_) => None,
+            TyDefId::AdtId(it) => Some(it.into()),
+            TyDefId::TypeAliasId(it) => Some(it.into()),
         };
-        substs_from_path_segment(db, resolver, segment, def_generic, false)
+        let substs = substs_from_path_segment(db, resolver, segment, generic_def, false);
+        db.ty(typable).subst(&substs)
     }
 
     /// Collect generic arguments from a path into a `Substs`. See also
@@ -310,17 +287,18 @@ impl Ty {
         db: &impl HirDatabase,
         resolver: &Resolver,
         path: &Path,
-        resolved: TypableDef,
+        // Note that we don't call `db.value_type(resolved)` here,
+        // `ValueTyDefId` is just a convenient way to pass generics and
+        // special-case enum variants
+        resolved: ValueTyDefId,
     ) -> Substs {
         let last = path.segments.last().expect("path should have at least one segment");
-        let segment = match resolved {
-            TypableDef::Function(_)
-            | TypableDef::Adt(_)
-            | TypableDef::Const(_)
-            | TypableDef::Static(_)
-            | TypableDef::TypeAlias(_)
-            | TypableDef::BuiltinType(_) => last,
-            TypableDef::EnumVariant(_) => {
+        let (segment, generic_def) = match resolved {
+            ValueTyDefId::FunctionId(it) => (last, Some(it.into())),
+            ValueTyDefId::StructId(it) => (last, Some(it.into())),
+            ValueTyDefId::ConstId(it) => (last, Some(it.into())),
+            ValueTyDefId::StaticId(_) => (last, None),
+            ValueTyDefId::EnumVariantId(var) => {
                 // the generic args for an enum variant may be either specified
                 // on the segment referring to the enum, or on the segment
                 // referring to the variant. So `Option::<T>::None` and
@@ -334,10 +312,10 @@ impl Ty {
                     // Option::None::<T>
                     last
                 };
-                segment
+                (segment, Some(var.parent.into()))
             }
         };
-        Ty::substs_from_path_segment(db, resolver, segment, resolved)
+        substs_from_path_segment(db, resolver, segment, generic_def, false)
     }
 }
 
@@ -422,7 +400,7 @@ impl TraitRef {
         if let Some(self_ty) = explicit_self_ty {
             make_mut_slice(&mut substs.0)[0] = self_ty;
         }
-        TraitRef { trait_: resolved, substs }
+        TraitRef { trait_: resolved.id, substs }
     }
 
     pub(crate) fn from_hir(
@@ -449,8 +427,8 @@ impl TraitRef {
         substs_from_path_segment(db, resolver, segment, Some(resolved.id.into()), !has_self_param)
     }
 
-    pub(crate) fn for_trait(db: &impl HirDatabase, trait_: Trait) -> TraitRef {
-        let substs = Substs::identity(&db.generic_params(trait_.id.into()));
+    pub(crate) fn for_trait(db: &impl HirDatabase, trait_: TraitId) -> TraitRef {
+        let substs = Substs::identity(&db.generic_params(trait_.into()));
         TraitRef { trait_, substs }
     }
 
@@ -509,10 +487,11 @@ fn assoc_type_bindings_from_type_bound<'a>(
         .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
         .map(move |(name, type_ref)| {
             let associated_ty =
-                match trait_ref.trait_.associated_type_by_name_including_super_traits(db, &name) {
-                    None => return GenericPredicate::Error,
-                    Some(t) => t.id,
-                };
+                associated_type_by_name_including_super_traits(db, trait_ref.trait_, &name);
+            let associated_ty = match associated_ty {
+                None => return GenericPredicate::Error,
+                Some(t) => t,
+            };
             let projection_ty =
                 ProjectionTy { associated_ty, parameters: trait_ref.substs.clone() };
             let ty = Ty::from_hir(db, resolver, type_ref);
@@ -521,33 +500,6 @@ fn assoc_type_bindings_from_type_bound<'a>(
         })
 }
 
-/// Build the declared type of an item. This depends on the namespace; e.g. for
-/// `struct Foo(usize)`, we have two types: The type of the struct itself, and
-/// the constructor function `(usize) -> Foo` which lives in the values
-/// namespace.
-pub(crate) fn type_for_def(db: &impl HirDatabase, def: TypableDef, ns: Namespace) -> Ty {
-    match (def, ns) {
-        (TypableDef::Function(f), Namespace::Values) => type_for_fn(db, f),
-        (TypableDef::Adt(Adt::Struct(s)), Namespace::Values) => type_for_struct_constructor(db, s),
-        (TypableDef::Adt(adt), Namespace::Types) => type_for_adt(db, adt),
-        (TypableDef::EnumVariant(v), Namespace::Values) => type_for_enum_variant_constructor(db, v),
-        (TypableDef::TypeAlias(t), Namespace::Types) => type_for_type_alias(db, t),
-        (TypableDef::Const(c), Namespace::Values) => type_for_const(db, c),
-        (TypableDef::Static(c), Namespace::Values) => type_for_static(db, c),
-        (TypableDef::BuiltinType(t), Namespace::Types) => type_for_builtin(t),
-
-        // 'error' cases:
-        (TypableDef::Function(_), Namespace::Types) => Ty::Unknown,
-        (TypableDef::Adt(Adt::Union(_)), Namespace::Values) => Ty::Unknown,
-        (TypableDef::Adt(Adt::Enum(_)), Namespace::Values) => Ty::Unknown,
-        (TypableDef::EnumVariant(_), Namespace::Types) => Ty::Unknown,
-        (TypableDef::TypeAlias(_), Namespace::Values) => Ty::Unknown,
-        (TypableDef::Const(_), Namespace::Types) => Ty::Unknown,
-        (TypableDef::Static(_), Namespace::Types) => Ty::Unknown,
-        (TypableDef::BuiltinType(_), Namespace::Values) => Ty::Unknown,
-    }
-}
-
 /// Build the signature of a callable item (function, struct or enum variant).
 pub(crate) fn callable_item_sig(db: &impl HirDatabase, def: CallableDef) -> FnSig {
     match def {
@@ -646,24 +598,24 @@ fn fn_sig_for_fn(db: &impl HirDatabase, def: FunctionId) -> FnSig {
 
 /// Build the declared type of a function. This should not need to look at the
 /// function body.
-fn type_for_fn(db: &impl HirDatabase, def: Function) -> Ty {
-    let generics = db.generic_params(def.id.into());
+fn type_for_fn(db: &impl HirDatabase, def: FunctionId) -> Ty {
+    let generics = db.generic_params(def.into());
     let substs = Substs::identity(&generics);
-    Ty::apply(TypeCtor::FnDef(def.id.into()), substs)
+    Ty::apply(TypeCtor::FnDef(def.into()), substs)
 }
 
 /// Build the declared type of a const.
-fn type_for_const(db: &impl HirDatabase, def: Const) -> Ty {
-    let data = db.const_data(def.id);
-    let resolver = def.id.resolver(db);
+fn type_for_const(db: &impl HirDatabase, def: ConstId) -> Ty {
+    let data = db.const_data(def);
+    let resolver = def.resolver(db);
 
     Ty::from_hir(db, &resolver, &data.type_ref)
 }
 
 /// Build the declared type of a static.
-fn type_for_static(db: &impl HirDatabase, def: Static) -> Ty {
-    let data = db.static_data(def.id);
-    let resolver = def.id.resolver(db);
+fn type_for_static(db: &impl HirDatabase, def: StaticId) -> Ty {
+    let data = db.static_data(def);
+    let resolver = def.resolver(db);
 
     Ty::from_hir(db, &resolver, &data.type_ref)
 }
@@ -687,19 +639,19 @@ fn fn_sig_for_struct_constructor(db: &impl HirDatabase, def: StructId) -> FnSig
         .iter()
         .map(|(_, field)| Ty::from_hir(db, &resolver, &field.type_ref))
         .collect::<Vec<_>>();
-    let ret = type_for_adt(db, Struct::from(def));
+    let ret = type_for_adt(db, def.into());
     FnSig::from_params_and_return(params, ret)
 }
 
 /// Build the type of a tuple struct constructor.
-fn type_for_struct_constructor(db: &impl HirDatabase, def: Struct) -> Ty {
-    let struct_data = db.struct_data(def.id.into());
+fn type_for_struct_constructor(db: &impl HirDatabase, def: StructId) -> Ty {
+    let struct_data = db.struct_data(def.into());
     if struct_data.variant_data.is_unit() {
-        return type_for_adt(db, def); // Unit struct
+        return type_for_adt(db, def.into()); // Unit struct
     }
-    let generics = db.generic_params(def.id.into());
+    let generics = db.generic_params(def.into());
     let substs = Substs::identity(&generics);
-    Ty::apply(TypeCtor::FnDef(def.id.into()), substs)
+    Ty::apply(TypeCtor::FnDef(def.into()), substs)
 }
 
 fn fn_sig_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariantId) -> FnSig {
@@ -713,34 +665,33 @@ fn fn_sig_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariantId
         .collect::<Vec<_>>();
     let generics = db.generic_params(def.parent.into());
     let substs = Substs::identity(&generics);
-    let ret = type_for_adt(db, Enum::from(def.parent)).subst(&substs);
+    let ret = type_for_adt(db, def.parent.into()).subst(&substs);
     FnSig::from_params_and_return(params, ret)
 }
 
 /// Build the type of a tuple enum variant constructor.
-fn type_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariant) -> Ty {
-    let var_data = def.variant_data(db);
+fn type_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariantId) -> Ty {
+    let enum_data = db.enum_data(def.parent);
+    let var_data = &enum_data.variants[def.local_id].variant_data;
     if var_data.is_unit() {
-        return type_for_adt(db, def.parent_enum(db)); // Unit variant
+        return type_for_adt(db, def.parent.into()); // Unit variant
     }
-    let generics = db.generic_params(def.parent_enum(db).id.into());
+    let generics = db.generic_params(def.parent.into());
     let substs = Substs::identity(&generics);
     Ty::apply(TypeCtor::FnDef(EnumVariantId::from(def).into()), substs)
 }
 
-fn type_for_adt(db: &impl HirDatabase, adt: impl Into<Adt>) -> Ty {
-    let adt = adt.into();
-    let adt_id: AdtId = adt.into();
-    let generics = db.generic_params(adt_id.into());
-    Ty::apply(TypeCtor::Adt(adt_id), Substs::identity(&generics))
+fn type_for_adt(db: &impl HirDatabase, adt: AdtId) -> Ty {
+    let generics = db.generic_params(adt.into());
+    Ty::apply(TypeCtor::Adt(adt), Substs::identity(&generics))
 }
 
-fn type_for_type_alias(db: &impl HirDatabase, t: TypeAlias) -> Ty {
-    let generics = db.generic_params(t.id.into());
-    let resolver = t.id.resolver(db);
-    let type_ref = t.type_ref(db);
+fn type_for_type_alias(db: &impl HirDatabase, t: TypeAliasId) -> Ty {
+    let generics = db.generic_params(t.into());
+    let resolver = t.resolver(db);
+    let type_ref = &db.type_alias_data(t).type_ref;
     let substs = Substs::identity(&generics);
-    let inner = Ty::from_hir(db, &resolver, &type_ref.unwrap_or(TypeRef::Error));
+    let inner = Ty::from_hir(db, &resolver, type_ref.as_ref().unwrap_or(&TypeRef::Error));
     inner.subst(&substs)
 }
 
@@ -807,3 +758,42 @@ impl From<CallableDef> for GenericDefId {
         }
     }
 }
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum TyDefId {
+    BuiltinType(BuiltinType),
+    AdtId(AdtId),
+    TypeAliasId(TypeAliasId),
+}
+impl_froms!(TyDefId: BuiltinType, AdtId(StructId, EnumId, UnionId), TypeAliasId);
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum ValueTyDefId {
+    FunctionId(FunctionId),
+    StructId(StructId),
+    EnumVariantId(EnumVariantId),
+    ConstId(ConstId),
+    StaticId(StaticId),
+}
+impl_froms!(ValueTyDefId: FunctionId, StructId, EnumVariantId, ConstId, StaticId);
+
+/// Build the declared type of an item. This depends on the namespace; e.g. for
+/// `struct Foo(usize)`, we have two types: The type of the struct itself, and
+/// the constructor function `(usize) -> Foo` which lives in the values
+/// namespace.
+pub(crate) fn ty_query(db: &impl HirDatabase, def: TyDefId) -> Ty {
+    match def {
+        TyDefId::BuiltinType(it) => type_for_builtin(it),
+        TyDefId::AdtId(it) => type_for_adt(db, it),
+        TyDefId::TypeAliasId(it) => type_for_type_alias(db, it),
+    }
+}
+pub(crate) fn value_ty_query(db: &impl HirDatabase, def: ValueTyDefId) -> Ty {
+    match def {
+        ValueTyDefId::FunctionId(it) => type_for_fn(db, it),
+        ValueTyDefId::StructId(it) => type_for_struct_constructor(db, it),
+        ValueTyDefId::EnumVariantId(it) => type_for_enum_variant_constructor(db, it),
+        ValueTyDefId::ConstId(it) => type_for_const(db, it),
+        ValueTyDefId::StaticId(it) => type_for_static(db, it),
+    }
+}
diff --git a/crates/ra_hir/src/ty/method_resolution.rs b/crates/ra_hir/src/ty/method_resolution.rs
index 489fcd64b..f1bc638ee 100644
--- a/crates/ra_hir/src/ty/method_resolution.rs
+++ b/crates/ra_hir/src/ty/method_resolution.rs
@@ -16,7 +16,7 @@ use rustc_hash::FxHashMap;
 use crate::{
     db::HirDatabase,
     ty::primitive::{FloatBitness, Uncertain},
-    ty::{Ty, TypeCtor},
+    ty::{utils::all_super_traits, Ty, TypeCtor},
     AssocItem, Crate, Function, Mutability, Name, Trait,
 };
 
@@ -68,7 +68,7 @@ impl CrateImplBlocks {
                         if let Some(tr) =
                             TraitRef::from_hir(db, &resolver, &trait_ref, Some(target_ty))
                         {
-                            res.impls_by_trait.entry(tr.trait_.id).or_default().push(impl_id);
+                            res.impls_by_trait.entry(tr.trait_).or_default().push(impl_id);
                         }
                     }
                     None => {
@@ -249,19 +249,18 @@ fn iterate_trait_method_candidates<T>(
     let traits_from_env = env
         .trait_predicates_for_self_ty(&ty.value)
         .map(|tr| tr.trait_)
-        .flat_map(|t| t.all_super_traits(db));
-    let traits = inherent_trait
-        .chain(traits_from_env)
-        .chain(resolver.traits_in_scope(db).into_iter().map(Trait::from));
+        .flat_map(|t| all_super_traits(db, t));
+    let traits =
+        inherent_trait.chain(traits_from_env).chain(resolver.traits_in_scope(db).into_iter());
     'traits: for t in traits {
-        let data = db.trait_data(t.id);
+        let data = db.trait_data(t);
 
         // we'll be lazy about checking whether the type implements the
         // trait, but if we find out it doesn't, we'll skip the rest of the
         // iteration
         let mut known_implemented = false;
-        for &item in data.items.iter() {
-            if !is_valid_candidate(db, name, mode, item.into()) {
+        for (_name, item) in data.items.iter() {
+            if !is_valid_candidate(db, name, mode, (*item).into()) {
                 continue;
             }
             if !known_implemented {
@@ -271,7 +270,7 @@ fn iterate_trait_method_candidates<T>(
                 }
             }
             known_implemented = true;
-            if let Some(result) = callback(&ty.value, item.into()) {
+            if let Some(result) = callback(&ty.value, (*item).into()) {
                 return Some(result);
             }
         }
@@ -329,7 +328,7 @@ pub(crate) fn implements_trait(
     db: &impl HirDatabase,
     resolver: &Resolver,
     krate: Crate,
-    trait_: Trait,
+    trait_: TraitId,
 ) -> bool {
     if ty.value.inherent_trait() == Some(trait_) {
         // FIXME this is a bit of a hack, since Chalk should say the same thing
@@ -372,11 +371,11 @@ impl Ty {
 fn generic_implements_goal(
     db: &impl HirDatabase,
     env: Arc<TraitEnvironment>,
-    trait_: Trait,
+    trait_: TraitId,
     self_ty: Canonical<Ty>,
 ) -> Canonical<InEnvironment<super::Obligation>> {
     let num_vars = self_ty.num_vars;
-    let substs = super::Substs::build_for_def(db, trait_.id)
+    let substs = super::Substs::build_for_def(db, trait_)
         .push(self_ty.value)
         .fill_with_bound_vars(num_vars as u32)
         .build();
diff --git a/crates/ra_hir/src/ty/traits.rs b/crates/ra_hir/src/ty/traits.rs
index 2eeb03099..a91c2476b 100644
--- a/crates/ra_hir/src/ty/traits.rs
+++ b/crates/ra_hir/src/ty/traits.rs
@@ -2,14 +2,15 @@
 use std::sync::{Arc, Mutex};
 
 use chalk_ir::{cast::Cast, family::ChalkIr};
-use hir_def::DefWithBodyId;
+use hir_def::{expr::ExprId, DefWithBodyId};
 use log::debug;
 use ra_db::{impl_intern_key, salsa};
 use ra_prof::profile;
 use rustc_hash::FxHashSet;
 
+use crate::{db::HirDatabase, Crate, ImplBlock, Trait, TypeAlias};
+
 use super::{Canonical, GenericPredicate, HirDisplay, ProjectionTy, TraitRef, Ty, TypeWalk};
-use crate::{db::HirDatabase, expr::ExprId, Crate, ImplBlock, Trait, TypeAlias};
 
 use self::chalk::{from_chalk, ToChalk};
 
diff --git a/crates/ra_hir/src/ty/traits/chalk.rs b/crates/ra_hir/src/ty/traits/chalk.rs
index 06388a3ce..4b0f4f56c 100644
--- a/crates/ra_hir/src/ty/traits/chalk.rs
+++ b/crates/ra_hir/src/ty/traits/chalk.rs
@@ -9,7 +9,9 @@ use chalk_ir::{
 };
 use chalk_rust_ir::{AssociatedTyDatum, AssociatedTyValue, ImplDatum, StructDatum, TraitDatum};
 
-use hir_def::{lang_item::LangItemTarget, ContainerId, GenericDefId, Lookup, TypeAliasId};
+use hir_def::{
+    lang_item::LangItemTarget, AstItemDef, ContainerId, GenericDefId, Lookup, TraitId, TypeAliasId,
+};
 use hir_expand::name;
 
 use ra_db::salsa::{InternId, InternKey};
@@ -19,7 +21,7 @@ use crate::{
     db::HirDatabase,
     ty::display::HirDisplay,
     ty::{ApplicationTy, GenericPredicate, ProjectionTy, Substs, TraitRef, Ty, TypeCtor, TypeWalk},
-    Crate, ImplBlock, Trait, TypeAlias,
+    Crate, ImplBlock, TypeAlias,
 };
 
 /// This represents a trait whose name we could not resolve.
@@ -167,15 +169,15 @@ impl ToChalk for TraitRef {
     }
 }
 
-impl ToChalk for Trait {
+impl ToChalk for TraitId {
     type Chalk = chalk_ir::TraitId;
 
     fn to_chalk(self, _db: &impl HirDatabase) -> chalk_ir::TraitId {
-        chalk_ir::TraitId(id_to_chalk(self.id))
+        chalk_ir::TraitId(id_to_chalk(self))
     }
 
-    fn from_chalk(_db: &impl HirDatabase, trait_id: chalk_ir::TraitId) -> Trait {
-        Trait { id: id_from_chalk(trait_id.0) }
+    fn from_chalk(_db: &impl HirDatabase, trait_id: chalk_ir::TraitId) -> TraitId {
+        id_from_chalk(trait_id.0)
     }
 }
 
@@ -443,10 +445,10 @@ where
         if trait_id == UNKNOWN_TRAIT {
             return Vec::new();
         }
-        let trait_: Trait = from_chalk(self.db, trait_id);
+        let trait_: TraitId = from_chalk(self.db, trait_id);
         let mut result: Vec<_> = self
             .db
-            .impls_for_trait(self.krate, trait_)
+            .impls_for_trait(self.krate, trait_.into())
             .iter()
             .copied()
             .map(Impl::ImplBlock)
@@ -516,7 +518,7 @@ pub(crate) fn associated_ty_data_query(
         where_clauses: vec![],
     };
     let datum = AssociatedTyDatum {
-        trait_id: Trait::from(trait_).to_chalk(db),
+        trait_id: trait_.to_chalk(db),
         id,
         name: lalrpop_intern::intern(&db.type_alias_data(type_alias).name.to_string()),
         binders: make_binders(bound_data, generic_params.count_params_including_parent()),
@@ -548,29 +550,23 @@ pub(crate) fn trait_datum_query(
             associated_ty_ids: vec![],
         });
     }
-    let trait_: Trait = from_chalk(db, trait_id);
-    debug!("trait {:?} = {:?}", trait_id, trait_.name(db));
-    let generic_params = db.generic_params(trait_.id.into());
+    let trait_: TraitId = from_chalk(db, trait_id);
+    let trait_data = db.trait_data(trait_);
+    debug!("trait {:?} = {:?}", trait_id, trait_data.name);
+    let generic_params = db.generic_params(trait_.into());
     let bound_vars = Substs::bound_vars(&generic_params);
     let flags = chalk_rust_ir::TraitFlags {
-        auto: trait_.is_auto(db),
-        upstream: trait_.module(db).krate() != krate,
+        auto: trait_data.auto,
+        upstream: trait_.module(db).krate != krate.crate_id,
         non_enumerable: true,
         coinductive: false, // only relevant for Chalk testing
         // FIXME set these flags correctly
         marker: false,
         fundamental: false,
     };
-    let where_clauses = convert_where_clauses(db, trait_.id.into(), &bound_vars);
-    let associated_ty_ids = trait_
-        .items(db)
-        .into_iter()
-        .filter_map(|trait_item| match trait_item {
-            crate::AssocItem::TypeAlias(type_alias) => Some(type_alias.id),
-            _ => None,
-        })
-        .map(|type_alias| type_alias.to_chalk(db))
-        .collect();
+    let where_clauses = convert_where_clauses(db, trait_.into(), &bound_vars);
+    let associated_ty_ids =
+        trait_data.associated_types().map(|type_alias| type_alias.to_chalk(db)).collect();
     let trait_datum_bound = chalk_rust_ir::TraitDatumBound { where_clauses };
     let trait_datum = TraitDatum {
         id: trait_id,
@@ -661,6 +657,7 @@ fn impl_block_datum(
     };
 
     let impl_datum_bound = chalk_rust_ir::ImplDatumBound { trait_ref, where_clauses };
+    let trait_data = db.trait_data(trait_);
     let associated_ty_value_ids = impl_block
         .items(db)
         .into_iter()
@@ -670,7 +667,7 @@ fn impl_block_datum(
         })
         .filter(|type_alias| {
             // don't include associated types that don't exist in the trait
-            trait_.associated_type_by_name(db, &type_alias.name(db)).is_some()
+            trait_data.associated_type_by_name(&type_alias.name(db)).is_some()
         })
         .map(|type_alias| AssocTyValue::TypeAlias(type_alias).to_chalk(db))
         .collect();
@@ -713,7 +710,7 @@ fn closure_fn_trait_impl_datum(
     // and don't want to return a valid value only to find out later that FnOnce
     // is broken
     let fn_once_trait = get_fn_trait(db, krate, super::FnTrait::FnOnce)?;
-    fn_once_trait.associated_type_by_name(db, &name::OUTPUT_TYPE)?;
+    let _output = db.trait_data(fn_once_trait).associated_type_by_name(&name::OUTPUT_TYPE)?;
 
     let num_args: u16 = match &db.body(data.def.into())[data.expr] {
         crate::expr::Expr::Lambda { args, .. } => args.len() as u16,
@@ -735,8 +732,8 @@ fn closure_fn_trait_impl_datum(
     let self_ty = Ty::apply_one(TypeCtor::Closure { def: data.def, expr: data.expr }, sig_ty);
 
     let trait_ref = TraitRef {
-        trait_,
-        substs: Substs::build_for_def(db, trait_.id).push(self_ty).push(arg_ty).build(),
+        trait_: trait_.into(),
+        substs: Substs::build_for_def(db, trait_).push(self_ty).push(arg_ty).build(),
     };
 
     let output_ty_id = AssocTyValue::ClosureFnTraitImplOutput(data.clone()).to_chalk(db);
@@ -783,13 +780,13 @@ fn type_alias_associated_ty_value(
         .target_trait_ref(db)
         .expect("assoc ty value should not exist") // we don't return any assoc ty values if the impl'd trait can't be resolved
         .trait_;
-    let assoc_ty = trait_
-        .associated_type_by_name(db, &type_alias.name(db))
-        .expect("assoc ty value should not exist") // validated when building the impl data as well
-        .id;
+    let assoc_ty = db
+        .trait_data(trait_)
+        .associated_type_by_name(&type_alias.name(db))
+        .expect("assoc ty value should not exist"); // validated when building the impl data as well
     let generic_params = db.generic_params(impl_block.id.into());
     let bound_vars = Substs::bound_vars(&generic_params);
-    let ty = db.type_for_def(type_alias.into(), crate::ty::Namespace::Types).subst(&bound_vars);
+    let ty = db.ty(type_alias.id.into()).subst(&bound_vars);
     let value_bound = chalk_rust_ir::AssociatedTyValueBound { ty: ty.to_chalk(db) };
     let value = chalk_rust_ir::AssociatedTyValue {
         impl_id,
@@ -819,10 +816,10 @@ fn closure_fn_trait_output_assoc_ty_value(
     let fn_once_trait =
         get_fn_trait(db, krate, super::FnTrait::FnOnce).expect("assoc ty value should not exist");
 
-    let output_ty_id = fn_once_trait
-        .associated_type_by_name(db, &name::OUTPUT_TYPE)
-        .expect("assoc ty value should not exist")
-        .id;
+    let output_ty_id = db
+        .trait_data(fn_once_trait)
+        .associated_type_by_name(&name::OUTPUT_TYPE)
+        .expect("assoc ty value should not exist");
 
     let value_bound = chalk_rust_ir::AssociatedTyValueBound { ty: output_ty.to_chalk(db) };
 
@@ -834,10 +831,10 @@ fn closure_fn_trait_output_assoc_ty_value(
     Arc::new(value)
 }
 
-fn get_fn_trait(db: &impl HirDatabase, krate: Crate, fn_trait: super::FnTrait) -> Option<Trait> {
+fn get_fn_trait(db: &impl HirDatabase, krate: Crate, fn_trait: super::FnTrait) -> Option<TraitId> {
     let target = db.lang_item(krate.crate_id, fn_trait.lang_item_name().into())?;
     match target {
-        LangItemTarget::TraitId(t) => Some(t.into()),
+        LangItemTarget::TraitId(t) => Some(t),
         _ => None,
     }
 }
diff --git a/crates/ra_hir/src/ty/utils.rs b/crates/ra_hir/src/ty/utils.rs
new file mode 100644
index 000000000..80ffceb4b
--- /dev/null
+++ b/crates/ra_hir/src/ty/utils.rs
@@ -0,0 +1,63 @@
+//! Helper functions for working with def, which don't need to be a separate
+//! query, but can't be computed directly from `*Data` (ie, which need a `db`).
+
+use hir_def::{
+    db::DefDatabase,
+    resolver::{HasResolver, TypeNs},
+    type_ref::TypeRef,
+    TraitId, TypeAliasId,
+};
+use hir_expand::name::{self, Name};
+
+// FIXME: this is wrong, b/c it can't express `trait T: PartialEq<()>`.
+// We should return a `TraitREf` here.
+fn direct_super_traits(db: &impl DefDatabase, trait_: TraitId) -> Vec<TraitId> {
+    let resolver = trait_.resolver(db);
+    // returning the iterator directly doesn't easily work because of
+    // lifetime problems, but since there usually shouldn't be more than a
+    // few direct traits this should be fine (we could even use some kind of
+    // SmallVec if performance is a concern)
+    db.generic_params(trait_.into())
+        .where_predicates
+        .iter()
+        .filter_map(|pred| match &pred.type_ref {
+            TypeRef::Path(p) if p.as_ident() == Some(&name::SELF_TYPE) => pred.bound.as_path(),
+            _ => None,
+        })
+        .filter_map(|path| match resolver.resolve_path_in_type_ns_fully(db, path) {
+            Some(TypeNs::TraitId(t)) => Some(t),
+            _ => None,
+        })
+        .collect()
+}
+
+/// Returns an iterator over the whole super trait hierarchy (including the
+/// trait itself).
+pub(super) fn all_super_traits(db: &impl DefDatabase, trait_: TraitId) -> Vec<TraitId> {
+    // we need to take care a bit here to avoid infinite loops in case of cycles
+    // (i.e. if we have `trait A: B; trait B: A;`)
+    let mut result = vec![trait_];
+    let mut i = 0;
+    while i < result.len() {
+        let t = result[i];
+        // yeah this is quadratic, but trait hierarchies should be flat
+        // enough that this doesn't matter
+        for tt in direct_super_traits(db, t) {
+            if !result.contains(&tt) {
+                result.push(tt);
+            }
+        }
+        i += 1;
+    }
+    result
+}
+
+pub(super) fn associated_type_by_name_including_super_traits(
+    db: &impl DefDatabase,
+    trait_: TraitId,
+    name: &Name,
+) -> Option<TypeAliasId> {
+    all_super_traits(db, trait_)
+        .into_iter()
+        .find_map(|t| db.trait_data(t).associated_type_by_name(name))
+}