10 files changed, 188 insertions, 108 deletions

diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index a132d128b..550ab1a98 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -12,8 +12,8 @@ use hir_def::{
     builtin_type::BuiltinType,
     traits::TraitData,
     type_ref::{Mutability, TypeRef},
-    AssocItemId, ContainerId, CrateModuleId, HasModule, ImplId, LocalEnumVariantId,
-    LocalStructFieldId, Lookup, ModuleId, UnionId,
+    ContainerId, CrateModuleId, HasModule, ImplId, LocalEnumVariantId, LocalStructFieldId, Lookup,
+    ModuleId, UnionId,
 };
 use hir_expand::{
     diagnostics::DiagnosticSink,
@@ -842,9 +842,10 @@ impl Trait {
                 _ => None,
             })
             .filter_map(|path| match resolver.resolve_path_in_type_ns_fully(db, path) {
-                Some(TypeNs::Trait(t)) => Some(t),
+                Some(TypeNs::TraitId(t)) => Some(t),
                 _ => None,
             })
+            .map(Trait::from)
             .collect()
     }
 
@@ -871,14 +872,9 @@ impl Trait {
 
     pub fn associated_type_by_name(self, db: &impl DefDatabase, name: &Name) -> Option<TypeAlias> {
         let trait_data = self.trait_data(db);
-        trait_data
-            .items
-            .iter()
-            .filter_map(|item| match item {
-                AssocItemId::TypeAliasId(t) => Some(TypeAlias::from(*t)),
-                _ => None,
-            })
-            .find(|t| &t.name(db) == name)
+        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(
diff --git a/crates/ra_hir/src/expr.rs b/crates/ra_hir/src/expr.rs
index 869879bdf..8c4c63fda 100644
--- a/crates/ra_hir/src/expr.rs
+++ b/crates/ra_hir/src/expr.rs
@@ -46,7 +46,7 @@ pub(crate) fn resolver_for_scope(
     let scopes = owner.expr_scopes(db);
     let scope_chain = scopes.scope_chain(scope_id).collect::<Vec<_>>();
     for scope in scope_chain.into_iter().rev() {
-        r = r.push_expr_scope(owner, Arc::clone(&scopes), scope);
+        r = r.push_expr_scope(owner.into(), Arc::clone(&scopes), scope);
     }
     r
 }
@@ -152,7 +152,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
             _ => return,
         };
 
-        let std_result_ctor = TypeCtor::Adt(Adt::Enum(std_result_enum));
+        let std_result_ctor = TypeCtor::Adt(Adt::Enum(std_result_enum.into()));
         let params = match &mismatch.expected {
             Ty::Apply(ApplicationTy { ctor, parameters }) if ctor == &std_result_ctor => parameters,
             _ => return,
diff --git a/crates/ra_hir/src/from_id.rs b/crates/ra_hir/src/from_id.rs
index b7692d407..7042422cc 100644
--- a/crates/ra_hir/src/from_id.rs
+++ b/crates/ra_hir/src/from_id.rs
@@ -3,9 +3,14 @@
 //! It's unclear if we need this long-term, but it's definitelly useful while we
 //! are splitting the hir.
 
-use hir_def::{AdtId, AssocItemId, DefWithBodyId, EnumVariantId, GenericDefId, ModuleDefId};
+use hir_def::{
+    AdtId, AssocItemId, DefWithBodyId, EnumId, EnumVariantId, GenericDefId, ModuleDefId, StructId,
+    TypeAliasId, UnionId,
+};
 
-use crate::{Adt, AssocItem, DefWithBody, EnumVariant, GenericDef, ModuleDef};
+use crate::{
+    ty::TypableDef, Adt, AssocItem, DefWithBody, EnumVariant, GenericDef, ModuleDef, TypeAlias,
+};
 
 macro_rules! from_id {
     ($(($id:path, $ty:path)),*) => {$(
@@ -83,6 +88,16 @@ impl From<DefWithBody> for DefWithBodyId {
     }
 }
 
+impl From<DefWithBodyId> for DefWithBody {
+    fn from(def: DefWithBodyId) -> Self {
+        match def {
+            DefWithBodyId::FunctionId(it) => DefWithBody::Function(it.into()),
+            DefWithBodyId::StaticId(it) => DefWithBody::Static(it.into()),
+            DefWithBodyId::ConstId(it) => DefWithBody::Const(it.into()),
+        }
+    }
+}
+
 impl From<AssocItemId> for AssocItem {
     fn from(def: AssocItemId) -> Self {
         match def {
@@ -122,3 +137,49 @@ impl From<GenericDefId> for GenericDef {
         }
     }
 }
+
+impl From<AdtId> for TypableDef {
+    fn from(id: AdtId) -> Self {
+        Adt::from(id).into()
+    }
+}
+
+impl From<StructId> for TypableDef {
+    fn from(id: StructId) -> Self {
+        AdtId::StructId(id).into()
+    }
+}
+
+impl From<UnionId> for TypableDef {
+    fn from(id: UnionId) -> Self {
+        AdtId::UnionId(id).into()
+    }
+}
+
+impl From<EnumId> for TypableDef {
+    fn from(id: EnumId) -> Self {
+        AdtId::EnumId(id).into()
+    }
+}
+
+impl From<EnumVariantId> for TypableDef {
+    fn from(id: EnumVariantId) -> Self {
+        EnumVariant::from(id).into()
+    }
+}
+
+impl From<TypeAliasId> for TypableDef {
+    fn from(id: TypeAliasId) -> Self {
+        TypeAlias::from(id).into()
+    }
+}
+
+impl From<Adt> for GenericDefId {
+    fn from(id: Adt) -> Self {
+        match id {
+            Adt::Struct(it) => it.id.into(),
+            Adt::Union(it) => it.id.into(),
+            Adt::Enum(it) => it.id.into(),
+        }
+    }
+}
diff --git a/crates/ra_hir/src/resolve.rs b/crates/ra_hir/src/resolve.rs
index eca8e0596..f4165babd 100644
--- a/crates/ra_hir/src/resolve.rs
+++ b/crates/ra_hir/src/resolve.rs
@@ -3,19 +3,21 @@ use std::sync::Arc;
 
 use hir_def::{
     builtin_type::BuiltinType,
+    db::DefDatabase2,
+    generics::GenericParams,
     nameres::CrateDefMap,
     path::{Path, PathKind},
-    AdtId, CrateModuleId, ModuleDefId,
+    AdtId, CrateModuleId, DefWithBodyId, EnumId, EnumVariantId, GenericDefId, ImplId, ModuleDefId,
+    StructId, TraitId, TypeAliasId,
 };
 use hir_expand::name::{self, Name};
 use rustc_hash::FxHashSet;
 
 use crate::{
     code_model::Crate,
-    db::{DefDatabase, HirDatabase},
+    db::DefDatabase,
     expr::{ExprScopes, PatId, ScopeId},
-    generics::{GenericParams, HasGenericParams},
-    Adt, Const, Container, DefWithBody, Enum, EnumVariant, Function, GenericDef, ImplBlock, Local,
+    Adt, Const, Container, DefWithBody, EnumVariant, Function, GenericDef, ImplBlock, Local,
     MacroDef, Module, ModuleDef, PerNs, Static, Struct, Trait, TypeAlias,
 };
 
@@ -33,7 +35,7 @@ pub(crate) struct ModuleItemMap {
 
 #[derive(Debug, Clone)]
 pub(crate) struct ExprScope {
-    owner: DefWithBody,
+    owner: DefWithBodyId,
     expr_scopes: Arc<ExprScopes>,
     scope_id: ScopeId,
 }
@@ -43,28 +45,28 @@ pub(crate) enum Scope {
     /// All the items and imported names of a module
     ModuleScope(ModuleItemMap),
     /// Brings the generic parameters of an item into scope
-    GenericParams { def: GenericDef, params: Arc<GenericParams> },
+    GenericParams { def: GenericDefId, params: Arc<GenericParams> },
     /// Brings `Self` in `impl` block into scope
-    ImplBlockScope(ImplBlock),
+    ImplBlockScope(ImplId),
     /// Brings `Self` in enum, struct and union definitions into scope
-    AdtScope(Adt),
+    AdtScope(AdtId),
     /// Local bindings
     ExprScope(ExprScope),
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub(crate) enum TypeNs {
-    SelfType(ImplBlock),
+    SelfType(ImplId),
     GenericParam(u32),
-    Adt(Adt),
-    AdtSelfType(Adt),
-    EnumVariant(EnumVariant),
-    TypeAlias(TypeAlias),
+    AdtId(AdtId),
+    AdtSelfType(AdtId),
+    EnumVariantId(EnumVariantId),
+    TypeAliasId(TypeAliasId),
     BuiltinType(BuiltinType),
-    Trait(Trait),
+    TraitId(TraitId),
     // Module belong to type ns, but the resolver is used when all module paths
     // are fully resolved.
-    // Module(Module)
+    // ModuleId(ModuleId)
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
@@ -85,10 +87,14 @@ pub(crate) enum ValueNs {
 
 impl Resolver {
     /// Resolve known trait from std, like `std::futures::Future`
-    pub(crate) fn resolve_known_trait(&self, db: &impl HirDatabase, path: &Path) -> Option<Trait> {
+    pub(crate) fn resolve_known_trait(
+        &self,
+        db: &impl DefDatabase2,
+        path: &Path,
+    ) -> Option<TraitId> {
         let res = self.resolve_module_path(db, path).take_types()?;
         match res {
-            ModuleDefId::TraitId(it) => Some(it.into()),
+            ModuleDefId::TraitId(it) => Some(it),
             _ => None,
         }
     }
@@ -96,27 +102,27 @@ impl Resolver {
     /// Resolve known struct from std, like `std::boxed::Box`
     pub(crate) fn resolve_known_struct(
         &self,
-        db: &impl HirDatabase,
+        db: &impl DefDatabase2,
         path: &Path,
-    ) -> Option<Struct> {
+    ) -> Option<StructId> {
         let res = self.resolve_module_path(db, path).take_types()?;
         match res {
-            ModuleDefId::AdtId(AdtId::StructId(it)) => Some(it.into()),
+            ModuleDefId::AdtId(AdtId::StructId(it)) => Some(it),
             _ => None,
         }
     }
 
     /// Resolve known enum from std, like `std::result::Result`
-    pub(crate) fn resolve_known_enum(&self, db: &impl HirDatabase, path: &Path) -> Option<Enum> {
+    pub(crate) fn resolve_known_enum(&self, db: &impl DefDatabase2, path: &Path) -> Option<EnumId> {
         let res = self.resolve_module_path(db, path).take_types()?;
         match res {
-            ModuleDefId::AdtId(AdtId::EnumId(it)) => Some(it.into()),
+            ModuleDefId::AdtId(AdtId::EnumId(it)) => Some(it),
             _ => None,
         }
     }
 
     /// pub only for source-binder
-    pub(crate) fn resolve_module_path(&self, db: &impl HirDatabase, path: &Path) -> PerNs {
+    pub(crate) fn resolve_module_path(&self, db: &impl DefDatabase2, path: &Path) -> PerNs {
         let (item_map, module) = match self.module() {
             Some(it) => it,
             None => return PerNs::none(),
@@ -130,7 +136,7 @@ impl Resolver {
 
     pub(crate) fn resolve_path_in_type_ns(
         &self,
-        db: &impl HirDatabase,
+        db: &impl DefDatabase2,
         path: &Path,
     ) -> Option<(TypeNs, Option<usize>)> {
         if path.is_type_relative() {
@@ -164,13 +170,13 @@ impl Resolver {
                 Scope::ModuleScope(m) => {
                     let (module_def, idx) = m.crate_def_map.resolve_path(db, m.module_id, path);
                     let res = match module_def.take_types()? {
-                        ModuleDefId::AdtId(it) => TypeNs::Adt(it.into()),
-                        ModuleDefId::EnumVariantId(it) => TypeNs::EnumVariant(it.into()),
+                        ModuleDefId::AdtId(it) => TypeNs::AdtId(it),
+                        ModuleDefId::EnumVariantId(it) => TypeNs::EnumVariantId(it),
 
-                        ModuleDefId::TypeAliasId(it) => TypeNs::TypeAlias(it.into()),
+                        ModuleDefId::TypeAliasId(it) => TypeNs::TypeAliasId(it),
                         ModuleDefId::BuiltinType(it) => TypeNs::BuiltinType(it),
 
-                        ModuleDefId::TraitId(it) => TypeNs::Trait(it.into()),
+                        ModuleDefId::TraitId(it) => TypeNs::TraitId(it),
 
                         ModuleDefId::FunctionId(_)
                         | ModuleDefId::ConstId(_)
@@ -186,7 +192,7 @@ impl Resolver {
 
     pub(crate) fn resolve_path_in_type_ns_fully(
         &self,
-        db: &impl HirDatabase,
+        db: &impl DefDatabase2,
         path: &Path,
     ) -> Option<TypeNs> {
         let (res, unresolved) = self.resolve_path_in_type_ns(db, path)?;
@@ -198,7 +204,7 @@ impl Resolver {
 
     pub(crate) fn resolve_path_in_value_ns<'p>(
         &self,
-        db: &impl HirDatabase,
+        db: &impl DefDatabase2,
         path: &'p Path,
     ) -> Option<ResolveValueResult> {
         if path.is_type_relative() {
@@ -278,9 +284,9 @@ impl Resolver {
                         }
                         Some(idx) => {
                             let ty = match module_def.take_types()? {
-                                ModuleDefId::AdtId(it) => TypeNs::Adt(it.into()),
-                                ModuleDefId::TraitId(it) => TypeNs::Trait(it.into()),
-                                ModuleDefId::TypeAliasId(it) => TypeNs::TypeAlias(it.into()),
+                                ModuleDefId::AdtId(it) => TypeNs::AdtId(it),
+                                ModuleDefId::TraitId(it) => TypeNs::TraitId(it),
+                                ModuleDefId::TypeAliasId(it) => TypeNs::TypeAliasId(it),
                                 ModuleDefId::BuiltinType(it) => TypeNs::BuiltinType(it),
 
                                 ModuleDefId::ModuleId(_)
@@ -300,7 +306,7 @@ impl Resolver {
 
     pub(crate) fn resolve_path_in_value_ns_fully(
         &self,
-        db: &impl HirDatabase,
+        db: &impl DefDatabase2,
         path: &Path,
     ) -> Option<ValueNs> {
         match self.resolve_path_in_value_ns(db, path)? {
@@ -311,7 +317,7 @@ impl Resolver {
 
     pub(crate) fn resolve_path_as_macro(
         &self,
-        db: &impl DefDatabase,
+        db: &impl DefDatabase2,
         path: &Path,
     ) -> Option<MacroDef> {
         let (item_map, module) = self.module()?;
@@ -320,7 +326,7 @@ impl Resolver {
 
     pub(crate) fn process_all_names(
         &self,
-        db: &impl HirDatabase,
+        db: &impl DefDatabase2,
         f: &mut dyn FnMut(Name, ScopeDef),
     ) {
         for scope in self.scopes.iter().rev() {
@@ -328,16 +334,15 @@ impl Resolver {
         }
     }
 
-    pub(crate) fn traits_in_scope(&self, db: &impl HirDatabase) -> FxHashSet<Trait> {
+    pub(crate) fn traits_in_scope(&self, db: &impl DefDatabase2) -> FxHashSet<TraitId> {
         let mut traits = FxHashSet::default();
         for scope in &self.scopes {
             if let Scope::ModuleScope(m) = scope {
                 if let Some(prelude) = m.crate_def_map.prelude() {
                     let prelude_def_map = db.crate_def_map(prelude.krate);
-                    traits
-                        .extend(prelude_def_map[prelude.module_id].scope.traits().map(Trait::from));
+                    traits.extend(prelude_def_map[prelude.module_id].scope.traits());
                 }
-                traits.extend(m.crate_def_map[m.module_id].scope.traits().map(Trait::from));
+                traits.extend(m.crate_def_map[m.module_id].scope.traits());
             }
         }
         traits
@@ -367,7 +372,7 @@ impl Resolver {
             .flat_map(|params| params.where_predicates.iter())
     }
 
-    pub(crate) fn generic_def(&self) -> Option<crate::generics::GenericDef> {
+    pub(crate) fn generic_def(&self) -> Option<GenericDefId> {
         self.scopes.iter().find_map(|scope| match scope {
             Scope::GenericParams { def, .. } => Some(*def),
             _ => None,
@@ -383,10 +388,10 @@ impl Resolver {
 
     pub(crate) fn push_generic_params_scope(
         self,
-        db: &impl DefDatabase,
-        def: GenericDef,
+        db: &impl DefDatabase2,
+        def: GenericDefId,
     ) -> Resolver {
-        let params = def.generic_params(db);
+        let params = db.generic_params(def);
         if params.params.is_empty() {
             self
         } else {
@@ -394,7 +399,7 @@ impl Resolver {
         }
     }
 
-    pub(crate) fn push_impl_block_scope(self, impl_block: ImplBlock) -> Resolver {
+    pub(crate) fn push_impl_block_scope(self, impl_block: ImplId) -> Resolver {
         self.push_scope(Scope::ImplBlockScope(impl_block))
     }
 
@@ -408,7 +413,7 @@ impl Resolver {
 
     pub(crate) fn push_expr_scope(
         self,
-        owner: DefWithBody,
+        owner: DefWithBodyId,
         expr_scopes: Arc<ExprScopes>,
         scope_id: ScopeId,
     ) -> Resolver {
@@ -440,7 +445,7 @@ impl From<PerNs> for ScopeDef {
 }
 
 impl Scope {
-    fn process_names(&self, db: &impl HirDatabase, f: &mut dyn FnMut(Name, ScopeDef)) {
+    fn process_names(&self, db: &impl DefDatabase2, f: &mut dyn FnMut(Name, ScopeDef)) {
         match self {
             Scope::ModuleScope(m) => {
                 // FIXME: should we provide `self` here?
@@ -472,14 +477,14 @@ impl Scope {
                 }
             }
             Scope::ImplBlockScope(i) => {
-                f(name::SELF_TYPE, ScopeDef::ImplSelfType(*i));
+                f(name::SELF_TYPE, ScopeDef::ImplSelfType((*i).into()));
             }
             Scope::AdtScope(i) => {
-                f(name::SELF_TYPE, ScopeDef::AdtSelfType(*i));
+                f(name::SELF_TYPE, ScopeDef::AdtSelfType((*i).into()));
             }
             Scope::ExprScope(scope) => {
                 scope.expr_scopes.entries(scope.scope_id).iter().for_each(|e| {
-                    let local = Local { parent: scope.owner, pat_id: e.pat() };
+                    let local = Local { parent: scope.owner.into(), pat_id: e.pat() };
                     f(e.name().clone(), ScopeDef::Local(local));
                 });
             }
@@ -501,7 +506,7 @@ impl HasResolver for Module {
 
 impl HasResolver for Trait {
     fn resolver(self, db: &impl DefDatabase) -> Resolver {
-        self.module(db).resolver(db).push_generic_params_scope(db, self.into())
+        self.module(db).resolver(db).push_generic_params_scope(db, self.id.into())
     }
 }
 
@@ -511,7 +516,7 @@ impl<T: Into<Adt>> HasResolver for T {
         def.module(db)
             .resolver(db)
             .push_generic_params_scope(db, def.into())
-            .push_scope(Scope::AdtScope(def))
+            .push_scope(Scope::AdtScope(def.into()))
     }
 }
 
@@ -520,7 +525,7 @@ impl HasResolver for Function {
         self.container(db)
             .map(|c| c.resolver(db))
             .unwrap_or_else(|| self.module(db).resolver(db))
-            .push_generic_params_scope(db, self.into())
+            .push_generic_params_scope(db, self.id.into())
     }
 }
 
@@ -551,7 +556,7 @@ impl HasResolver for TypeAlias {
         self.container(db)
             .map(|ib| ib.resolver(db))
             .unwrap_or_else(|| self.module(db).resolver(db))
-            .push_generic_params_scope(db, self.into())
+            .push_generic_params_scope(db, self.id.into())
     }
 }
 
@@ -582,7 +587,7 @@ impl HasResolver for ImplBlock {
     fn resolver(self, db: &impl DefDatabase) -> Resolver {
         self.module(db)
             .resolver(db)
-            .push_generic_params_scope(db, self.into())
-            .push_impl_block_scope(self)
+            .push_generic_params_scope(db, self.id.into())
+            .push_impl_block_scope(self.id)
     }
 }
diff --git a/crates/ra_hir/src/source_binder.rs b/crates/ra_hir/src/source_binder.rs
index 727310f06..5abb8d693 100644
--- a/crates/ra_hir/src/source_binder.rs
+++ b/crates/ra_hir/src/source_binder.rs
@@ -25,8 +25,9 @@ use crate::{
     ids::LocationCtx,
     resolve::{HasResolver, ScopeDef, TypeNs, ValueNs},
     ty::method_resolution::{self, implements_trait},
-    AssocItem, Const, DefWithBody, Either, Enum, FromSource, Function, GenericParam, HasBody,
-    HirFileId, Local, MacroDef, Module, Name, Path, Resolver, Static, Struct, Ty,
+    Adt, AssocItem, Const, DefWithBody, Either, Enum, EnumVariant, FromSource, Function,
+    GenericParam, HasBody, HirFileId, Local, MacroDef, Module, Name, Path, Resolver, Static,
+    Struct, Trait, Ty, TypeAlias,
 };
 
 fn try_get_resolver_for_node(db: &impl HirDatabase, node: Source<&SyntaxNode>) -> Option<Resolver> {
@@ -240,16 +241,18 @@ impl SourceAnalyzer {
         path: &crate::Path,
     ) -> Option<PathResolution> {
         let types = self.resolver.resolve_path_in_type_ns_fully(db, &path).map(|ty| match ty {
-            TypeNs::SelfType(it) => PathResolution::SelfType(it),
+            TypeNs::SelfType(it) => PathResolution::SelfType(it.into()),
             TypeNs::GenericParam(idx) => PathResolution::GenericParam(GenericParam {
-                parent: self.resolver.generic_def().unwrap(),
+                parent: self.resolver.generic_def().unwrap().into(),
                 idx,
             }),
-            TypeNs::AdtSelfType(it) | TypeNs::Adt(it) => PathResolution::Def(it.into()),
-            TypeNs::EnumVariant(it) => PathResolution::Def(it.into()),
-            TypeNs::TypeAlias(it) => PathResolution::Def(it.into()),
+            TypeNs::AdtSelfType(it) | TypeNs::AdtId(it) => {
+                PathResolution::Def(Adt::from(it).into())
+            }
+            TypeNs::EnumVariantId(it) => PathResolution::Def(EnumVariant::from(it).into()),
+            TypeNs::TypeAliasId(it) => PathResolution::Def(TypeAlias::from(it).into()),
             TypeNs::BuiltinType(it) => PathResolution::Def(it.into()),
-            TypeNs::Trait(it) => PathResolution::Def(it.into()),
+            TypeNs::TraitId(it) => PathResolution::Def(Trait::from(it).into()),
         });
         let values = self.resolver.resolve_path_in_value_ns_fully(db, &path).and_then(|val| {
             let res = match val {
@@ -392,7 +395,7 @@ impl SourceAnalyzer {
         let std_future_path = known::std_future_future();
 
         let std_future_trait = match self.resolver.resolve_known_trait(db, &std_future_path) {
-            Some(it) => it,
+            Some(it) => it.into(),
             _ => return false,
         };
 
diff --git a/crates/ra_hir/src/ty/infer.rs b/crates/ra_hir/src/ty/infer.rs
index 7f9e81d64..684d66946 100644
--- a/crates/ra_hir/src/ty/infer.rs
+++ b/crates/ra_hir/src/ty/infer.rs
@@ -24,6 +24,7 @@ use rustc_hash::FxHashMap;
 use hir_def::{
     path::known,
     type_ref::{Mutability, TypeRef},
+    AdtId,
 };
 use hir_expand::{diagnostics::DiagnosticSink, name};
 use ra_arena::map::ArenaMap;
@@ -43,7 +44,7 @@ use crate::{
     resolve::{HasResolver, Resolver, TypeNs},
     ty::infer::diagnostics::InferenceDiagnostic,
     Adt, AssocItem, ConstData, DefWithBody, FloatTy, FnData, Function, HasBody, IntTy, Path,
-    StructField, VariantDef,
+    StructField, Trait, VariantDef,
 };
 
 macro_rules! ty_app {
@@ -518,17 +519,17 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             // 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::Adt(Adt::Struct(it))) => it.into(),
-                Some(TypeNs::Adt(Adt::Union(it))) => it.into(),
+                Some(TypeNs::AdtId(AdtId::StructId(it))) => it.into(),
+                Some(TypeNs::AdtId(AdtId::UnionId(it))) => it.into(),
                 Some(TypeNs::AdtSelfType(adt)) => adt.into(),
-                Some(TypeNs::EnumVariant(it)) => it.into(),
-                Some(TypeNs::TypeAlias(it)) => it.into(),
+                Some(TypeNs::EnumVariantId(it)) => it.into(),
+                Some(TypeNs::TypeAliasId(it)) => it.into(),
 
                 Some(TypeNs::SelfType(_)) |
                 Some(TypeNs::GenericParam(_)) |
                 Some(TypeNs::BuiltinType(_)) |
-                Some(TypeNs::Trait(_)) |
-                Some(TypeNs::Adt(Adt::Enum(_))) |
+                Some(TypeNs::TraitId(_)) |
+                Some(TypeNs::AdtId(AdtId::EnumId(_))) |
                 None => {
                     return (Ty::Unknown, None)
                 }
@@ -576,26 +577,26 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
     fn resolve_into_iter_item(&self) -> Option<TypeAlias> {
         let path = known::std_iter_into_iterator();
-        let trait_ = self.resolver.resolve_known_trait(self.db, &path)?;
+        let trait_: Trait = self.resolver.resolve_known_trait(self.db, &path)?.into();
         trait_.associated_type_by_name(self.db, &name::ITEM_TYPE)
     }
 
     fn resolve_ops_try_ok(&self) -> Option<TypeAlias> {
         let path = known::std_ops_try();
-        let trait_ = self.resolver.resolve_known_trait(self.db, &path)?;
+        let trait_: Trait = self.resolver.resolve_known_trait(self.db, &path)?.into();
         trait_.associated_type_by_name(self.db, &name::OK_TYPE)
     }
 
     fn resolve_future_future_output(&self) -> Option<TypeAlias> {
         let path = known::std_future_future();
-        let trait_ = self.resolver.resolve_known_trait(self.db, &path)?;
+        let trait_: Trait = self.resolver.resolve_known_trait(self.db, &path)?.into();
         trait_.associated_type_by_name(self.db, &name::OUTPUT_TYPE)
     }
 
     fn resolve_boxed_box(&self) -> Option<Adt> {
         let path = known::std_boxed_box();
         let struct_ = self.resolver.resolve_known_struct(self.db, &path)?;
-        Some(Adt::Struct(struct_))
+        Some(Adt::Struct(struct_.into()))
     }
 }
 
diff --git a/crates/ra_hir/src/ty/infer/path.rs b/crates/ra_hir/src/ty/infer/path.rs
index 31ca675aa..f36a27929 100644
--- a/crates/ra_hir/src/ty/infer/path.rs
+++ b/crates/ra_hir/src/ty/infer/path.rs
@@ -94,13 +94,13 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         let is_before_last = remaining_segments.len() == 1;
 
         match (def, is_before_last) {
-            (TypeNs::Trait(trait_), true) => {
+            (TypeNs::TraitId(trait_), true) => {
                 let segment =
                     remaining_segments.last().expect("there should be at least one segment here");
                 let trait_ref = TraitRef::from_resolved_path(
                     self.db,
                     &self.resolver,
-                    trait_,
+                    trait_.into(),
                     resolved_segment,
                     None,
                 );
diff --git a/crates/ra_hir/src/ty/lower.rs b/crates/ra_hir/src/ty/lower.rs
index 397ee7d5f..d4fbddac0 100644
--- a/crates/ra_hir/src/ty/lower.rs
+++ b/crates/ra_hir/src/ty/lower.rs
@@ -28,8 +28,8 @@ use crate::{
         Adt,
     },
     util::make_mut_slice,
-    Const, Enum, EnumVariant, Function, ModuleDef, Path, Static, Struct, StructField, Trait,
-    TypeAlias, Union, VariantDef,
+    Const, Enum, EnumVariant, Function, ImplBlock, ModuleDef, Path, Static, Struct, StructField,
+    Trait, TypeAlias, Union, VariantDef,
 };
 
 // FIXME: this is only really used in `type_for_def`, which contains a bunch of
@@ -156,9 +156,14 @@ impl Ty {
         remaining_segments: &[PathSegment],
     ) -> Ty {
         let ty = match resolution {
-            TypeNs::Trait(trait_) => {
-                let trait_ref =
-                    TraitRef::from_resolved_path(db, resolver, trait_, resolved_segment, None);
+            TypeNs::TraitId(trait_) => {
+                let trait_ref = TraitRef::from_resolved_path(
+                    db,
+                    resolver,
+                    trait_.into(),
+                    resolved_segment,
+                    None,
+                );
                 return if remaining_segments.len() == 1 {
                     let segment = &remaining_segments[0];
                     match trait_ref
@@ -189,18 +194,18 @@ impl Ty {
                 let name = resolved_segment.name.clone();
                 Ty::Param { idx, name }
             }
-            TypeNs::SelfType(impl_block) => impl_block.target_ty(db),
-            TypeNs::AdtSelfType(adt) => adt.ty(db),
+            TypeNs::SelfType(impl_block) => ImplBlock::from(impl_block).target_ty(db),
+            TypeNs::AdtSelfType(adt) => Adt::from(adt).ty(db),
 
-            TypeNs::Adt(it) => Ty::from_hir_path_inner(db, resolver, resolved_segment, it.into()),
+            TypeNs::AdtId(it) => Ty::from_hir_path_inner(db, resolver, resolved_segment, it.into()),
             TypeNs::BuiltinType(it) => {
                 Ty::from_hir_path_inner(db, resolver, resolved_segment, it.into())
             }
-            TypeNs::TypeAlias(it) => {
+            TypeNs::TypeAliasId(it) => {
                 Ty::from_hir_path_inner(db, resolver, resolved_segment, it.into())
             }
             // FIXME: report error
-            TypeNs::EnumVariant(_) => return Ty::Unknown,
+            TypeNs::EnumVariantId(_) => return Ty::Unknown,
         };
 
         Ty::from_type_relative_path(db, resolver, ty, remaining_segments)
@@ -247,7 +252,7 @@ impl Ty {
             Some(def) => def,
             None => return Ty::Unknown, // this can't actually happen
         };
-        let predicates = db.generic_predicates_for_param(def, param_idx);
+        let predicates = db.generic_predicates_for_param(def.into(), param_idx);
         let traits_from_env = predicates.iter().filter_map(|pred| match pred {
             GenericPredicate::Implemented(tr) if tr.self_ty() == &self_ty => Some(tr.trait_),
             _ => None,
@@ -391,11 +396,11 @@ impl TraitRef {
         explicit_self_ty: Option<Ty>,
     ) -> Option<Self> {
         let resolved = match resolver.resolve_path_in_type_ns_fully(db, &path)? {
-            TypeNs::Trait(tr) => tr,
+            TypeNs::TraitId(tr) => tr,
             _ => return None,
         };
         let segment = path.segments.last().expect("path should have at least one segment");
-        Some(TraitRef::from_resolved_path(db, resolver, resolved, segment, explicit_self_ty))
+        Some(TraitRef::from_resolved_path(db, resolver, resolved.into(), segment, explicit_self_ty))
     }
 
     pub(super) fn from_resolved_path(
diff --git a/crates/ra_hir/src/ty/method_resolution.rs b/crates/ra_hir/src/ty/method_resolution.rs
index f377fca48..26dd06171 100644
--- a/crates/ra_hir/src/ty/method_resolution.rs
+++ b/crates/ra_hir/src/ty/method_resolution.rs
@@ -224,7 +224,9 @@ fn iterate_trait_method_candidates<T>(
         .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));
+    let traits = inherent_trait
+        .chain(traits_from_env)
+        .chain(resolver.traits_in_scope(db).into_iter().map(Trait::from));
     'traits: for t in traits {
         let data = t.trait_data(db);
 
diff --git a/crates/ra_hir_def/src/traits.rs b/crates/ra_hir_def/src/traits.rs
index 877d73d66..6c2d5b2a9 100644
--- a/crates/ra_hir_def/src/traits.rs
+++ b/crates/ra_hir_def/src/traits.rs
@@ -11,7 +11,7 @@ use ra_syntax::ast::{self, NameOwner};
 
 use crate::{
     db::DefDatabase2, AssocItemId, AstItemDef, ConstLoc, ContainerId, FunctionLoc, Intern, TraitId,
-    TypeAliasLoc,
+    TypeAliasId, TypeAliasLoc,
 };
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -56,4 +56,11 @@ impl TraitData {
         };
         Arc::new(TraitData { name, items, auto })
     }
+
+    pub fn associated_types(&self) -> impl Iterator<Item = TypeAliasId> + '_ {
+        self.items.iter().filter_map(|item| match item {
+            AssocItemId::TypeAliasId(t) => Some(*t),
+            _ => None,
+        })
+    }
 }