19 files changed, 493 insertions, 327 deletions

diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index a132d128b..92860fb59 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -10,10 +10,12 @@ use hir_def::{
     adt::VariantData,
     body::scope::ExprScopes,
     builtin_type::BuiltinType,
+    nameres::per_ns::PerNs,
+    resolver::{HasResolver, TypeNs},
     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,
@@ -30,9 +32,8 @@ use crate::{
         AstItemDef, ConstId, EnumId, FunctionId, MacroDefId, StaticId, StructId, TraitId,
         TypeAliasId,
     },
-    resolve::{HasResolver, TypeNs},
     ty::{InferenceResult, Namespace, TraitRef},
-    Either, HasSource, ImportId, Name, ScopeDef, Source, Ty,
+    Either, HasSource, ImportId, Name, Source, Ty,
 };
 
 /// hir::Crate describes a single crate. It's the main interface with which
@@ -829,7 +830,7 @@ impl Trait {
     }
 
     fn direct_super_traits(self, db: &impl HirDatabase) -> Vec<Trait> {
-        let resolver = self.resolver(db);
+        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
@@ -842,9 +843,10 @@ 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 +873,9 @@ 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(
@@ -1068,3 +1065,26 @@ pub struct GenericParam {
 pub struct ImplBlock {
     pub(crate) id: ImplId,
 }
+
+/// For IDE only
+pub enum ScopeDef {
+    ModuleDef(ModuleDef),
+    MacroDef(MacroDef),
+    GenericParam(GenericParam),
+    ImplSelfType(ImplBlock),
+    AdtSelfType(Adt),
+    Local(Local),
+    Unknown,
+}
+
+impl From<PerNs> for ScopeDef {
+    fn from(def: PerNs) -> Self {
+        def.take_types()
+            .or_else(|| def.take_values())
+            .map(|module_def_id| ScopeDef::ModuleDef(module_def_id.into()))
+            .or_else(|| {
+                def.get_macros().map(|macro_def_id| ScopeDef::MacroDef(macro_def_id.into()))
+            })
+            .unwrap_or(ScopeDef::Unknown)
+    }
+}
diff --git a/crates/ra_hir/src/expr.rs b/crates/ra_hir/src/expr.rs
index 869879bdf..6b703d8b4 100644
--- a/crates/ra_hir/src/expr.rs
+++ b/crates/ra_hir/src/expr.rs
@@ -2,7 +2,7 @@
 
 use std::sync::Arc;
 
-use hir_def::path::known;
+use hir_def::{path::known, resolver::HasResolver};
 use hir_expand::diagnostics::DiagnosticSink;
 use ra_syntax::ast;
 use ra_syntax::AstPtr;
@@ -11,9 +11,8 @@ use rustc_hash::FxHashSet;
 use crate::{
     db::HirDatabase,
     diagnostics::{MissingFields, MissingOkInTailExpr},
-    resolve::HasResolver,
     ty::{ApplicationTy, InferenceResult, Ty, TypeCtor},
-    Adt, DefWithBody, Function, HasBody, Name, Path, Resolver,
+    Adt, Function, Name, Path,
 };
 
 pub use hir_def::{
@@ -27,30 +26,6 @@ pub use hir_def::{
     },
 };
 
-// needs arbitrary_self_types to be a method... or maybe move to the def?
-pub(crate) fn resolver_for_expr(
-    db: &impl HirDatabase,
-    owner: DefWithBody,
-    expr_id: ExprId,
-) -> Resolver {
-    let scopes = owner.expr_scopes(db);
-    resolver_for_scope(db, owner, scopes.scope_for(expr_id))
-}
-
-pub(crate) fn resolver_for_scope(
-    db: &impl HirDatabase,
-    owner: DefWithBody,
-    scope_id: Option<ScopeId>,
-) -> Resolver {
-    let mut r = owner.resolver(db);
-    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
-}
-
 pub(crate) struct ExprValidator<'a, 'b: 'a> {
     func: Function,
     infer: Arc<InferenceResult>,
@@ -146,13 +121,13 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
 
         let std_result_path = known::std_result_result();
 
-        let resolver = self.func.resolver(db);
+        let resolver = self.func.id.resolver(db);
         let std_result_enum = match resolver.resolve_known_enum(db, &std_result_path) {
             Some(it) => it,
             _ => 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..a3e9d8525 100644
--- a/crates/ra_hir/src/from_id.rs
+++ b/crates/ra_hir/src/from_id.rs
@@ -3,9 +3,21 @@
 //! 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, ConstId, DefWithBodyId, EnumId, EnumVariantId, FunctionId, GenericDefId,
+    ModuleDefId, StaticId, StructId, TypeAliasId, UnionId,
+};
 
-use crate::{Adt, AssocItem, DefWithBody, EnumVariant, GenericDef, ModuleDef};
+use crate::{
+    ty::TypableDef, Adt, AssocItem, Const, Crate, DefWithBody, EnumVariant, Function, GenericDef,
+    ModuleDef, Static, TypeAlias,
+};
+
+impl From<ra_db::CrateId> for Crate {
+    fn from(crate_id: ra_db::CrateId) -> Self {
+        Crate { crate_id }
+    }
+}
 
 macro_rules! from_id {
     ($(($id:path, $ty:path)),*) => {$(
@@ -83,6 +95,16 @@ 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 +144,65 @@ 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<FunctionId> for TypableDef {
+    fn from(id: FunctionId) -> Self {
+        Function::from(id).into()
+    }
+}
+impl From<ConstId> for TypableDef {
+    fn from(id: ConstId) -> Self {
+        Const::from(id).into()
+    }
+}
+impl From<StaticId> for TypableDef {
+    fn from(id: StaticId) -> Self {
+        Static::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/impl_block.rs b/crates/ra_hir/src/impl_block.rs
index 964a3da8c..774fa1d96 100644
--- a/crates/ra_hir/src/impl_block.rs
+++ b/crates/ra_hir/src/impl_block.rs
@@ -1,11 +1,10 @@
 //! FIXME: write short doc here
 
-use hir_def::{type_ref::TypeRef, AstItemDef};
-use ra_syntax::ast::{self};
+use hir_def::{resolver::HasResolver, type_ref::TypeRef, AstItemDef};
+use ra_syntax::ast;
 
 use crate::{
     db::{AstDatabase, DefDatabase, HirDatabase},
-    resolve::HasResolver,
     ty::Ty,
     AssocItem, Crate, HasSource, ImplBlock, Module, Source, TraitRef,
 };
@@ -27,12 +26,12 @@ impl ImplBlock {
     }
 
     pub fn target_ty(&self, db: &impl HirDatabase) -> Ty {
-        Ty::from_hir(db, &self.resolver(db), &self.target_type(db))
+        Ty::from_hir(db, &self.id.resolver(db), &self.target_type(db))
     }
 
     pub fn target_trait_ref(&self, db: &impl HirDatabase) -> Option<TraitRef> {
         let target_ty = self.target_ty(db);
-        TraitRef::from_hir(db, &self.resolver(db), &self.target_trait(db)?, Some(target_ty))
+        TraitRef::from_hir(db, &self.id.resolver(db), &self.target_trait(db)?, Some(target_ty))
     }
 
     pub fn items(&self, db: &impl DefDatabase) -> Vec<AssocItem> {
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index 31da74d2f..76c96bdcf 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -38,7 +38,6 @@ mod impl_block;
 mod expr;
 mod lang_item;
 pub mod generics;
-mod resolve;
 pub mod diagnostics;
 mod util;
 
@@ -52,8 +51,6 @@ mod test_db;
 #[cfg(test)]
 mod marks;
 
-use crate::resolve::Resolver;
-
 pub use crate::{
     code_model::{
         attrs::{AttrDef, Attrs},
@@ -61,14 +58,13 @@ pub use crate::{
         src::{HasBodySource, HasSource},
         Adt, AssocItem, Const, ConstData, Container, Crate, CrateDependency, DefWithBody, Enum,
         EnumVariant, FieldSource, FnData, Function, GenericParam, HasBody, ImplBlock, Local,
-        MacroDef, Module, ModuleDef, ModuleSource, Static, Struct, StructField, Trait, TypeAlias,
-        Union, VariantDef,
+        MacroDef, Module, ModuleDef, ModuleSource, ScopeDef, Static, Struct, StructField, Trait,
+        TypeAlias, Union, VariantDef,
     },
     expr::ExprScopes,
     from_source::FromSource,
     generics::GenericDef,
     ids::{HirFileId, MacroCallId, MacroCallLoc, MacroDefId, MacroFile},
-    resolve::ScopeDef,
     source_binder::{PathResolution, ScopeEntryWithSyntax, SourceAnalyzer},
     ty::{
         display::HirDisplay,
diff --git a/crates/ra_hir/src/source_binder.rs b/crates/ra_hir/src/source_binder.rs
index 727310f06..c42ceabdf 100644
--- a/crates/ra_hir/src/source_binder.rs
+++ b/crates/ra_hir/src/source_binder.rs
@@ -10,6 +10,8 @@ use std::sync::Arc;
 use hir_def::{
     expr::{ExprId, PatId},
     path::known,
+    resolver::{self, resolver_for_scope, HasResolver, Resolver, TypeNs, ValueNs},
+    DefWithBodyId,
 };
 use hir_expand::{name::AsName, AstId, MacroCallId, MacroCallLoc, MacroFileKind, Source};
 use ra_syntax::{
@@ -21,12 +23,12 @@ use ra_syntax::{
 
 use crate::{
     db::HirDatabase,
-    expr::{self, BodySourceMap, ExprScopes, ScopeId},
+    expr::{BodySourceMap, ExprScopes, ScopeId},
     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, ScopeDef, Static,
+    Struct, Trait, Ty, TypeAlias,
 };
 
 fn try_get_resolver_for_node(db: &impl HirDatabase, node: Source<&SyntaxNode>) -> Option<Resolver> {
@@ -34,23 +36,25 @@ fn try_get_resolver_for_node(db: &impl HirDatabase, node: Source<&SyntaxNode>) -
         match (node.value) {
             ast::Module(it) => {
                 let src = node.with_value(it);
-                Some(crate::Module::from_declaration(db, src)?.resolver(db))
+                Some(crate::Module::from_declaration(db, src)?.id.resolver(db))
             },
              ast::SourceFile(it) => {
                 let src = node.with_value(crate::ModuleSource::SourceFile(it));
-                Some(crate::Module::from_definition(db, src)?.resolver(db))
+                Some(crate::Module::from_definition(db, src)?.id.resolver(db))
             },
             ast::StructDef(it) => {
                 let src = node.with_value(it);
-                Some(Struct::from_source(db, src)?.resolver(db))
+                Some(Struct::from_source(db, src)?.id.resolver(db))
             },
             ast::EnumDef(it) => {
                 let src = node.with_value(it);
-                Some(Enum::from_source(db, src)?.resolver(db))
+                Some(Enum::from_source(db, src)?.id.resolver(db))
             },
             _ => match node.value.kind() {
                 FN_DEF | CONST_DEF | STATIC_DEF => {
-                    Some(def_with_body_from_child_node(db, node)?.resolver(db))
+                    let def = def_with_body_from_child_node(db, node)?;
+                    let def = DefWithBodyId::from(def);
+                    Some(def.resolver(db))
                 }
                 // FIXME add missing cases
                 _ => None
@@ -159,7 +163,7 @@ impl SourceAnalyzer {
                 None => scope_for(&scopes, &source_map, node),
                 Some(offset) => scope_for_offset(&scopes, &source_map, node.with_value(offset)),
             };
-            let resolver = expr::resolver_for_scope(db, def, scope);
+            let resolver = resolver_for_scope(db, def.into(), scope);
             SourceAnalyzer {
                 resolver,
                 body_owner: Some(def),
@@ -231,7 +235,7 @@ impl SourceAnalyzer {
     ) -> Option<MacroDef> {
         // This must be a normal source file rather than macro file.
         let path = macro_call.path().and_then(Path::from_ast)?;
-        self.resolver.resolve_path_as_macro(db, &path)
+        self.resolver.resolve_path_as_macro(db, &path).map(|it| it.into())
     }
 
     pub fn resolve_hir_path(
@@ -240,16 +244,18 @@ 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 {
@@ -257,11 +263,11 @@ impl SourceAnalyzer {
                     let var = Local { parent: self.body_owner?, pat_id };
                     PathResolution::Local(var)
                 }
-                ValueNs::Function(it) => PathResolution::Def(it.into()),
-                ValueNs::Const(it) => PathResolution::Def(it.into()),
-                ValueNs::Static(it) => PathResolution::Def(it.into()),
-                ValueNs::Struct(it) => PathResolution::Def(it.into()),
-                ValueNs::EnumVariant(it) => PathResolution::Def(it.into()),
+                ValueNs::FunctionId(it) => PathResolution::Def(Function::from(it).into()),
+                ValueNs::ConstId(it) => PathResolution::Def(Const::from(it).into()),
+                ValueNs::StaticId(it) => PathResolution::Def(Static::from(it).into()),
+                ValueNs::StructId(it) => PathResolution::Def(Struct::from(it).into()),
+                ValueNs::EnumVariantId(it) => PathResolution::Def(EnumVariant::from(it).into()),
             };
             Some(res)
         });
@@ -272,7 +278,9 @@ impl SourceAnalyzer {
             .take_types()
             .map(|it| PathResolution::Def(it.into()));
         types.or(values).or(items).or_else(|| {
-            self.resolver.resolve_path_as_macro(db, &path).map(|def| PathResolution::Macro(def))
+            self.resolver
+                .resolve_path_as_macro(db, &path)
+                .map(|def| PathResolution::Macro(def.into()))
         })
     }
 
@@ -307,7 +315,22 @@ impl SourceAnalyzer {
     }
 
     pub fn process_all_names(&self, db: &impl HirDatabase, f: &mut dyn FnMut(Name, ScopeDef)) {
-        self.resolver.process_all_names(db, f)
+        self.resolver.process_all_names(db, &mut |name, def| {
+            let def = match def {
+                resolver::ScopeDef::PerNs(it) => it.into(),
+                resolver::ScopeDef::ImplSelfType(it) => ScopeDef::ImplSelfType(it.into()),
+                resolver::ScopeDef::AdtSelfType(it) => ScopeDef::AdtSelfType(it.into()),
+                resolver::ScopeDef::GenericParam(idx) => {
+                    let parent = self.resolver.generic_def().unwrap().into();
+                    ScopeDef::GenericParam(GenericParam { parent, idx })
+                }
+                resolver::ScopeDef::Local(pat_id) => {
+                    let parent = self.resolver.body_owner().unwrap().into();
+                    ScopeDef::Local(Local { parent, pat_id })
+                }
+            };
+            f(name, def)
+        })
     }
 
     // FIXME: we only use this in `inline_local_variable` assist, ideally, we
@@ -392,7 +415,7 @@ 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,
         };
 
@@ -402,7 +425,7 @@ impl SourceAnalyzer {
         };
 
         let canonical_ty = crate::ty::Canonical { value: ty, num_vars: 0 };
-        implements_trait(&canonical_ty, db, &self.resolver, krate, std_future_trait)
+        implements_trait(&canonical_ty, db, &self.resolver, krate.into(), std_future_trait)
     }
 
     pub fn expand(
diff --git a/crates/ra_hir/src/ty/autoderef.rs b/crates/ra_hir/src/ty/autoderef.rs
index 872a4517d..5d8518041 100644
--- a/crates/ra_hir/src/ty/autoderef.rs
+++ b/crates/ra_hir/src/ty/autoderef.rs
@@ -5,11 +5,12 @@
 
 use std::iter::successors;
 
+use hir_def::resolver::Resolver;
 use hir_expand::name;
 use log::{info, warn};
 
 use super::{traits::Solution, Canonical, Substs, Ty, TypeWalk};
-use crate::{db::HirDatabase, generics::HasGenericParams, Resolver};
+use crate::{db::HirDatabase, generics::HasGenericParams};
 
 const AUTODEREF_RECURSION_LIMIT: usize = 10;
 
@@ -39,7 +40,7 @@ fn deref_by_trait(
     ty: &Canonical<Ty>,
 ) -> Option<Canonical<Ty>> {
     let krate = resolver.krate()?;
-    let deref_trait = match db.lang_item(krate, "deref".into())? {
+    let deref_trait = match db.lang_item(krate.into(), "deref".into())? {
         crate::lang_item::LangItemTarget::Trait(t) => t,
         _ => return None,
     };
@@ -71,7 +72,7 @@ fn deref_by_trait(
 
     let canonical = super::Canonical { num_vars: 1 + ty.num_vars, value: in_env };
 
-    let solution = db.trait_solve(krate, canonical)?;
+    let solution = db.trait_solve(krate.into(), canonical)?;
 
     match &solution {
         Solution::Unique(vars) => {
diff --git a/crates/ra_hir/src/ty/infer.rs b/crates/ra_hir/src/ty/infer.rs
index 7f9e81d64..69b13baef 100644
--- a/crates/ra_hir/src/ty/infer.rs
+++ b/crates/ra_hir/src/ty/infer.rs
@@ -23,7 +23,9 @@ use rustc_hash::FxHashMap;
 
 use hir_def::{
     path::known,
+    resolver::{HasResolver, Resolver, TypeNs},
     type_ref::{Mutability, TypeRef},
+    AdtId, DefWithBodyId,
 };
 use hir_expand::{diagnostics::DiagnosticSink, name};
 use ra_arena::map::ArenaMap;
@@ -40,10 +42,9 @@ use crate::{
     code_model::TypeAlias,
     db::HirDatabase,
     expr::{BindingAnnotation, Body, ExprId, PatId},
-    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 {
@@ -64,7 +65,7 @@ mod coerce;
 /// The entry point of type inference.
 pub fn infer_query(db: &impl HirDatabase, def: DefWithBody) -> Arc<InferenceResult> {
     let _p = profile("infer_query");
-    let resolver = def.resolver(db);
+    let resolver = DefWithBodyId::from(def).resolver(db);
     let mut ctx = InferenceContext::new(db, def, resolver);
 
     match def {
@@ -377,8 +378,9 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         for obligation in obligations {
             let in_env = InEnvironment::new(self.trait_env.clone(), obligation.clone());
             let canonicalized = self.canonicalizer().canonicalize_obligation(in_env);
-            let solution =
-                self.db.trait_solve(self.resolver.krate().unwrap(), canonicalized.value.clone());
+            let solution = self
+                .db
+                .trait_solve(self.resolver.krate().unwrap().into(), canonicalized.value.clone());
 
             match solution {
                 Some(Solution::Unique(substs)) => {
@@ -518,17 +520,17 @@ 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 +578,26 @@ 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/coerce.rs b/crates/ra_hir/src/ty/infer/coerce.rs
index 6ea135126..0772b9df5 100644
--- a/crates/ra_hir/src/ty/infer/coerce.rs
+++ b/crates/ra_hir/src/ty/infer/coerce.rs
@@ -4,19 +4,19 @@
 //!
 //! See: https://doc.rust-lang.org/nomicon/coercions.html
 
+use hir_def::resolver::Resolver;
 use rustc_hash::FxHashMap;
-
 use test_utils::tested_by;
 
-use super::{InferTy, InferenceContext, TypeVarValue};
 use crate::{
     db::HirDatabase,
     lang_item::LangItemTarget,
-    resolve::Resolver,
     ty::{autoderef, Substs, Ty, TypeCtor, TypeWalk},
     Adt, Mutability,
 };
 
+use super::{InferTy, InferenceContext, TypeVarValue};
+
 impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     /// Unify two types, but may coerce the first one to the second one
     /// using "implicit coercion rules" if needed.
@@ -49,8 +49,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         resolver: &Resolver,
     ) -> FxHashMap<(TypeCtor, TypeCtor), usize> {
         let krate = resolver.krate().unwrap();
-        let impls = match db.lang_item(krate, "coerce_unsized".into()) {
-            Some(LangItemTarget::Trait(trait_)) => db.impls_for_trait(krate, trait_),
+        let impls = match db.lang_item(krate.into(), "coerce_unsized".into()) {
+            Some(LangItemTarget::Trait(trait_)) => db.impls_for_trait(krate.into(), trait_),
             _ => return FxHashMap::default(),
         };
 
diff --git a/crates/ra_hir/src/ty/infer/expr.rs b/crates/ra_hir/src/ty/infer/expr.rs
index 5e68a1678..ac570075f 100644
--- a/crates/ra_hir/src/ty/infer/expr.rs
+++ b/crates/ra_hir/src/ty/infer/expr.rs
@@ -6,13 +6,13 @@ use std::sync::Arc;
 use hir_def::{
     builtin_type::Signedness,
     path::{GenericArg, GenericArgs},
+    resolver::resolver_for_expr,
 };
 use hir_expand::name;
 
-use super::{BindingMode, Expectation, InferenceContext, InferenceDiagnostic, TypeMismatch};
 use crate::{
     db::HirDatabase,
-    expr::{self, Array, BinaryOp, Expr, ExprId, Literal, Statement, UnaryOp},
+    expr::{Array, BinaryOp, Expr, ExprId, Literal, Statement, UnaryOp},
     generics::{GenericParams, HasGenericParams},
     ty::{
         autoderef, method_resolution, op, CallableDef, InferTy, IntTy, Mutability, Namespace,
@@ -22,6 +22,8 @@ use crate::{
     Adt, Name,
 };
 
+use super::{BindingMode, Expectation, InferenceContext, InferenceDiagnostic, TypeMismatch};
+
 impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     pub(super) fn infer_expr(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
         let ty = self.infer_expr_inner(tgt_expr, expected);
@@ -186,7 +188,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             }
             Expr::Path(p) => {
                 // FIXME this could be more efficient...
-                let resolver = expr::resolver_for_expr(self.db, self.owner, tgt_expr);
+                let resolver = resolver_for_expr(self.db, self.owner.into(), tgt_expr);
                 self.infer_path(&resolver, p, tgt_expr.into()).unwrap_or(Ty::Unknown)
             }
             Expr::Continue => Ty::simple(TypeCtor::Never),
diff --git a/crates/ra_hir/src/ty/infer/path.rs b/crates/ra_hir/src/ty/infer/path.rs
index 31ca675aa..70136e514 100644
--- a/crates/ra_hir/src/ty/infer/path.rs
+++ b/crates/ra_hir/src/ty/infer/path.rs
@@ -1,16 +1,19 @@
 //! Path expression resolution.
 
-use hir_def::path::PathSegment;
+use hir_def::{
+    path::PathSegment,
+    resolver::{ResolveValueResult, Resolver, TypeNs, ValueNs},
+};
 
-use super::{ExprOrPatId, InferenceContext, TraitRef};
 use crate::{
     db::HirDatabase,
     generics::HasGenericParams,
-    resolve::{ResolveValueResult, Resolver, TypeNs, ValueNs},
     ty::{method_resolution, Namespace, Substs, Ty, TypableDef, TypeWalk},
-    AssocItem, Container, Name, Path,
+    AssocItem, Container, Function, Name, Path,
 };
 
+use super::{ExprOrPatId, InferenceContext, TraitRef};
+
 impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     pub(super) fn infer_path(
         &mut self,
@@ -60,11 +63,11 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 let ty = self.resolve_ty_as_possible(&mut vec![], ty);
                 return Some(ty);
             }
-            ValueNs::Function(it) => it.into(),
-            ValueNs::Const(it) => it.into(),
-            ValueNs::Static(it) => it.into(),
-            ValueNs::Struct(it) => it.into(),
-            ValueNs::EnumVariant(it) => it.into(),
+            ValueNs::FunctionId(it) => it.into(),
+            ValueNs::ConstId(it) => it.into(),
+            ValueNs::StaticId(it) => it.into(),
+            ValueNs::StructId(it) => it.into(),
+            ValueNs::EnumVariantId(it) => it.into(),
         };
 
         let mut ty = self.db.type_for_def(typable, Namespace::Values);
@@ -94,13 +97,13 @@ 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,
                 );
@@ -160,8 +163,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             AssocItem::TypeAlias(_) => None,
         })?;
         let def = match item {
-            AssocItem::Function(f) => ValueNs::Function(f),
-            AssocItem::Const(c) => ValueNs::Const(c),
+            AssocItem::Function(f) => ValueNs::FunctionId(f.id),
+            AssocItem::Const(c) => ValueNs::ConstId(c.id),
             AssocItem::TypeAlias(_) => unreachable!(),
         };
         let substs = Substs::build_for_def(self.db, item)
@@ -193,8 +196,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             method_resolution::LookupMode::Path,
             move |_ty, item| {
                 let def = match item {
-                    AssocItem::Function(f) => ValueNs::Function(f),
-                    AssocItem::Const(c) => ValueNs::Const(c),
+                    AssocItem::Function(f) => ValueNs::FunctionId(f.id),
+                    AssocItem::Const(c) => ValueNs::ConstId(c.id),
                     AssocItem::TypeAlias(_) => unreachable!(),
                 };
                 let substs = match item.container(self.db) {
@@ -224,7 +227,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     }
 
     fn find_self_types(&self, def: &ValueNs, actual_def_ty: Ty) -> Option<Substs> {
-        if let ValueNs::Function(func) = def {
+        if let ValueNs::FunctionId(func) = def {
+            let func = Function::from(*func);
             // We only do the infer if parent has generic params
             let gen = func.generic_params(self.db);
             if gen.count_parent_params() == 0 {
diff --git a/crates/ra_hir/src/ty/lower.rs b/crates/ra_hir/src/ty/lower.rs
index 397ee7d5f..c6ad0811b 100644
--- a/crates/ra_hir/src/ty/lower.rs
+++ b/crates/ra_hir/src/ty/lower.rs
@@ -11,7 +11,9 @@ use std::sync::Arc;
 use hir_def::{
     builtin_type::{BuiltinFloat, BuiltinInt, BuiltinType},
     path::{GenericArg, PathSegment},
+    resolver::{HasResolver, Resolver, TypeNs},
     type_ref::{TypeBound, TypeRef},
+    GenericDefId,
 };
 
 use super::{
@@ -22,14 +24,13 @@ use crate::{
     db::HirDatabase,
     generics::HasGenericParams,
     generics::{GenericDef, WherePredicate},
-    resolve::{HasResolver, Resolver, TypeNs},
     ty::{
         primitive::{FloatTy, IntTy, Uncertain},
         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 +157,14 @@ 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 +195,18 @@ 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 +253,7 @@ 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 +397,11 @@ 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(
@@ -548,8 +554,8 @@ pub(crate) fn callable_item_sig(db: &impl HirDatabase, def: CallableDef) -> FnSi
 pub(crate) fn type_for_field(db: &impl HirDatabase, field: StructField) -> Ty {
     let parent_def = field.parent_def(db);
     let resolver = match parent_def {
-        VariantDef::Struct(it) => it.resolver(db),
-        VariantDef::EnumVariant(it) => it.parent_enum(db).resolver(db),
+        VariantDef::Struct(it) => it.id.resolver(db),
+        VariantDef::EnumVariant(it) => it.parent.id.resolver(db),
     };
     let var_data = parent_def.variant_data(db);
     let type_ref = &var_data.fields().unwrap()[field.id].type_ref;
@@ -569,7 +575,7 @@ pub(crate) fn generic_predicates_for_param_query(
     def: GenericDef,
     param_idx: u32,
 ) -> Arc<[GenericPredicate]> {
-    let resolver = def.resolver(db);
+    let resolver = GenericDefId::from(def).resolver(db);
     resolver
         .where_predicates_in_scope()
         // we have to filter out all other predicates *first*, before attempting to lower them
@@ -595,7 +601,7 @@ pub(crate) fn generic_predicates_query(
     db: &impl HirDatabase,
     def: GenericDef,
 ) -> Arc<[GenericPredicate]> {
-    let resolver = def.resolver(db);
+    let resolver = GenericDefId::from(def).resolver(db);
     resolver
         .where_predicates_in_scope()
         .flat_map(|pred| GenericPredicate::from_where_predicate(db, &resolver, pred))
@@ -604,7 +610,7 @@ pub(crate) fn generic_predicates_query(
 
 /// Resolve the default type params from generics
 pub(crate) fn generic_defaults_query(db: &impl HirDatabase, def: GenericDef) -> Substs {
-    let resolver = def.resolver(db);
+    let resolver = GenericDefId::from(def).resolver(db);
     let generic_params = def.generic_params(db);
 
     let defaults = generic_params
@@ -618,7 +624,7 @@ pub(crate) fn generic_defaults_query(db: &impl HirDatabase, def: GenericDef) ->
 
 fn fn_sig_for_fn(db: &impl HirDatabase, def: Function) -> FnSig {
     let data = def.data(db);
-    let resolver = def.resolver(db);
+    let resolver = def.id.resolver(db);
     let params = data.params().iter().map(|tr| Ty::from_hir(db, &resolver, tr)).collect::<Vec<_>>();
     let ret = Ty::from_hir(db, &resolver, data.ret_type());
     FnSig::from_params_and_return(params, ret)
@@ -635,7 +641,7 @@ fn type_for_fn(db: &impl HirDatabase, def: Function) -> Ty {
 /// Build the declared type of a const.
 fn type_for_const(db: &impl HirDatabase, def: Const) -> Ty {
     let data = def.data(db);
-    let resolver = def.resolver(db);
+    let resolver = def.id.resolver(db);
 
     Ty::from_hir(db, &resolver, data.type_ref())
 }
@@ -643,7 +649,7 @@ fn type_for_const(db: &impl HirDatabase, def: Const) -> Ty {
 /// Build the declared type of a static.
 fn type_for_static(db: &impl HirDatabase, def: Static) -> Ty {
     let data = def.data(db);
-    let resolver = def.resolver(db);
+    let resolver = def.id.resolver(db);
 
     Ty::from_hir(db, &resolver, data.type_ref())
 }
@@ -695,7 +701,7 @@ fn fn_sig_for_struct_constructor(db: &impl HirDatabase, def: Struct) -> FnSig {
         Some(fields) => fields,
         None => panic!("fn_sig_for_struct_constructor called on unit struct"),
     };
-    let resolver = def.resolver(db);
+    let resolver = def.id.resolver(db);
     let params = fields
         .iter()
         .map(|(_, field)| Ty::from_hir(db, &resolver, &field.type_ref))
@@ -721,7 +727,7 @@ fn fn_sig_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariant)
         Some(fields) => fields,
         None => panic!("fn_sig_for_enum_variant_constructor called for unit variant"),
     };
-    let resolver = def.parent_enum(db).resolver(db);
+    let resolver = def.parent.id.resolver(db);
     let params = fields
         .iter()
         .map(|(_, field)| Ty::from_hir(db, &resolver, &field.type_ref))
@@ -750,7 +756,7 @@ fn type_for_adt(db: &impl HirDatabase, adt: impl Into<Adt> + HasGenericParams) -
 
 fn type_for_type_alias(db: &impl HirDatabase, t: TypeAlias) -> Ty {
     let generics = t.generic_params(db);
-    let resolver = t.resolver(db);
+    let resolver = t.id.resolver(db);
     let type_ref = t.type_ref(db);
     let substs = Substs::identity(&generics);
     let inner = Ty::from_hir(db, &resolver, &type_ref.unwrap_or(TypeRef::Error));
diff --git a/crates/ra_hir/src/ty/method_resolution.rs b/crates/ra_hir/src/ty/method_resolution.rs
index f377fca48..64adb814d 100644
--- a/crates/ra_hir/src/ty/method_resolution.rs
+++ b/crates/ra_hir/src/ty/method_resolution.rs
@@ -5,11 +5,11 @@
 use std::sync::Arc;
 
 use arrayvec::ArrayVec;
+use hir_def::resolver::Resolver;
 use rustc_hash::FxHashMap;
 
 use crate::{
     db::HirDatabase,
-    resolve::Resolver,
     ty::primitive::{FloatBitness, Uncertain},
     ty::{Ty, TypeCtor},
     AssocItem, Crate, Function, ImplBlock, Module, Mutability, Name, Trait,
@@ -172,9 +172,14 @@ pub(crate) fn iterate_method_candidates<T>(
             // rustc does an autoderef and then autoref again).
 
             for derefed_ty in autoderef::autoderef(db, resolver, ty.clone()) {
-                if let Some(result) =
-                    iterate_inherent_methods(&derefed_ty, db, name, mode, krate, &mut callback)
-                {
+                if let Some(result) = iterate_inherent_methods(
+                    &derefed_ty,
+                    db,
+                    name,
+                    mode,
+                    krate.into(),
+                    &mut callback,
+                ) {
                     return Some(result);
                 }
                 if let Some(result) = iterate_trait_method_candidates(
@@ -192,7 +197,7 @@ pub(crate) fn iterate_method_candidates<T>(
         LookupMode::Path => {
             // No autoderef for path lookups
             if let Some(result) =
-                iterate_inherent_methods(&ty, db, name, mode, krate, &mut callback)
+                iterate_inherent_methods(&ty, db, name, mode, krate.into(), &mut callback)
             {
                 return Some(result);
             }
@@ -224,7 +229,9 @@ 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);
 
@@ -238,7 +245,7 @@ fn iterate_trait_method_candidates<T>(
             }
             if !known_implemented {
                 let goal = generic_implements_goal(db, env.clone(), t, ty.clone());
-                if db.trait_solve(krate, goal).is_none() {
+                if db.trait_solve(krate.into(), goal).is_none() {
                     continue 'traits;
                 }
             }
diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index a5bb60e85..77f091288 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -12,6 +12,7 @@ use ra_syntax::{
     },
     AstNode, AstPtr,
 };
+use test_utils::tested_by;
 
 use crate::{
     body::{Body, BodySourceMap, Expander, PatPtr},
@@ -153,6 +154,7 @@ where
                         None => self.collect_expr_opt(condition.expr()),
                         // if let -- desugar to match
                         Some(pat) => {
+                            tested_by!(infer_resolve_while_let);
                             let pat = self.collect_pat(pat);
                             let match_expr = self.collect_expr_opt(condition.expr());
                             let placeholder_pat = self.missing_pat();
diff --git a/crates/ra_hir_def/src/body/scope.rs b/crates/ra_hir_def/src/body/scope.rs
index aeb71ff22..5d7d17231 100644
--- a/crates/ra_hir_def/src/body/scope.rs
+++ b/crates/ra_hir_def/src/body/scope.rs
@@ -174,7 +174,7 @@ mod tests {
     use hir_expand::{name::AsName, Source};
     use ra_db::{fixture::WithFixture, FileId, SourceDatabase};
     use ra_syntax::{algo::find_node_at_offset, ast, AstNode};
-    use test_utils::{assert_eq_text, extract_offset};
+    use test_utils::{assert_eq_text, covers, extract_offset};
 
     use crate::{db::DefDatabase2, test_db::TestDB, FunctionId, ModuleDefId};
 
@@ -382,4 +382,20 @@ mod tests {
             53,
         );
     }
+
+    #[test]
+    fn infer_resolve_while_let() {
+        covers!(infer_resolve_while_let);
+        do_check_local_name(
+            r#"
+fn test() {
+    let foo: Option<f32> = None;
+    while let Option::Some(spam) = foo {
+        spam<|>
+    }
+}
+"#,
+            75,
+        );
+    }
 }
diff --git a/crates/ra_hir_def/src/lib.rs b/crates/ra_hir_def/src/lib.rs
index 0af41de87..d579f5c7e 100644
--- a/crates/ra_hir_def/src/lib.rs
+++ b/crates/ra_hir_def/src/lib.rs
@@ -19,6 +19,7 @@ pub mod expr;
 pub mod body;
 pub mod generics;
 pub mod traits;
+pub mod resolver;
 
 #[cfg(test)]
 mod test_db;
diff --git a/crates/ra_hir_def/src/marks.rs b/crates/ra_hir_def/src/marks.rs
index 0b99eac71..65239ca0a 100644
--- a/crates/ra_hir_def/src/marks.rs
+++ b/crates/ra_hir_def/src/marks.rs
@@ -11,4 +11,5 @@ test_utils::marks!(
     prelude_is_macro_use
     macro_dollar_crate_self
     macro_dollar_crate_other
+    infer_resolve_while_let
 );
diff --git a/crates/ra_hir/src/resolve.rs b/crates/ra_hir_def/src/resolver.rs
index eca8e0596..840785baa 100644
--- a/crates/ra_hir/src/resolve.rs
+++ b/crates/ra_hir_def/src/resolver.rs
@@ -1,26 +1,28 @@
-//! Name resolution.
+//! Name resolution façade.
 use std::sync::Arc;
 
-use hir_def::{
-    builtin_type::BuiltinType,
-    nameres::CrateDefMap,
-    path::{Path, PathKind},
-    AdtId, CrateModuleId, ModuleDefId,
+use hir_expand::{
+    name::{self, Name},
+    MacroDefId,
 };
-use hir_expand::name::{self, Name};
+use ra_db::CrateId;
 use rustc_hash::FxHashSet;
 
 use crate::{
-    code_model::Crate,
-    db::{DefDatabase, HirDatabase},
-    expr::{ExprScopes, PatId, ScopeId},
-    generics::{GenericParams, HasGenericParams},
-    Adt, Const, Container, DefWithBody, Enum, EnumVariant, Function, GenericDef, ImplBlock, Local,
-    MacroDef, Module, ModuleDef, PerNs, Static, Struct, Trait, TypeAlias,
+    body::scope::{ExprScopes, ScopeId},
+    builtin_type::BuiltinType,
+    db::DefDatabase2,
+    expr::{ExprId, PatId},
+    generics::GenericParams,
+    nameres::{per_ns::PerNs, CrateDefMap},
+    path::{Path, PathKind},
+    AdtId, AstItemDef, ConstId, ContainerId, CrateModuleId, DefWithBodyId, EnumId, EnumVariantId,
+    FunctionId, GenericDefId, ImplId, Lookup, ModuleDefId, ModuleId, StaticId, StructId, TraitId,
+    TypeAliasId, UnionId,
 };
 
 #[derive(Debug, Clone, Default)]
-pub(crate) struct Resolver {
+pub struct Resolver {
     scopes: Vec<Scope>,
 }
 
@@ -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,
 }
@@ -43,80 +45,76 @@ 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),
+pub enum TypeNs {
+    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)]
-pub(crate) enum ResolveValueResult {
+pub enum ResolveValueResult {
     ValueNs(ValueNs),
     Partial(TypeNs, usize),
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub(crate) enum ValueNs {
+pub enum ValueNs {
     LocalBinding(PatId),
-    Function(Function),
-    Const(Const),
-    Static(Static),
-    Struct(Struct),
-    EnumVariant(EnumVariant),
+    FunctionId(FunctionId),
+    ConstId(ConstId),
+    StaticId(StaticId),
+    StructId(StructId),
+    EnumVariantId(EnumVariantId),
 }
 
 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 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,
         }
     }
 
     /// Resolve known struct from std, like `std::boxed::Box`
-    pub(crate) fn resolve_known_struct(
-        &self,
-        db: &impl HirDatabase,
-        path: &Path,
-    ) -> Option<Struct> {
+    pub fn resolve_known_struct(&self, db: &impl DefDatabase2, path: &Path) -> 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 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 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(),
@@ -128,9 +126,9 @@ impl Resolver {
         module_res
     }
 
-    pub(crate) fn resolve_path_in_type_ns(
+    pub 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 +162,13 @@ 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(_)
@@ -184,9 +182,9 @@ impl Resolver {
         None
     }
 
-    pub(crate) fn resolve_path_in_type_ns_fully(
+    pub 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)?;
@@ -196,9 +194,9 @@ impl Resolver {
         Some(res)
     }
 
-    pub(crate) fn resolve_path_in_value_ns<'p>(
+    pub fn resolve_path_in_value_ns<'p>(
         &self,
-        db: &impl HirDatabase,
+        db: &impl DefDatabase2,
         path: &'p Path,
     ) -> Option<ResolveValueResult> {
         if path.is_type_relative() {
@@ -259,13 +257,11 @@ impl Resolver {
                     return match idx {
                         None => {
                             let value = match module_def.take_values()? {
-                                ModuleDefId::FunctionId(it) => ValueNs::Function(it.into()),
-                                ModuleDefId::AdtId(AdtId::StructId(it)) => {
-                                    ValueNs::Struct(it.into())
-                                }
-                                ModuleDefId::EnumVariantId(it) => ValueNs::EnumVariant(it.into()),
-                                ModuleDefId::ConstId(it) => ValueNs::Const(it.into()),
-                                ModuleDefId::StaticId(it) => ValueNs::Static(it.into()),
+                                ModuleDefId::FunctionId(it) => ValueNs::FunctionId(it),
+                                ModuleDefId::AdtId(AdtId::StructId(it)) => ValueNs::StructId(it),
+                                ModuleDefId::EnumVariantId(it) => ValueNs::EnumVariantId(it),
+                                ModuleDefId::ConstId(it) => ValueNs::ConstId(it),
+                                ModuleDefId::StaticId(it) => ValueNs::StaticId(it),
 
                                 ModuleDefId::AdtId(AdtId::EnumId(_))
                                 | ModuleDefId::AdtId(AdtId::UnionId(_))
@@ -278,9 +274,9 @@ 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(_)
@@ -298,9 +294,9 @@ impl Resolver {
         None
     }
 
-    pub(crate) fn resolve_path_in_value_ns_fully(
+    pub 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)? {
@@ -309,35 +305,26 @@ impl Resolver {
         }
     }
 
-    pub(crate) fn resolve_path_as_macro(
-        &self,
-        db: &impl DefDatabase,
-        path: &Path,
-    ) -> Option<MacroDef> {
+    pub fn resolve_path_as_macro(&self, db: &impl DefDatabase2, path: &Path) -> Option<MacroDefId> {
         let (item_map, module) = self.module()?;
-        item_map.resolve_path(db, module, path).0.get_macros().map(MacroDef::from)
+        item_map.resolve_path(db, module, path).0.get_macros()
     }
 
-    pub(crate) fn process_all_names(
-        &self,
-        db: &impl HirDatabase,
-        f: &mut dyn FnMut(Name, ScopeDef),
-    ) {
+    pub fn process_all_names(&self, db: &impl DefDatabase2, f: &mut dyn FnMut(Name, ScopeDef)) {
         for scope in self.scopes.iter().rev() {
             scope.process_names(db, f);
         }
     }
 
-    pub(crate) fn traits_in_scope(&self, db: &impl HirDatabase) -> FxHashSet<Trait> {
+    pub 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
@@ -351,11 +338,11 @@ impl Resolver {
         })
     }
 
-    pub(crate) fn krate(&self) -> Option<Crate> {
-        self.module().map(|t| Crate { crate_id: t.0.krate() })
+    pub fn krate(&self) -> Option<CrateId> {
+        self.module().map(|t| t.0.krate())
     }
 
-    pub(crate) fn where_predicates_in_scope<'a>(
+    pub fn where_predicates_in_scope<'a>(
         &'a self,
     ) -> impl Iterator<Item = &'a crate::generics::WherePredicate> + 'a {
         self.scopes
@@ -367,12 +354,19 @@ impl Resolver {
             .flat_map(|params| params.where_predicates.iter())
     }
 
-    pub(crate) fn generic_def(&self) -> Option<crate::generics::GenericDef> {
+    pub fn generic_def(&self) -> Option<GenericDefId> {
         self.scopes.iter().find_map(|scope| match scope {
             Scope::GenericParams { def, .. } => Some(*def),
             _ => None,
         })
     }
+
+    pub fn body_owner(&self) -> Option<DefWithBodyId> {
+        self.scopes.iter().find_map(|scope| match scope {
+            Scope::ExprScope(it) => Some(it.owner),
+            _ => None,
+        })
+    }
 }
 
 impl Resolver {
@@ -383,10 +377,10 @@ 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 +388,7 @@ 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 +402,7 @@ impl Resolver {
 
     pub(crate) fn push_expr_scope(
         self,
-        owner: DefWithBody,
+        owner: DefWithBodyId,
         expr_scopes: Arc<ExprScopes>,
         scope_id: ScopeId,
     ) -> Resolver {
@@ -416,31 +410,16 @@ impl Resolver {
     }
 }
 
-/// For IDE only
 pub enum ScopeDef {
-    ModuleDef(ModuleDef),
-    MacroDef(MacroDef),
+    PerNs(PerNs),
+    ImplSelfType(ImplId),
+    AdtSelfType(AdtId),
     GenericParam(u32),
-    ImplSelfType(ImplBlock),
-    AdtSelfType(Adt),
-    Local(Local),
-    Unknown,
-}
-
-impl From<PerNs> for ScopeDef {
-    fn from(def: PerNs) -> Self {
-        def.take_types()
-            .or_else(|| def.take_values())
-            .map(|module_def_id| ScopeDef::ModuleDef(module_def_id.into()))
-            .or_else(|| {
-                def.get_macros().map(|macro_def_id| ScopeDef::MacroDef(macro_def_id.into()))
-            })
-            .unwrap_or(ScopeDef::Unknown)
-    }
+    Local(PatId),
 }
 
 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?
@@ -451,18 +430,18 @@ impl Scope {
                 //     }),
                 // );
                 m.crate_def_map[m.module_id].scope.entries().for_each(|(name, res)| {
-                    f(name.clone(), res.def.into());
+                    f(name.clone(), ScopeDef::PerNs(res.def));
                 });
                 m.crate_def_map[m.module_id].scope.legacy_macros().for_each(|(name, macro_)| {
-                    f(name.clone(), ScopeDef::MacroDef(macro_.into()));
+                    f(name.clone(), ScopeDef::PerNs(PerNs::macros(macro_)));
                 });
                 m.crate_def_map.extern_prelude().iter().for_each(|(name, &def)| {
-                    f(name.clone(), ScopeDef::ModuleDef(def.into()));
+                    f(name.clone(), ScopeDef::PerNs(PerNs::types(def.into())));
                 });
                 if let Some(prelude) = m.crate_def_map.prelude() {
                     let prelude_def_map = db.crate_def_map(prelude.krate);
                     prelude_def_map[prelude.module_id].scope.entries().for_each(|(name, res)| {
-                        f(name.clone(), res.def.into());
+                        f(name.clone(), ScopeDef::PerNs(res.def));
                     });
                 }
             }
@@ -472,114 +451,155 @@ 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() };
-                    f(e.name().clone(), ScopeDef::Local(local));
+                    f(e.name().clone(), ScopeDef::Local(e.pat()));
                 });
             }
         }
     }
 }
 
-pub(crate) trait HasResolver {
+// needs arbitrary_self_types to be a method... or maybe move to the def?
+pub fn resolver_for_expr(
+    db: &impl DefDatabase2,
+    owner: DefWithBodyId,
+    expr_id: ExprId,
+) -> Resolver {
+    let scopes = db.expr_scopes(owner);
+    resolver_for_scope(db, owner, scopes.scope_for(expr_id))
+}
+
+pub fn resolver_for_scope(
+    db: &impl DefDatabase2,
+    owner: DefWithBodyId,
+    scope_id: Option<ScopeId>,
+) -> Resolver {
+    let mut r = owner.resolver(db);
+    let scopes = db.expr_scopes(owner);
+    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
+}
+
+pub trait HasResolver {
     /// Builds a resolver for type references inside this def.
-    fn resolver(self, db: &impl DefDatabase) -> Resolver;
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver;
 }
 
-impl HasResolver for Module {
-    fn resolver(self, db: &impl DefDatabase) -> Resolver {
-        let def_map = db.crate_def_map(self.id.krate);
-        Resolver::default().push_module_scope(def_map, self.id.module_id)
+impl HasResolver for ModuleId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        let def_map = db.crate_def_map(self.krate);
+        Resolver::default().push_module_scope(def_map, self.module_id)
     }
 }
 
-impl HasResolver for Trait {
-    fn resolver(self, db: &impl DefDatabase) -> Resolver {
+impl HasResolver for TraitId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
         self.module(db).resolver(db).push_generic_params_scope(db, self.into())
     }
 }
 
-impl<T: Into<Adt>> HasResolver for T {
-    fn resolver(self, db: &impl DefDatabase) -> Resolver {
-        let def = self.into();
-        def.module(db)
+impl HasResolver for AdtId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        let module = match self {
+            AdtId::StructId(it) => it.0.module(db),
+            AdtId::UnionId(it) => it.0.module(db),
+            AdtId::EnumId(it) => it.module(db),
+        };
+
+        module
             .resolver(db)
-            .push_generic_params_scope(db, def.into())
-            .push_scope(Scope::AdtScope(def))
+            .push_generic_params_scope(db, self.into())
+            .push_scope(Scope::AdtScope(self.into()))
     }
 }
 
-impl HasResolver for Function {
-    fn resolver(self, db: &impl DefDatabase) -> Resolver {
-        self.container(db)
-            .map(|c| c.resolver(db))
-            .unwrap_or_else(|| self.module(db).resolver(db))
-            .push_generic_params_scope(db, self.into())
+impl HasResolver for StructId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        AdtId::from(self).resolver(db)
+    }
+}
+
+impl HasResolver for UnionId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        AdtId::from(self).resolver(db)
+    }
+}
+
+impl HasResolver for EnumId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        AdtId::from(self).resolver(db)
     }
 }
 
-impl HasResolver for DefWithBody {
-    fn resolver(self, db: &impl DefDatabase) -> Resolver {
+impl HasResolver for FunctionId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        self.lookup(db).container.resolver(db).push_generic_params_scope(db, self.into())
+    }
+}
+
+impl HasResolver for DefWithBodyId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
         match self {
-            DefWithBody::Const(c) => c.resolver(db),
-            DefWithBody::Function(f) => f.resolver(db),
-            DefWithBody::Static(s) => s.resolver(db),
+            DefWithBodyId::ConstId(c) => c.resolver(db),
+            DefWithBodyId::FunctionId(f) => f.resolver(db),
+            DefWithBodyId::StaticId(s) => s.resolver(db),
         }
     }
 }
 
-impl HasResolver for Const {
-    fn resolver(self, db: &impl DefDatabase) -> Resolver {
-        self.container(db).map(|c| c.resolver(db)).unwrap_or_else(|| self.module(db).resolver(db))
+impl HasResolver for ConstId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        self.lookup(db).container.resolver(db)
     }
 }
 
-impl HasResolver for Static {
-    fn resolver(self, db: &impl DefDatabase) -> Resolver {
+impl HasResolver for StaticId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
         self.module(db).resolver(db)
     }
 }
 
-impl HasResolver for TypeAlias {
-    fn resolver(self, db: &impl DefDatabase) -> Resolver {
-        self.container(db)
-            .map(|ib| ib.resolver(db))
-            .unwrap_or_else(|| self.module(db).resolver(db))
-            .push_generic_params_scope(db, self.into())
+impl HasResolver for TypeAliasId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+        self.lookup(db).container.resolver(db).push_generic_params_scope(db, self.into())
     }
 }
 
-impl HasResolver for Container {
-    fn resolver(self, db: &impl DefDatabase) -> Resolver {
+impl HasResolver for ContainerId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
         match self {
-            Container::Trait(trait_) => trait_.resolver(db),
-            Container::ImplBlock(impl_block) => impl_block.resolver(db),
+            ContainerId::TraitId(it) => it.resolver(db),
+            ContainerId::ImplId(it) => it.resolver(db),
+            ContainerId::ModuleId(it) => it.resolver(db),
         }
     }
 }
 
-impl HasResolver for GenericDef {
-    fn resolver(self, db: &impl DefDatabase) -> crate::Resolver {
+impl HasResolver for GenericDefId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
         match self {
-            GenericDef::Function(inner) => inner.resolver(db),
-            GenericDef::Adt(adt) => adt.resolver(db),
-            GenericDef::Trait(inner) => inner.resolver(db),
-            GenericDef::TypeAlias(inner) => inner.resolver(db),
-            GenericDef::ImplBlock(inner) => inner.resolver(db),
-            GenericDef::EnumVariant(inner) => inner.parent_enum(db).resolver(db),
-            GenericDef::Const(inner) => inner.resolver(db),
+            GenericDefId::FunctionId(inner) => inner.resolver(db),
+            GenericDefId::AdtId(adt) => adt.resolver(db),
+            GenericDefId::TraitId(inner) => inner.resolver(db),
+            GenericDefId::TypeAliasId(inner) => inner.resolver(db),
+            GenericDefId::ImplId(inner) => inner.resolver(db),
+            GenericDefId::EnumVariantId(inner) => inner.parent.resolver(db),
+            GenericDefId::ConstId(inner) => inner.resolver(db),
         }
     }
 }
 
-impl HasResolver for ImplBlock {
-    fn resolver(self, db: &impl DefDatabase) -> Resolver {
+impl HasResolver for ImplId {
+    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
         self.module(db)
             .resolver(db)
             .push_generic_params_scope(db, self.into())
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,
+        })
+    }
 }