Merge branch 'master' of https://github.com/rust-analyzer/rust-analyzer into feature/themes

26 files changed, 1166 insertions, 693 deletions

diff --git a/crates/ra_hir_def/src/adt.rs b/crates/ra_hir_def/src/adt.rs
index d04f54e15..c9f30923e 100644
--- a/crates/ra_hir_def/src/adt.rs
+++ b/crates/ra_hir_def/src/adt.rs
@@ -2,13 +2,17 @@
 
 use std::sync::Arc;
 
-use hir_expand::name::{AsName, Name};
-use ra_arena::Arena;
+use hir_expand::{
+    either::Either,
+    name::{AsName, Name},
+    Source,
+};
+use ra_arena::{map::ArenaMap, Arena};
 use ra_syntax::ast::{self, NameOwner, TypeAscriptionOwner};
 
 use crate::{
-    db::DefDatabase2, type_ref::TypeRef, AstItemDef, EnumId, LocalEnumVariantId,
-    LocalStructFieldId, StructOrUnionId,
+    db::DefDatabase, trace::Trace, type_ref::TypeRef, AstItemDef, EnumId, HasChildSource,
+    LocalEnumVariantId, LocalStructFieldId, StructOrUnionId, VariantId,
 };
 
 /// Note that we use `StructData` for unions as well!
@@ -30,13 +34,9 @@ pub struct EnumVariantData {
     pub variant_data: Arc<VariantData>,
 }
 
-/// Fields of an enum variant or struct
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct VariantData(VariantDataInner);
-
 #[derive(Debug, Clone, PartialEq, Eq)]
-enum VariantDataInner {
-    Struct(Arena<LocalStructFieldId, StructFieldData>),
+pub enum VariantData {
+    Record(Arena<LocalStructFieldId, StructFieldData>),
     Tuple(Arena<LocalStructFieldId, StructFieldData>),
     Unit,
 }
@@ -49,10 +49,7 @@ pub struct StructFieldData {
 }
 
 impl StructData {
-    pub(crate) fn struct_data_query(
-        db: &impl DefDatabase2,
-        id: StructOrUnionId,
-    ) -> Arc<StructData> {
+    pub(crate) fn struct_data_query(db: &impl DefDatabase, id: StructOrUnionId) -> Arc<StructData> {
         let src = id.source(db);
         let name = src.value.name().map(|n| n.as_name());
         let variant_data = VariantData::new(src.value.kind());
@@ -62,20 +59,12 @@ impl StructData {
 }
 
 impl EnumData {
-    pub(crate) fn enum_data_query(db: &impl DefDatabase2, e: EnumId) -> Arc<EnumData> {
+    pub(crate) fn enum_data_query(db: &impl DefDatabase, e: EnumId) -> Arc<EnumData> {
         let src = e.source(db);
         let name = src.value.name().map(|n| n.as_name());
-        let variants = src
-            .value
-            .variant_list()
-            .into_iter()
-            .flat_map(|it| it.variants())
-            .map(|var| EnumVariantData {
-                name: var.name().map(|it| it.as_name()),
-                variant_data: Arc::new(VariantData::new(var.kind())),
-            })
-            .collect();
-        Arc::new(EnumData { name, variants })
+        let mut trace = Trace::new_for_arena();
+        lower_enum(&mut trace, &src.value);
+        Arc::new(EnumData { name, variants: trace.into_arena() })
     }
 
     pub(crate) fn variant(&self, name: &Name) -> Option<LocalEnumVariantId> {
@@ -84,39 +73,117 @@ impl EnumData {
     }
 }
 
+impl HasChildSource for EnumId {
+    type ChildId = LocalEnumVariantId;
+    type Value = ast::EnumVariant;
+    fn child_source(&self, db: &impl DefDatabase) -> Source<ArenaMap<Self::ChildId, Self::Value>> {
+        let src = self.source(db);
+        let mut trace = Trace::new_for_map();
+        lower_enum(&mut trace, &src.value);
+        src.with_value(trace.into_map())
+    }
+}
+
+fn lower_enum(
+    trace: &mut Trace<LocalEnumVariantId, EnumVariantData, ast::EnumVariant>,
+    ast: &ast::EnumDef,
+) {
+    for var in ast.variant_list().into_iter().flat_map(|it| it.variants()) {
+        trace.alloc(
+            || var.clone(),
+            || EnumVariantData {
+                name: var.name().map(|it| it.as_name()),
+                variant_data: Arc::new(VariantData::new(var.kind())),
+            },
+        );
+    }
+}
+
 impl VariantData {
     fn new(flavor: ast::StructKind) -> Self {
-        let inner = match flavor {
-            ast::StructKind::Tuple(fl) => {
-                let fields = fl
-                    .fields()
-                    .enumerate()
-                    .map(|(i, fd)| StructFieldData {
+        let mut trace = Trace::new_for_arena();
+        match lower_struct(&mut trace, &flavor) {
+            StructKind::Tuple => VariantData::Tuple(trace.into_arena()),
+            StructKind::Record => VariantData::Record(trace.into_arena()),
+            StructKind::Unit => VariantData::Unit,
+        }
+    }
+
+    pub fn fields(&self) -> &Arena<LocalStructFieldId, StructFieldData> {
+        const EMPTY: &Arena<LocalStructFieldId, StructFieldData> = &Arena::new();
+        match &self {
+            VariantData::Record(fields) | VariantData::Tuple(fields) => fields,
+            _ => EMPTY,
+        }
+    }
+
+    pub fn is_unit(&self) -> bool {
+        match self {
+            VariantData::Unit => true,
+            _ => false,
+        }
+    }
+}
+
+impl HasChildSource for VariantId {
+    type ChildId = LocalStructFieldId;
+    type Value = Either<ast::TupleFieldDef, ast::RecordFieldDef>;
+
+    fn child_source(&self, db: &impl DefDatabase) -> Source<ArenaMap<Self::ChildId, Self::Value>> {
+        let src = match self {
+            VariantId::EnumVariantId(it) => {
+                // I don't really like the fact that we call into parent source
+                // here, this might add to more queries then necessary.
+                let src = it.parent.child_source(db);
+                src.map(|map| map[it.local_id].kind())
+            }
+            VariantId::StructId(it) => it.0.source(db).map(|it| it.kind()),
+        };
+        let mut trace = Trace::new_for_map();
+        lower_struct(&mut trace, &src.value);
+        src.with_value(trace.into_map())
+    }
+}
+
+enum StructKind {
+    Tuple,
+    Record,
+    Unit,
+}
+
+fn lower_struct(
+    trace: &mut Trace<
+        LocalStructFieldId,
+        StructFieldData,
+        Either<ast::TupleFieldDef, ast::RecordFieldDef>,
+    >,
+    ast: &ast::StructKind,
+) -> StructKind {
+    match ast {
+        ast::StructKind::Tuple(fl) => {
+            for (i, fd) in fl.fields().enumerate() {
+                trace.alloc(
+                    || Either::A(fd.clone()),
+                    || StructFieldData {
                         name: Name::new_tuple_field(i),
                         type_ref: TypeRef::from_ast_opt(fd.type_ref()),
-                    })
-                    .collect();
-                VariantDataInner::Tuple(fields)
+                    },
+                );
             }
-            ast::StructKind::Named(fl) => {
-                let fields = fl
-                    .fields()
-                    .map(|fd| StructFieldData {
+            StructKind::Tuple
+        }
+        ast::StructKind::Record(fl) => {
+            for fd in fl.fields() {
+                trace.alloc(
+                    || Either::B(fd.clone()),
+                    || StructFieldData {
                         name: fd.name().map(|n| n.as_name()).unwrap_or_else(Name::missing),
                         type_ref: TypeRef::from_ast_opt(fd.ascribed_type()),
-                    })
-                    .collect();
-                VariantDataInner::Struct(fields)
+                    },
+                );
             }
-            ast::StructKind::Unit => VariantDataInner::Unit,
-        };
-        VariantData(inner)
-    }
-
-    pub fn fields(&self) -> Option<&Arena<LocalStructFieldId, StructFieldData>> {
-        match &self.0 {
-            VariantDataInner::Struct(fields) | VariantDataInner::Tuple(fields) => Some(fields),
-            _ => None,
+            StructKind::Record
         }
+        ast::StructKind::Unit => StructKind::Unit,
     }
 }
diff --git a/crates/ra_hir_def/src/attr.rs b/crates/ra_hir_def/src/attr.rs
index 0e961ca12..53456fc08 100644
--- a/crates/ra_hir_def/src/attr.rs
+++ b/crates/ra_hir_def/src/attr.rs
@@ -1,17 +1,93 @@
 //! A higher level attributes based on TokenTree, with also some shortcuts.
 
-use std::sync::Arc;
+use std::{ops, sync::Arc};
 
-use hir_expand::hygiene::Hygiene;
+use hir_expand::{either::Either, hygiene::Hygiene, AstId, Source};
 use mbe::ast_to_token_tree;
-use ra_cfg::CfgOptions;
 use ra_syntax::{
     ast::{self, AstNode, AttrsOwner},
     SmolStr,
 };
 use tt::Subtree;
 
-use crate::path::Path;
+use crate::{
+    db::DefDatabase, path::Path, AdtId, AstItemDef, AttrDefId, HasChildSource, HasSource, Lookup,
+};
+
+#[derive(Default, Debug, Clone, PartialEq, Eq)]
+pub struct Attrs {
+    entries: Option<Arc<[Attr]>>,
+}
+
+impl ops::Deref for Attrs {
+    type Target = [Attr];
+
+    fn deref(&self) -> &[Attr] {
+        match &self.entries {
+            Some(it) => &*it,
+            None => &[],
+        }
+    }
+}
+
+impl Attrs {
+    pub(crate) fn attrs_query(db: &impl DefDatabase, def: AttrDefId) -> Attrs {
+        match def {
+            AttrDefId::ModuleId(module) => {
+                let def_map = db.crate_def_map(module.krate);
+                let src = match def_map[module.module_id].declaration_source(db) {
+                    Some(it) => it,
+                    None => return Attrs::default(),
+                };
+                Attrs::from_attrs_owner(db, src.as_ref().map(|it| it as &dyn AttrsOwner))
+            }
+            AttrDefId::StructFieldId(it) => {
+                let src = it.parent.child_source(db);
+                match &src.value[it.local_id] {
+                    Either::A(_tuple) => Attrs::default(),
+                    Either::B(record) => Attrs::from_attrs_owner(db, src.with_value(record)),
+                }
+            }
+            AttrDefId::EnumVariantId(var_id) => {
+                let src = var_id.parent.child_source(db);
+                let src = src.as_ref().map(|it| &it[var_id.local_id]);
+                Attrs::from_attrs_owner(db, src.map(|it| it as &dyn AttrsOwner))
+            }
+            AttrDefId::AdtId(it) => match it {
+                AdtId::StructId(it) => attrs_from_ast(it.0.lookup_intern(db).ast_id, db),
+                AdtId::EnumId(it) => attrs_from_ast(it.lookup_intern(db).ast_id, db),
+                AdtId::UnionId(it) => attrs_from_ast(it.0.lookup_intern(db).ast_id, db),
+            },
+            AttrDefId::TraitId(it) => attrs_from_ast(it.lookup_intern(db).ast_id, db),
+            AttrDefId::MacroDefId(it) => attrs_from_ast(it.ast_id, db),
+            AttrDefId::ImplId(it) => attrs_from_ast(it.lookup_intern(db).ast_id, db),
+            AttrDefId::ConstId(it) => attrs_from_loc(it.lookup(db), db),
+            AttrDefId::StaticId(it) => attrs_from_loc(it.lookup(db), db),
+            AttrDefId::FunctionId(it) => attrs_from_loc(it.lookup(db), db),
+            AttrDefId::TypeAliasId(it) => attrs_from_loc(it.lookup(db), db),
+        }
+    }
+
+    fn from_attrs_owner(db: &impl DefDatabase, owner: Source<&dyn AttrsOwner>) -> Attrs {
+        let hygiene = Hygiene::new(db, owner.file_id);
+        Attrs::new(owner.value, &hygiene)
+    }
+
+    pub(crate) fn new(owner: &dyn AttrsOwner, hygiene: &Hygiene) -> Attrs {
+        let mut attrs = owner.attrs().peekable();
+        let entries = if attrs.peek().is_none() {
+            // Avoid heap allocation
+            None
+        } else {
+            Some(attrs.flat_map(|ast| Attr::from_src(ast, hygiene)).collect())
+        };
+        Attrs { entries }
+    }
+
+    pub fn by_key(&self, key: &'static str) -> AttrQuery<'_> {
+        AttrQuery { attrs: self, key }
+    }
+}
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Attr {
@@ -26,7 +102,7 @@ pub enum AttrInput {
 }
 
 impl Attr {
-    pub(crate) fn from_src(ast: ast::Attr, hygiene: &Hygiene) -> Option<Attr> {
+    fn from_src(ast: ast::Attr, hygiene: &Hygiene) -> Option<Attr> {
         let path = Path::from_src(ast.path()?, hygiene)?;
         let input = match ast.input() {
             None => None,
@@ -42,43 +118,55 @@ impl Attr {
 
         Some(Attr { path, input })
     }
+}
 
-    pub fn from_attrs_owner(owner: &dyn AttrsOwner, hygiene: &Hygiene) -> Option<Arc<[Attr]>> {
-        let mut attrs = owner.attrs().peekable();
-        if attrs.peek().is_none() {
-            // Avoid heap allocation
-            return None;
-        }
-        Some(attrs.flat_map(|ast| Attr::from_src(ast, hygiene)).collect())
-    }
+pub struct AttrQuery<'a> {
+    attrs: &'a Attrs,
+    key: &'static str,
+}
 
-    pub fn is_simple_atom(&self, name: &str) -> bool {
-        // FIXME: Avoid cloning
-        self.path.as_ident().map_or(false, |s| s.to_string() == name)
+impl<'a> AttrQuery<'a> {
+    pub fn tt_values(self) -> impl Iterator<Item = &'a Subtree> {
+        self.attrs().filter_map(|attr| match attr.input.as_ref()? {
+            AttrInput::TokenTree(it) => Some(it),
+            _ => None,
+        })
     }
 
-    // FIXME: handle cfg_attr :-)
-    pub fn as_cfg(&self) -> Option<&Subtree> {
-        if !self.is_simple_atom("cfg") {
-            return None;
-        }
-        match &self.input {
-            Some(AttrInput::TokenTree(subtree)) => Some(subtree),
+    pub fn string_value(self) -> Option<&'a SmolStr> {
+        self.attrs().find_map(|attr| match attr.input.as_ref()? {
+            AttrInput::Literal(it) => Some(it),
             _ => None,
-        }
+        })
     }
 
-    pub fn as_path(&self) -> Option<&SmolStr> {
-        if !self.is_simple_atom("path") {
-            return None;
-        }
-        match &self.input {
-            Some(AttrInput::Literal(it)) => Some(it),
-            _ => None,
-        }
+    pub fn exists(self) -> bool {
+        self.attrs().next().is_some()
     }
 
-    pub fn is_cfg_enabled(&self, cfg_options: &CfgOptions) -> Option<bool> {
-        cfg_options.is_cfg_enabled(self.as_cfg()?)
+    fn attrs(self) -> impl Iterator<Item = &'a Attr> {
+        let key = self.key;
+        self.attrs
+            .iter()
+            .filter(move |attr| attr.path.as_ident().map_or(false, |s| s.to_string() == key))
     }
 }
+
+fn attrs_from_ast<D, N>(src: AstId<N>, db: &D) -> Attrs
+where
+    N: ast::AttrsOwner,
+    D: DefDatabase,
+{
+    let src = Source::new(src.file_id(), src.to_node(db));
+    Attrs::from_attrs_owner(db, src.as_ref().map(|it| it as &dyn AttrsOwner))
+}
+
+fn attrs_from_loc<T, D>(node: T, db: &D) -> Attrs
+where
+    T: HasSource,
+    T::Value: ast::AttrsOwner,
+    D: DefDatabase,
+{
+    let src = node.source(db);
+    Attrs::from_attrs_owner(db, src.as_ref().map(|it| it as &dyn AttrsOwner))
+}
diff --git a/crates/ra_hir_def/src/body.rs b/crates/ra_hir_def/src/body.rs
index dfb79a30a..d77ccb272 100644
--- a/crates/ra_hir_def/src/body.rs
+++ b/crates/ra_hir_def/src/body.rs
@@ -1,4 +1,5 @@
-//! FIXME: write short doc here
+//! Defines `Body`: a lowered representation of bodies of functions, statics and
+//! consts.
 mod lower;
 pub mod scope;
 
@@ -13,14 +14,14 @@ use ra_syntax::{ast, AstNode, AstPtr};
 use rustc_hash::FxHashMap;
 
 use crate::{
-    db::DefDatabase2,
+    db::DefDatabase,
     expr::{Expr, ExprId, Pat, PatId},
     nameres::CrateDefMap,
     path::Path,
-    AstItemDef, DefWithBodyId, HasModule, HasSource, Lookup, ModuleId,
+    DefWithBodyId, HasModule, HasSource, Lookup, ModuleId,
 };
 
-pub struct Expander {
+struct Expander {
     crate_def_map: Arc<CrateDefMap>,
     current_file_id: HirFileId,
     hygiene: Hygiene,
@@ -28,7 +29,7 @@ pub struct Expander {
 }
 
 impl Expander {
-    pub fn new(db: &impl DefDatabase2, current_file_id: HirFileId, module: ModuleId) -> Expander {
+    fn new(db: &impl DefDatabase, current_file_id: HirFileId, module: ModuleId) -> Expander {
         let crate_def_map = db.crate_def_map(module.krate);
         let hygiene = Hygiene::new(db, current_file_id);
         Expander { crate_def_map, current_file_id, hygiene, module }
@@ -36,7 +37,7 @@ impl Expander {
 
     fn enter_expand(
         &mut self,
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         macro_call: ast::MacroCall,
     ) -> Option<(Mark, ast::Expr)> {
         let ast_id = AstId::new(
@@ -67,7 +68,7 @@ impl Expander {
         None
     }
 
-    fn exit(&mut self, db: &impl DefDatabase2, mark: Mark) {
+    fn exit(&mut self, db: &impl DefDatabase, mark: Mark) {
         self.hygiene = Hygiene::new(db, mark.file_id);
         self.current_file_id = mark.file_id;
         std::mem::forget(mark);
@@ -81,8 +82,8 @@ impl Expander {
         Path::from_src(path, &self.hygiene)
     }
 
-    fn resolve_path_as_macro(&self, db: &impl DefDatabase2, path: &Path) -> Option<MacroDefId> {
-        self.crate_def_map.resolve_path(db, self.module.module_id, path).0.get_macros()
+    fn resolve_path_as_macro(&self, db: &impl DefDatabase, path: &Path) -> Option<MacroDefId> {
+        self.crate_def_map.resolve_path(db, self.module.module_id, path).0.take_macros()
     }
 }
 
@@ -101,17 +102,17 @@ impl Drop for Mark {
 /// The body of an item (function, const etc.).
 #[derive(Debug, Eq, PartialEq)]
 pub struct Body {
-    exprs: Arena<ExprId, Expr>,
-    pats: Arena<PatId, Pat>,
+    pub exprs: Arena<ExprId, Expr>,
+    pub pats: Arena<PatId, Pat>,
     /// The patterns for the function's parameters. While the parameter types are
     /// part of the function signature, the patterns are not (they don't change
     /// the external type of the function).
     ///
     /// If this `Body` is for the body of a constant, this will just be
     /// empty.
-    params: Vec<PatId>,
+    pub params: Vec<PatId>,
     /// The `ExprId` of the actual body expression.
-    body_expr: ExprId,
+    pub body_expr: ExprId,
 }
 
 pub type ExprPtr = Either<AstPtr<ast::Expr>, AstPtr<ast::RecordField>>;
@@ -142,7 +143,7 @@ pub struct BodySourceMap {
 
 impl Body {
     pub(crate) fn body_with_source_map_query(
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         def: DefWithBodyId,
     ) -> (Arc<Body>, Arc<BodySourceMap>) {
         let mut params = None;
@@ -160,6 +161,7 @@ impl Body {
                 (src.file_id, c.module(db), src.value.body())
             }
             DefWithBodyId::StaticId(s) => {
+                let s = s.lookup(db);
                 let src = s.source(db);
                 (src.file_id, s.module(db), src.value.body())
             }
@@ -169,34 +171,18 @@ impl Body {
         (Arc::new(body), Arc::new(source_map))
     }
 
-    pub(crate) fn body_query(db: &impl DefDatabase2, def: DefWithBodyId) -> Arc<Body> {
+    pub(crate) fn body_query(db: &impl DefDatabase, def: DefWithBodyId) -> Arc<Body> {
         db.body_with_source_map(def).0
     }
 
     fn new(
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         expander: Expander,
         params: Option<ast::ParamList>,
         body: Option<ast::Expr>,
     ) -> (Body, BodySourceMap) {
         lower::lower(db, expander, params, body)
     }
-
-    pub fn params(&self) -> &[PatId] {
-        &self.params
-    }
-
-    pub fn body_expr(&self) -> ExprId {
-        self.body_expr
-    }
-
-    pub fn exprs(&self) -> impl Iterator<Item = (ExprId, &Expr)> {
-        self.exprs.iter()
-    }
-
-    pub fn pats(&self) -> impl Iterator<Item = (PatId, &Pat)> {
-        self.pats.iter()
-    }
 }
 
 impl Index<ExprId> for Body {
diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index d8e911aa5..331736cb2 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -1,4 +1,5 @@
-//! FIXME: write short doc here
+//! Transforms `ast::Expr` into an equivalent `hir_def::expr::Expr`
+//! representation.
 
 use hir_expand::{
     either::Either,
@@ -17,7 +18,7 @@ use test_utils::tested_by;
 use crate::{
     body::{Body, BodySourceMap, Expander, PatPtr},
     builtin_type::{BuiltinFloat, BuiltinInt},
-    db::DefDatabase2,
+    db::DefDatabase,
     expr::{
         ArithOp, Array, BinaryOp, BindingAnnotation, CmpOp, Expr, ExprId, Literal, LogicOp,
         MatchArm, Ordering, Pat, PatId, RecordFieldPat, RecordLitField, Statement,
@@ -28,7 +29,7 @@ use crate::{
 };
 
 pub(super) fn lower(
-    db: &impl DefDatabase2,
+    db: &impl DefDatabase,
     expander: Expander,
     params: Option<ast::ParamList>,
     body: Option<ast::Expr>,
@@ -57,7 +58,7 @@ struct ExprCollector<DB> {
 
 impl<'a, DB> ExprCollector<&'a DB>
 where
-    DB: DefDatabase2,
+    DB: DefDatabase,
 {
     fn collect(
         mut self,
diff --git a/crates/ra_hir_def/src/body/scope.rs b/crates/ra_hir_def/src/body/scope.rs
index 58740b679..625aa39dd 100644
--- a/crates/ra_hir_def/src/body/scope.rs
+++ b/crates/ra_hir_def/src/body/scope.rs
@@ -1,4 +1,4 @@
-//! FIXME: write short doc here
+//! Name resolution for expressions.
 use std::sync::Arc;
 
 use hir_expand::name::Name;
@@ -7,7 +7,7 @@ use rustc_hash::FxHashMap;
 
 use crate::{
     body::Body,
-    db::DefDatabase2,
+    db::DefDatabase,
     expr::{Expr, ExprId, Pat, PatId, Statement},
     DefWithBodyId,
 };
@@ -45,7 +45,7 @@ pub struct ScopeData {
 }
 
 impl ExprScopes {
-    pub(crate) fn expr_scopes_query(db: &impl DefDatabase2, def: DefWithBodyId) -> Arc<ExprScopes> {
+    pub(crate) fn expr_scopes_query(db: &impl DefDatabase, def: DefWithBodyId) -> Arc<ExprScopes> {
         let body = db.body(def);
         Arc::new(ExprScopes::new(&*body))
     }
@@ -54,8 +54,8 @@ impl ExprScopes {
         let mut scopes =
             ExprScopes { scopes: Arena::default(), scope_by_expr: FxHashMap::default() };
         let root = scopes.root_scope();
-        scopes.add_params_bindings(body, root, body.params());
-        compute_expr_scopes(body.body_expr(), body, &mut scopes, root);
+        scopes.add_params_bindings(body, root, &body.params);
+        compute_expr_scopes(body.body_expr, body, &mut scopes, root);
         scopes
     }
 
@@ -176,7 +176,7 @@ mod tests {
     use ra_syntax::{algo::find_node_at_offset, ast, AstNode};
     use test_utils::{assert_eq_text, covers, extract_offset};
 
-    use crate::{db::DefDatabase2, test_db::TestDB, FunctionId, ModuleDefId};
+    use crate::{db::DefDatabase, test_db::TestDB, FunctionId, ModuleDefId};
 
     fn find_function(db: &TestDB, file_id: FileId) -> FunctionId {
         let krate = db.test_crate();
diff --git a/crates/ra_hir_def/src/data.rs b/crates/ra_hir_def/src/data.rs
new file mode 100644
index 000000000..68bea34df
--- /dev/null
+++ b/crates/ra_hir_def/src/data.rs
@@ -0,0 +1,216 @@
+//! Contains basic data about various HIR declarations.
+
+use std::sync::Arc;
+
+use hir_expand::{
+    name::{self, AsName, Name},
+    AstId,
+};
+use ra_syntax::ast::{self, NameOwner, TypeAscriptionOwner};
+
+use crate::{
+    db::DefDatabase,
+    type_ref::{Mutability, TypeRef},
+    AssocItemId, AstItemDef, ConstId, ConstLoc, ContainerId, FunctionId, FunctionLoc, HasSource,
+    ImplId, Intern, Lookup, StaticId, TraitId, TypeAliasId, TypeAliasLoc,
+};
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct FunctionData {
+    pub name: Name,
+    pub params: Vec<TypeRef>,
+    pub ret_type: TypeRef,
+    /// True if the first param is `self`. This is relevant to decide whether this
+    /// can be called as a method.
+    pub has_self_param: bool,
+}
+
+impl FunctionData {
+    pub(crate) fn fn_data_query(db: &impl DefDatabase, func: FunctionId) -> Arc<FunctionData> {
+        let src = func.lookup(db).source(db);
+        let name = src.value.name().map(|n| n.as_name()).unwrap_or_else(Name::missing);
+        let mut params = Vec::new();
+        let mut has_self_param = false;
+        if let Some(param_list) = src.value.param_list() {
+            if let Some(self_param) = param_list.self_param() {
+                let self_type = if let Some(type_ref) = self_param.ascribed_type() {
+                    TypeRef::from_ast(type_ref)
+                } else {
+                    let self_type = TypeRef::Path(name::SELF_TYPE.into());
+                    match self_param.kind() {
+                        ast::SelfParamKind::Owned => self_type,
+                        ast::SelfParamKind::Ref => {
+                            TypeRef::Reference(Box::new(self_type), Mutability::Shared)
+                        }
+                        ast::SelfParamKind::MutRef => {
+                            TypeRef::Reference(Box::new(self_type), Mutability::Mut)
+                        }
+                    }
+                };
+                params.push(self_type);
+                has_self_param = true;
+            }
+            for param in param_list.params() {
+                let type_ref = TypeRef::from_ast_opt(param.ascribed_type());
+                params.push(type_ref);
+            }
+        }
+        let ret_type = if let Some(type_ref) = src.value.ret_type().and_then(|rt| rt.type_ref()) {
+            TypeRef::from_ast(type_ref)
+        } else {
+            TypeRef::unit()
+        };
+
+        let sig = FunctionData { name, params, ret_type, has_self_param };
+        Arc::new(sig)
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct TypeAliasData {
+    pub name: Name,
+    pub type_ref: Option<TypeRef>,
+}
+
+impl TypeAliasData {
+    pub(crate) fn type_alias_data_query(
+        db: &impl DefDatabase,
+        typ: TypeAliasId,
+    ) -> Arc<TypeAliasData> {
+        let node = typ.lookup(db).source(db).value;
+        let name = node.name().map_or_else(Name::missing, |n| n.as_name());
+        let type_ref = node.type_ref().map(TypeRef::from_ast);
+        Arc::new(TypeAliasData { name, type_ref })
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct TraitData {
+    pub name: Option<Name>,
+    pub items: Vec<AssocItemId>,
+    pub auto: bool,
+}
+
+impl TraitData {
+    pub(crate) fn trait_data_query(db: &impl DefDatabase, tr: TraitId) -> Arc<TraitData> {
+        let src = tr.source(db);
+        let name = src.value.name().map(|n| n.as_name());
+        let auto = src.value.is_auto();
+        let ast_id_map = db.ast_id_map(src.file_id);
+        let items = if let Some(item_list) = src.value.item_list() {
+            item_list
+                .impl_items()
+                .map(|item_node| match item_node {
+                    ast::ImplItem::FnDef(it) => FunctionLoc {
+                        container: ContainerId::TraitId(tr),
+                        ast_id: AstId::new(src.file_id, ast_id_map.ast_id(&it)),
+                    }
+                    .intern(db)
+                    .into(),
+                    ast::ImplItem::ConstDef(it) => ConstLoc {
+                        container: ContainerId::TraitId(tr),
+                        ast_id: AstId::new(src.file_id, ast_id_map.ast_id(&it)),
+                    }
+                    .intern(db)
+                    .into(),
+                    ast::ImplItem::TypeAliasDef(it) => TypeAliasLoc {
+                        container: ContainerId::TraitId(tr),
+                        ast_id: AstId::new(src.file_id, ast_id_map.ast_id(&it)),
+                    }
+                    .intern(db)
+                    .into(),
+                })
+                .collect()
+        } else {
+            Vec::new()
+        };
+        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,
+        })
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ImplData {
+    pub target_trait: Option<TypeRef>,
+    pub target_type: TypeRef,
+    pub items: Vec<AssocItemId>,
+    pub is_negative: bool,
+}
+
+impl ImplData {
+    pub(crate) fn impl_data_query(db: &impl DefDatabase, id: ImplId) -> Arc<ImplData> {
+        let src = id.source(db);
+        let items = db.ast_id_map(src.file_id);
+
+        let target_trait = src.value.target_trait().map(TypeRef::from_ast);
+        let target_type = TypeRef::from_ast_opt(src.value.target_type());
+        let is_negative = src.value.is_negative();
+
+        let items = if let Some(item_list) = src.value.item_list() {
+            item_list
+                .impl_items()
+                .map(|item_node| match item_node {
+                    ast::ImplItem::FnDef(it) => {
+                        let def = FunctionLoc {
+                            container: ContainerId::ImplId(id),
+                            ast_id: AstId::new(src.file_id, items.ast_id(&it)),
+                        }
+                        .intern(db);
+                        def.into()
+                    }
+                    ast::ImplItem::ConstDef(it) => {
+                        let def = ConstLoc {
+                            container: ContainerId::ImplId(id),
+                            ast_id: AstId::new(src.file_id, items.ast_id(&it)),
+                        }
+                        .intern(db);
+                        def.into()
+                    }
+                    ast::ImplItem::TypeAliasDef(it) => {
+                        let def = TypeAliasLoc {
+                            container: ContainerId::ImplId(id),
+                            ast_id: AstId::new(src.file_id, items.ast_id(&it)),
+                        }
+                        .intern(db);
+                        def.into()
+                    }
+                })
+                .collect()
+        } else {
+            Vec::new()
+        };
+
+        let res = ImplData { target_trait, target_type, items, is_negative };
+        Arc::new(res)
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ConstData {
+    pub name: Option<Name>,
+    pub type_ref: TypeRef,
+}
+
+impl ConstData {
+    pub(crate) fn const_data_query(db: &impl DefDatabase, konst: ConstId) -> Arc<ConstData> {
+        let node = konst.lookup(db).source(db).value;
+        Arc::new(ConstData::new(&node))
+    }
+
+    pub(crate) fn static_data_query(db: &impl DefDatabase, konst: StaticId) -> Arc<ConstData> {
+        let node = konst.lookup(db).source(db).value;
+        Arc::new(ConstData::new(&node))
+    }
+
+    fn new<N: NameOwner + TypeAscriptionOwner>(node: &N) -> ConstData {
+        let name = node.name().map(|n| n.as_name());
+        let type_ref = TypeRef::from_ast_opt(node.ascribed_type());
+        ConstData { name, type_ref }
+    }
+}
diff --git a/crates/ra_hir_def/src/db.rs b/crates/ra_hir_def/src/db.rs
index 844f8bbe8..32adb11bd 100644
--- a/crates/ra_hir_def/src/db.rs
+++ b/crates/ra_hir_def/src/db.rs
@@ -3,43 +3,47 @@ use std::sync::Arc;
 
 use hir_expand::{db::AstDatabase, HirFileId};
 use ra_db::{salsa, CrateId, SourceDatabase};
-use ra_syntax::ast;
+use ra_syntax::{ast, SmolStr};
 
 use crate::{
     adt::{EnumData, StructData},
+    attr::Attrs,
     body::{scope::ExprScopes, Body, BodySourceMap},
+    data::{ConstData, FunctionData, ImplData, TraitData, TypeAliasData},
+    docs::Documentation,
     generics::GenericParams,
-    impls::ImplData,
+    lang_item::{LangItemTarget, LangItems},
     nameres::{
         raw::{ImportSourceMap, RawItems},
         CrateDefMap,
     },
-    traits::TraitData,
-    DefWithBodyId, EnumId, GenericDefId, ImplId, ItemLoc, StructOrUnionId, TraitId,
+    AttrDefId, ConstId, ConstLoc, DefWithBodyId, EnumId, FunctionId, FunctionLoc, GenericDefId,
+    ImplId, ItemLoc, ModuleId, StaticId, StaticLoc, StructOrUnionId, TraitId, TypeAliasId,
+    TypeAliasLoc,
 };
 
 #[salsa::query_group(InternDatabaseStorage)]
 pub trait InternDatabase: SourceDatabase {
     #[salsa::interned]
-    fn intern_function(&self, loc: crate::FunctionLoc) -> crate::FunctionId;
+    fn intern_function(&self, loc: FunctionLoc) -> FunctionId;
     #[salsa::interned]
-    fn intern_struct_or_union(&self, loc: ItemLoc<ast::StructDef>) -> crate::StructOrUnionId;
+    fn intern_struct_or_union(&self, loc: ItemLoc<ast::StructDef>) -> StructOrUnionId;
     #[salsa::interned]
-    fn intern_enum(&self, loc: ItemLoc<ast::EnumDef>) -> crate::EnumId;
+    fn intern_enum(&self, loc: ItemLoc<ast::EnumDef>) -> EnumId;
     #[salsa::interned]
-    fn intern_const(&self, loc: crate::ConstLoc) -> crate::ConstId;
+    fn intern_const(&self, loc: ConstLoc) -> ConstId;
     #[salsa::interned]
-    fn intern_static(&self, loc: ItemLoc<ast::StaticDef>) -> crate::StaticId;
+    fn intern_static(&self, loc: StaticLoc) -> StaticId;
     #[salsa::interned]
-    fn intern_trait(&self, loc: ItemLoc<ast::TraitDef>) -> crate::TraitId;
+    fn intern_trait(&self, loc: ItemLoc<ast::TraitDef>) -> TraitId;
     #[salsa::interned]
-    fn intern_type_alias(&self, loc: crate::TypeAliasLoc) -> crate::TypeAliasId;
+    fn intern_type_alias(&self, loc: TypeAliasLoc) -> TypeAliasId;
     #[salsa::interned]
-    fn intern_impl(&self, loc: ItemLoc<ast::ImplBlock>) -> crate::ImplId;
+    fn intern_impl(&self, loc: ItemLoc<ast::ImplBlock>) -> ImplId;
 }
 
-#[salsa::query_group(DefDatabase2Storage)]
-pub trait DefDatabase2: InternDatabase + AstDatabase {
+#[salsa::query_group(DefDatabaseStorage)]
+pub trait DefDatabase: InternDatabase + AstDatabase {
     #[salsa::invoke(RawItems::raw_items_with_source_map_query)]
     fn raw_items_with_source_map(
         &self,
@@ -64,6 +68,18 @@ pub trait DefDatabase2: InternDatabase + AstDatabase {
     #[salsa::invoke(TraitData::trait_data_query)]
     fn trait_data(&self, e: TraitId) -> Arc<TraitData>;
 
+    #[salsa::invoke(TypeAliasData::type_alias_data_query)]
+    fn type_alias_data(&self, e: TypeAliasId) -> Arc<TypeAliasData>;
+
+    #[salsa::invoke(FunctionData::fn_data_query)]
+    fn function_data(&self, func: FunctionId) -> Arc<FunctionData>;
+
+    #[salsa::invoke(ConstData::const_data_query)]
+    fn const_data(&self, konst: ConstId) -> Arc<ConstData>;
+
+    #[salsa::invoke(ConstData::static_data_query)]
+    fn static_data(&self, konst: StaticId) -> Arc<ConstData>;
+
     #[salsa::invoke(Body::body_with_source_map_query)]
     fn body_with_source_map(&self, def: DefWithBodyId) -> (Arc<Body>, Arc<BodySourceMap>);
 
@@ -75,4 +91,21 @@ pub trait DefDatabase2: InternDatabase + AstDatabase {
 
     #[salsa::invoke(GenericParams::generic_params_query)]
     fn generic_params(&self, def: GenericDefId) -> Arc<GenericParams>;
+
+    #[salsa::invoke(Attrs::attrs_query)]
+    fn attrs(&self, def: AttrDefId) -> Attrs;
+
+    #[salsa::invoke(LangItems::module_lang_items_query)]
+    fn module_lang_items(&self, module: ModuleId) -> Option<Arc<LangItems>>;
+
+    #[salsa::invoke(LangItems::crate_lang_items_query)]
+    fn crate_lang_items(&self, krate: CrateId) -> Arc<LangItems>;
+
+    #[salsa::invoke(LangItems::lang_item_query)]
+    fn lang_item(&self, start_crate: CrateId, item: SmolStr) -> Option<LangItemTarget>;
+
+    // FIXME(https://github.com/rust-analyzer/rust-analyzer/issues/2148#issuecomment-550519102)
+    // Remove this query completely, in favor of `Attrs::docs` method
+    #[salsa::invoke(Documentation::documentation_query)]
+    fn documentation(&self, def: AttrDefId) -> Option<Documentation>;
 }
diff --git a/crates/ra_hir_def/src/docs.rs b/crates/ra_hir_def/src/docs.rs
new file mode 100644
index 000000000..90a8627bc
--- /dev/null
+++ b/crates/ra_hir_def/src/docs.rs
@@ -0,0 +1,71 @@
+//! Defines hir documentation.
+//!
+//! This really shouldn't exist, instead, we should deshugar doc comments into attributes, see
+//! https://github.com/rust-analyzer/rust-analyzer/issues/2148#issuecomment-550519102
+
+use std::sync::Arc;
+
+use hir_expand::either::Either;
+use ra_syntax::ast;
+
+use crate::{db::DefDatabase, AdtId, AstItemDef, AttrDefId, HasChildSource, HasSource, Lookup};
+
+/// Holds documentation
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Documentation(Arc<str>);
+
+impl Into<String> for Documentation {
+    fn into(self) -> String {
+        self.as_str().to_owned()
+    }
+}
+
+impl Documentation {
+    fn new(s: &str) -> Documentation {
+        Documentation(s.into())
+    }
+
+    pub fn as_str(&self) -> &str {
+        &*self.0
+    }
+
+    pub(crate) fn documentation_query(
+        db: &impl DefDatabase,
+        def: AttrDefId,
+    ) -> Option<Documentation> {
+        match def {
+            AttrDefId::ModuleId(module) => {
+                let def_map = db.crate_def_map(module.krate);
+                let src = def_map[module.module_id].declaration_source(db)?;
+                docs_from_ast(&src.value)
+            }
+            AttrDefId::StructFieldId(it) => {
+                let src = it.parent.child_source(db);
+                match &src.value[it.local_id] {
+                    Either::A(_tuple) => None,
+                    Either::B(record) => docs_from_ast(record),
+                }
+            }
+            AttrDefId::AdtId(it) => match it {
+                AdtId::StructId(it) => docs_from_ast(&it.0.source(db).value),
+                AdtId::EnumId(it) => docs_from_ast(&it.source(db).value),
+                AdtId::UnionId(it) => docs_from_ast(&it.0.source(db).value),
+            },
+            AttrDefId::EnumVariantId(it) => {
+                let src = it.parent.child_source(db);
+                docs_from_ast(&src.value[it.local_id])
+            }
+            AttrDefId::TraitId(it) => docs_from_ast(&it.source(db).value),
+            AttrDefId::MacroDefId(it) => docs_from_ast(&it.ast_id.to_node(db)),
+            AttrDefId::ConstId(it) => docs_from_ast(&it.lookup(db).source(db).value),
+            AttrDefId::StaticId(it) => docs_from_ast(&it.lookup(db).source(db).value),
+            AttrDefId::FunctionId(it) => docs_from_ast(&it.lookup(db).source(db).value),
+            AttrDefId::TypeAliasId(it) => docs_from_ast(&it.lookup(db).source(db).value),
+            AttrDefId::ImplId(_) => None,
+        }
+    }
+}
+
+pub(crate) fn docs_from_ast(node: &impl ast::DocCommentsOwner) -> Option<Documentation> {
+    node.doc_comment_text().map(|it| Documentation::new(&it))
+}
diff --git a/crates/ra_hir_def/src/generics.rs b/crates/ra_hir_def/src/generics.rs
index 9e2e4c3cc..015fe772e 100644
--- a/crates/ra_hir_def/src/generics.rs
+++ b/crates/ra_hir_def/src/generics.rs
@@ -8,7 +8,7 @@ use hir_expand::name::{self, AsName, Name};
 use ra_syntax::ast::{self, NameOwner, TypeBoundsOwner, TypeParamsOwner};
 
 use crate::{
-    db::DefDatabase2,
+    db::DefDatabase,
     type_ref::{TypeBound, TypeRef},
     AdtId, AstItemDef, ContainerId, GenericDefId, HasSource, Lookup,
 };
@@ -42,7 +42,7 @@ pub struct WherePredicate {
 
 impl GenericParams {
     pub(crate) fn generic_params_query(
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         def: GenericDefId,
     ) -> Arc<GenericParams> {
         let parent_generics = parent_generic_def(db, def).map(|it| db.generic_params(it));
@@ -50,7 +50,7 @@ impl GenericParams {
     }
 
     fn new(
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         def: GenericDefId,
         parent_params: Option<Arc<GenericParams>>,
     ) -> GenericParams {
@@ -168,7 +168,7 @@ impl GenericParams {
     }
 }
 
-fn parent_generic_def(db: &impl DefDatabase2, def: GenericDefId) -> Option<GenericDefId> {
+fn parent_generic_def(db: &impl DefDatabase, def: GenericDefId) -> Option<GenericDefId> {
     let container = match def {
         GenericDefId::FunctionId(it) => it.lookup(db).container,
         GenericDefId::TypeAliasId(it) => it.lookup(db).container,
diff --git a/crates/ra_hir_def/src/impls.rs b/crates/ra_hir_def/src/impls.rs
deleted file mode 100644
index 750a869f2..000000000
--- a/crates/ra_hir_def/src/impls.rs
+++ /dev/null
@@ -1,86 +0,0 @@
-//! Defines hir-level representation of impls.
-//!
-//! The handling is similar, but is not quite the same as for other items,
-//! because `impl`s don't have names.
-
-use std::sync::Arc;
-
-use hir_expand::AstId;
-use ra_syntax::ast;
-
-use crate::{
-    db::DefDatabase2, type_ref::TypeRef, AssocItemId, AstItemDef, ConstLoc, ContainerId,
-    FunctionLoc, ImplId, Intern, TypeAliasLoc,
-};
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct ImplData {
-    target_trait: Option<TypeRef>,
-    target_type: TypeRef,
-    items: Vec<AssocItemId>,
-    negative: bool,
-}
-
-impl ImplData {
-    pub(crate) fn impl_data_query(db: &impl DefDatabase2, id: ImplId) -> Arc<ImplData> {
-        let src = id.source(db);
-        let items = db.ast_id_map(src.file_id);
-
-        let target_trait = src.value.target_trait().map(TypeRef::from_ast);
-        let target_type = TypeRef::from_ast_opt(src.value.target_type());
-        let negative = src.value.is_negative();
-
-        let items = if let Some(item_list) = src.value.item_list() {
-            item_list
-                .impl_items()
-                .map(|item_node| match item_node {
-                    ast::ImplItem::FnDef(it) => {
-                        let def = FunctionLoc {
-                            container: ContainerId::ImplId(id),
-                            ast_id: AstId::new(src.file_id, items.ast_id(&it)),
-                        }
-                        .intern(db);
-                        def.into()
-                    }
-                    ast::ImplItem::ConstDef(it) => {
-                        let def = ConstLoc {
-                            container: ContainerId::ImplId(id),
-                            ast_id: AstId::new(src.file_id, items.ast_id(&it)),
-                        }
-                        .intern(db);
-                        def.into()
-                    }
-                    ast::ImplItem::TypeAliasDef(it) => {
-                        let def = TypeAliasLoc {
-                            container: ContainerId::ImplId(id),
-                            ast_id: AstId::new(src.file_id, items.ast_id(&it)),
-                        }
-                        .intern(db);
-                        def.into()
-                    }
-                })
-                .collect()
-        } else {
-            Vec::new()
-        };
-
-        let res = ImplData { target_trait, target_type, items, negative };
-        Arc::new(res)
-    }
-
-    pub fn target_trait(&self) -> Option<&TypeRef> {
-        self.target_trait.as_ref()
-    }
-
-    pub fn target_type(&self) -> &TypeRef {
-        &self.target_type
-    }
-
-    pub fn items(&self) -> &[AssocItemId] {
-        &self.items
-    }
-
-    pub fn is_negative(&self) -> bool {
-        self.negative
-    }
-}
diff --git a/crates/ra_hir_def/src/lang_item.rs b/crates/ra_hir_def/src/lang_item.rs
new file mode 100644
index 000000000..f15c23db9
--- /dev/null
+++ b/crates/ra_hir_def/src/lang_item.rs
@@ -0,0 +1,121 @@
+//! Collects lang items: items marked with `#[lang = "..."]` attribute.
+//!
+//! This attribute to tell the compiler about semi built-in std library
+//! features, such as Fn family of traits.
+use std::sync::Arc;
+
+use ra_syntax::SmolStr;
+use rustc_hash::FxHashMap;
+
+use crate::{
+    db::DefDatabase, AdtId, AttrDefId, CrateId, EnumId, FunctionId, ImplId, ModuleDefId, ModuleId,
+    StaticId, StructId, TraitId,
+};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum LangItemTarget {
+    EnumId(EnumId),
+    FunctionId(FunctionId),
+    ImplBlockId(ImplId),
+    StaticId(StaticId),
+    StructId(StructId),
+    TraitId(TraitId),
+}
+
+#[derive(Default, Debug, Clone, PartialEq, Eq)]
+pub struct LangItems {
+    items: FxHashMap<SmolStr, LangItemTarget>,
+}
+
+impl LangItems {
+    pub fn target<'a>(&'a self, item: &str) -> Option<&'a LangItemTarget> {
+        self.items.get(item)
+    }
+
+    /// Salsa query. This will look for lang items in a specific crate.
+    pub(crate) fn crate_lang_items_query(db: &impl DefDatabase, krate: CrateId) -> Arc<LangItems> {
+        let mut lang_items = LangItems::default();
+
+        let crate_def_map = db.crate_def_map(krate);
+
+        crate_def_map
+            .modules
+            .iter()
+            .filter_map(|(module_id, _)| db.module_lang_items(ModuleId { krate, module_id }))
+            .for_each(|it| lang_items.items.extend(it.items.iter().map(|(k, v)| (k.clone(), *v))));
+
+        Arc::new(lang_items)
+    }
+
+    pub(crate) fn module_lang_items_query(
+        db: &impl DefDatabase,
+        module: ModuleId,
+    ) -> Option<Arc<LangItems>> {
+        let mut lang_items = LangItems::default();
+        lang_items.collect_lang_items(db, module);
+        if lang_items.items.is_empty() {
+            None
+        } else {
+            Some(Arc::new(lang_items))
+        }
+    }
+
+    /// Salsa query. Look for a lang item, starting from the specified crate and recursively
+    /// traversing its dependencies.
+    pub(crate) fn lang_item_query(
+        db: &impl DefDatabase,
+        start_crate: CrateId,
+        item: SmolStr,
+    ) -> Option<LangItemTarget> {
+        let lang_items = db.crate_lang_items(start_crate);
+        let start_crate_target = lang_items.items.get(&item);
+        if let Some(target) = start_crate_target {
+            return Some(*target);
+        }
+        db.crate_graph()
+            .dependencies(start_crate)
+            .find_map(|dep| db.lang_item(dep.crate_id, item.clone()))
+    }
+
+    fn collect_lang_items(&mut self, db: &impl DefDatabase, module: ModuleId) {
+        // Look for impl targets
+        let def_map = db.crate_def_map(module.krate);
+        let module_data = &def_map[module.module_id];
+        for &impl_block in module_data.impls.iter() {
+            self.collect_lang_item(db, impl_block, LangItemTarget::ImplBlockId)
+        }
+
+        for def in module_data.scope.declarations() {
+            match def {
+                ModuleDefId::TraitId(trait_) => {
+                    self.collect_lang_item(db, trait_, LangItemTarget::TraitId)
+                }
+                ModuleDefId::AdtId(AdtId::EnumId(e)) => {
+                    self.collect_lang_item(db, e, LangItemTarget::EnumId)
+                }
+                ModuleDefId::AdtId(AdtId::StructId(s)) => {
+                    self.collect_lang_item(db, s, LangItemTarget::StructId)
+                }
+                ModuleDefId::FunctionId(f) => {
+                    self.collect_lang_item(db, f, LangItemTarget::FunctionId)
+                }
+                ModuleDefId::StaticId(s) => self.collect_lang_item(db, s, LangItemTarget::StaticId),
+                _ => {}
+            }
+        }
+    }
+
+    fn collect_lang_item<T>(
+        &mut self,
+        db: &impl DefDatabase,
+        item: T,
+        constructor: fn(T) -> LangItemTarget,
+    ) where
+        T: Into<AttrDefId> + Copy,
+    {
+        let attrs = db.attrs(item.into());
+        if let Some(lang_item_name) = attrs.by_key("lang").string_value() {
+            self.items.entry(lang_item_name.clone()).or_insert_with(|| constructor(item));
+        }
+    }
+}
diff --git a/crates/ra_hir_def/src/lib.rs b/crates/ra_hir_def/src/lib.rs
index d579f5c7e..8e8c2d749 100644
--- a/crates/ra_hir_def/src/lib.rs
+++ b/crates/ra_hir_def/src/lib.rs
@@ -8,121 +8,56 @@
 //! actually true.
 
 pub mod db;
+
 pub mod attr;
 pub mod path;
 pub mod type_ref;
 pub mod builtin_type;
-pub mod adt;
-pub mod impls;
 pub mod diagnostics;
+pub mod per_ns;
+
+pub mod adt;
+pub mod data;
+pub mod generics;
+pub mod lang_item;
+pub mod docs;
+
 pub mod expr;
 pub mod body;
-pub mod generics;
-pub mod traits;
 pub mod resolver;
 
+mod trace;
+mod nameres;
+
 #[cfg(test)]
 mod test_db;
 #[cfg(test)]
 mod marks;
 
-// FIXME: this should be private
-pub mod nameres;
-
 use std::hash::{Hash, Hasher};
 
-use hir_expand::{ast_id_map::FileAstId, db::AstDatabase, AstId, HirFileId, Source};
-use ra_arena::{impl_arena_id, RawId};
-use ra_db::{salsa, CrateId, FileId};
-use ra_syntax::{ast, AstNode, SyntaxNode};
+use hir_expand::{ast_id_map::FileAstId, db::AstDatabase, AstId, HirFileId, MacroDefId, Source};
+use ra_arena::{impl_arena_id, map::ArenaMap, RawId};
+use ra_db::{impl_intern_key, salsa, CrateId};
+use ra_syntax::{ast, AstNode};
 
 use crate::{builtin_type::BuiltinType, db::InternDatabase};
 
-pub enum ModuleSource {
-    SourceFile(ast::SourceFile),
-    Module(ast::Module),
-}
-
-impl ModuleSource {
-    pub fn new(
-        db: &impl db::DefDatabase2,
-        file_id: Option<FileId>,
-        decl_id: Option<AstId<ast::Module>>,
-    ) -> ModuleSource {
-        match (file_id, decl_id) {
-            (Some(file_id), _) => {
-                let source_file = db.parse(file_id).tree();
-                ModuleSource::SourceFile(source_file)
-            }
-            (None, Some(item_id)) => {
-                let module = item_id.to_node(db);
-                assert!(module.item_list().is_some(), "expected inline module");
-                ModuleSource::Module(module)
-            }
-            (None, None) => panic!(),
-        }
-    }
-
-    // FIXME: this methods do not belong here
-    pub fn from_position(
-        db: &impl db::DefDatabase2,
-        position: ra_db::FilePosition,
-    ) -> ModuleSource {
-        let parse = db.parse(position.file_id);
-        match &ra_syntax::algo::find_node_at_offset::<ast::Module>(
-            parse.tree().syntax(),
-            position.offset,
-        ) {
-            Some(m) if !m.has_semi() => ModuleSource::Module(m.clone()),
-            _ => {
-                let source_file = parse.tree();
-                ModuleSource::SourceFile(source_file)
-            }
-        }
-    }
-
-    pub fn from_child_node(db: &impl db::DefDatabase2, child: Source<&SyntaxNode>) -> ModuleSource {
-        if let Some(m) =
-            child.value.ancestors().filter_map(ast::Module::cast).find(|it| !it.has_semi())
-        {
-            ModuleSource::Module(m)
-        } else {
-            let file_id = child.file_id.original_file(db);
-            let source_file = db.parse(file_id).tree();
-            ModuleSource::SourceFile(source_file)
-        }
-    }
-
-    pub fn from_file_id(db: &impl db::DefDatabase2, file_id: FileId) -> ModuleSource {
-        let source_file = db.parse(file_id).tree();
-        ModuleSource::SourceFile(source_file)
-    }
-}
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct LocalImportId(RawId);
+impl_arena_id!(LocalImportId);
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct ModuleId {
     pub krate: CrateId,
-    pub module_id: CrateModuleId,
+    pub module_id: LocalModuleId,
 }
 
 /// An ID of a module, **local** to a specific crate
 // FIXME: rename to `LocalModuleId`.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct CrateModuleId(RawId);
-impl_arena_id!(CrateModuleId);
-
-macro_rules! impl_intern_key {
-    ($name:ident) => {
-        impl salsa::InternKey for $name {
-            fn from_intern_id(v: salsa::InternId) -> Self {
-                $name(v)
-            }
-            fn as_intern_id(&self) -> salsa::InternId {
-                self.0
-            }
-        }
-    };
-}
+pub struct LocalModuleId(RawId);
+impl_arena_id!(LocalModuleId);
 
 #[derive(Debug)]
 pub struct ItemLoc<N: AstNode> {
@@ -162,25 +97,10 @@ impl<'a, DB> LocationCtx<&'a DB> {
     }
 }
 
-impl<'a, DB: AstDatabase + InternDatabase> LocationCtx<&'a DB> {
-    pub fn to_def<N, DEF>(self, ast: &N) -> DEF
-    where
-        N: AstNode,
-        DEF: AstItemDef<N>,
-    {
-        DEF::from_ast(self, ast)
-    }
-}
-
 pub trait AstItemDef<N: AstNode>: salsa::InternKey + Clone {
     fn intern(db: &impl InternDatabase, loc: ItemLoc<N>) -> Self;
     fn lookup_intern(self, db: &impl InternDatabase) -> ItemLoc<N>;
 
-    fn from_ast(ctx: LocationCtx<&(impl AstDatabase + InternDatabase)>, ast: &N) -> Self {
-        let items = ctx.db.ast_id_map(ctx.file_id);
-        let item_id = items.ast_id(ast);
-        Self::from_ast_id(ctx, item_id)
-    }
     fn from_ast_id(ctx: LocationCtx<&impl InternDatabase>, ast_id: FileAstId<N>) -> Self {
         let loc = ItemLoc { module: ctx.module, ast_id: AstId::new(ctx.file_id, ast_id) };
         Self::intern(ctx.db, loc)
@@ -208,14 +128,14 @@ pub struct FunctionLoc {
 
 impl Intern for FunctionLoc {
     type ID = FunctionId;
-    fn intern(self, db: &impl db::DefDatabase2) -> FunctionId {
+    fn intern(self, db: &impl db::DefDatabase) -> FunctionId {
         db.intern_function(self)
     }
 }
 
 impl Lookup for FunctionId {
     type Data = FunctionLoc;
-    fn lookup(&self, db: &impl db::DefDatabase2) -> FunctionLoc {
+    fn lookup(&self, db: &impl db::DefDatabase) -> FunctionLoc {
         db.lookup_intern_function(*self)
     }
 }
@@ -272,15 +192,9 @@ pub struct LocalEnumVariantId(RawId);
 impl_arena_id!(LocalEnumVariantId);
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub enum VariantId {
-    EnumVariantId(EnumVariantId),
-    StructId(StructId),
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct StructFieldId {
-    parent: VariantId,
-    local_id: LocalStructFieldId,
+    pub parent: VariantId,
+    pub local_id: LocalStructFieldId,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
@@ -298,14 +212,14 @@ pub struct ConstLoc {
 
 impl Intern for ConstLoc {
     type ID = ConstId;
-    fn intern(self, db: &impl db::DefDatabase2) -> ConstId {
+    fn intern(self, db: &impl db::DefDatabase) -> ConstId {
         db.intern_const(self)
     }
 }
 
 impl Lookup for ConstId {
     type Data = ConstLoc;
-    fn lookup(&self, db: &impl db::DefDatabase2) -> ConstLoc {
+    fn lookup(&self, db: &impl db::DefDatabase) -> ConstLoc {
         db.lookup_intern_const(*self)
     }
 }
@@ -313,12 +227,24 @@ impl Lookup for ConstId {
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct StaticId(salsa::InternId);
 impl_intern_key!(StaticId);
-impl AstItemDef<ast::StaticDef> for StaticId {
-    fn intern(db: &impl InternDatabase, loc: ItemLoc<ast::StaticDef>) -> Self {
-        db.intern_static(loc)
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct StaticLoc {
+    pub container: ModuleId,
+    pub ast_id: AstId<ast::StaticDef>,
+}
+
+impl Intern for StaticLoc {
+    type ID = StaticId;
+    fn intern(self, db: &impl db::DefDatabase) -> StaticId {
+        db.intern_static(self)
     }
-    fn lookup_intern(self, db: &impl InternDatabase) -> ItemLoc<ast::StaticDef> {
-        db.lookup_intern_static(self)
+}
+
+impl Lookup for StaticId {
+    type Data = StaticLoc;
+    fn lookup(&self, db: &impl db::DefDatabase) -> StaticLoc {
+        db.lookup_intern_static(*self)
     }
 }
 
@@ -346,14 +272,14 @@ pub struct TypeAliasLoc {
 
 impl Intern for TypeAliasLoc {
     type ID = TypeAliasId;
-    fn intern(self, db: &impl db::DefDatabase2) -> TypeAliasId {
+    fn intern(self, db: &impl db::DefDatabase) -> TypeAliasId {
         db.intern_type_alias(self)
     }
 }
 
 impl Lookup for TypeAliasId {
     type Data = TypeAliasLoc;
-    fn lookup(&self, db: &impl db::DefDatabase2) -> TypeAliasLoc {
+    fn lookup(&self, db: &impl db::DefDatabase) -> TypeAliasLoc {
         db.lookup_intern_type_alias(*self)
     }
 }
@@ -476,22 +402,58 @@ impl_froms!(
     ConstId
 );
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum AttrDefId {
+    ModuleId(ModuleId),
+    StructFieldId(StructFieldId),
+    AdtId(AdtId),
+    FunctionId(FunctionId),
+    EnumVariantId(EnumVariantId),
+    StaticId(StaticId),
+    ConstId(ConstId),
+    TraitId(TraitId),
+    TypeAliasId(TypeAliasId),
+    MacroDefId(MacroDefId),
+    ImplId(ImplId),
+}
+
+impl_froms!(
+    AttrDefId: ModuleId,
+    StructFieldId,
+    AdtId(StructId, EnumId, UnionId),
+    EnumVariantId,
+    StaticId,
+    ConstId,
+    FunctionId,
+    TraitId,
+    TypeAliasId,
+    MacroDefId,
+    ImplId
+);
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum VariantId {
+    EnumVariantId(EnumVariantId),
+    StructId(StructId),
+}
+impl_froms!(VariantId: EnumVariantId, StructId);
+
 trait Intern {
     type ID;
-    fn intern(self, db: &impl db::DefDatabase2) -> Self::ID;
+    fn intern(self, db: &impl db::DefDatabase) -> Self::ID;
 }
 
 pub trait Lookup {
     type Data;
-    fn lookup(&self, db: &impl db::DefDatabase2) -> Self::Data;
+    fn lookup(&self, db: &impl db::DefDatabase) -> Self::Data;
 }
 
 pub trait HasModule {
-    fn module(&self, db: &impl db::DefDatabase2) -> ModuleId;
+    fn module(&self, db: &impl db::DefDatabase) -> ModuleId;
 }
 
 impl HasModule for FunctionLoc {
-    fn module(&self, db: &impl db::DefDatabase2) -> ModuleId {
+    fn module(&self, db: &impl db::DefDatabase) -> ModuleId {
         match self.container {
             ContainerId::ModuleId(it) => it,
             ContainerId::ImplId(it) => it.module(db),
@@ -501,7 +463,7 @@ impl HasModule for FunctionLoc {
 }
 
 impl HasModule for TypeAliasLoc {
-    fn module(&self, db: &impl db::DefDatabase2) -> ModuleId {
+    fn module(&self, db: &impl db::DefDatabase) -> ModuleId {
         match self.container {
             ContainerId::ModuleId(it) => it,
             ContainerId::ImplId(it) => it.module(db),
@@ -511,7 +473,7 @@ impl HasModule for TypeAliasLoc {
 }
 
 impl HasModule for ConstLoc {
-    fn module(&self, db: &impl db::DefDatabase2) -> ModuleId {
+    fn module(&self, db: &impl db::DefDatabase) -> ModuleId {
         match self.container {
             ContainerId::ModuleId(it) => it,
             ContainerId::ImplId(it) => it.module(db),
@@ -520,15 +482,31 @@ impl HasModule for ConstLoc {
     }
 }
 
+impl HasModule for AdtId {
+    fn module(&self, db: &impl db::DefDatabase) -> ModuleId {
+        match self {
+            AdtId::StructId(it) => it.0.module(db),
+            AdtId::UnionId(it) => it.0.module(db),
+            AdtId::EnumId(it) => it.module(db),
+        }
+    }
+}
+
+impl HasModule for StaticLoc {
+    fn module(&self, _db: &impl db::DefDatabase) -> ModuleId {
+        self.container
+    }
+}
+
 pub trait HasSource {
     type Value;
-    fn source(&self, db: &impl db::DefDatabase2) -> Source<Self::Value>;
+    fn source(&self, db: &impl db::DefDatabase) -> Source<Self::Value>;
 }
 
 impl HasSource for FunctionLoc {
     type Value = ast::FnDef;
 
-    fn source(&self, db: &impl db::DefDatabase2) -> Source<ast::FnDef> {
+    fn source(&self, db: &impl db::DefDatabase) -> Source<ast::FnDef> {
         let node = self.ast_id.to_node(db);
         Source::new(self.ast_id.file_id(), node)
     }
@@ -537,7 +515,7 @@ impl HasSource for FunctionLoc {
 impl HasSource for TypeAliasLoc {
     type Value = ast::TypeAliasDef;
 
-    fn source(&self, db: &impl db::DefDatabase2) -> Source<ast::TypeAliasDef> {
+    fn source(&self, db: &impl db::DefDatabase) -> Source<ast::TypeAliasDef> {
         let node = self.ast_id.to_node(db);
         Source::new(self.ast_id.file_id(), node)
     }
@@ -546,8 +524,26 @@ impl HasSource for TypeAliasLoc {
 impl HasSource for ConstLoc {
     type Value = ast::ConstDef;
 
-    fn source(&self, db: &impl db::DefDatabase2) -> Source<ast::ConstDef> {
+    fn source(&self, db: &impl db::DefDatabase) -> Source<ast::ConstDef> {
         let node = self.ast_id.to_node(db);
         Source::new(self.ast_id.file_id(), node)
     }
 }
+
+impl HasSource for StaticLoc {
+    type Value = ast::StaticDef;
+
+    fn source(&self, db: &impl db::DefDatabase) -> Source<ast::StaticDef> {
+        let node = self.ast_id.to_node(db);
+        Source::new(self.ast_id.file_id(), node)
+    }
+}
+
+pub trait HasChildSource {
+    type ChildId;
+    type Value;
+    fn child_source(
+        &self,
+        db: &impl db::DefDatabase,
+    ) -> Source<ArenaMap<Self::ChildId, Self::Value>>;
+}
diff --git a/crates/ra_hir_def/src/nameres.rs b/crates/ra_hir_def/src/nameres.rs
index c01e020ef..2359386c2 100644
--- a/crates/ra_hir_def/src/nameres.rs
+++ b/crates/ra_hir_def/src/nameres.rs
@@ -47,8 +47,7 @@
 //! path and, upon success, we run macro expansion and "collect module" phase on
 //! the result
 
-pub mod raw;
-pub mod per_ns;
+pub(crate) mod raw;
 mod collector;
 mod mod_resolution;
 mod path_resolution;
@@ -58,70 +57,63 @@ mod tests;
 
 use std::sync::Arc;
 
-use hir_expand::{ast_id_map::FileAstId, diagnostics::DiagnosticSink, name::Name, MacroDefId};
+use hir_expand::{
+    ast_id_map::FileAstId, diagnostics::DiagnosticSink, either::Either, name::Name, MacroDefId,
+    Source,
+};
 use once_cell::sync::Lazy;
 use ra_arena::Arena;
 use ra_db::{CrateId, Edition, FileId};
 use ra_prof::profile;
 use ra_syntax::ast;
-use rustc_hash::{FxHashMap, FxHashSet};
+use rustc_hash::FxHashMap;
 
 use crate::{
     builtin_type::BuiltinType,
-    db::DefDatabase2,
-    nameres::{
-        diagnostics::DefDiagnostic, path_resolution::ResolveMode, per_ns::PerNs, raw::ImportId,
-    },
+    db::DefDatabase,
+    nameres::{diagnostics::DefDiagnostic, path_resolution::ResolveMode},
     path::Path,
-    AstId, CrateModuleId, FunctionId, ImplId, ModuleDefId, ModuleId, TraitId,
+    per_ns::PerNs,
+    AstId, FunctionId, ImplId, LocalImportId, LocalModuleId, ModuleDefId, ModuleId, TraitId,
 };
 
 /// Contains all top-level defs from a macro-expanded crate
 #[derive(Debug, PartialEq, Eq)]
 pub struct CrateDefMap {
-    krate: CrateId,
-    edition: Edition,
+    pub root: LocalModuleId,
+    pub modules: Arena<LocalModuleId, ModuleData>,
+    pub(crate) krate: CrateId,
     /// The prelude module for this crate. This either comes from an import
     /// marked with the `prelude_import` attribute, or (in the normal case) from
     /// a dependency (`std` or `core`).
-    prelude: Option<ModuleId>,
-    extern_prelude: FxHashMap<Name, ModuleDefId>,
-    root: CrateModuleId,
-    modules: Arena<CrateModuleId, ModuleData>,
-
-    /// Some macros are not well-behavior, which leads to infinite loop
-    /// e.g. macro_rules! foo { ($ty:ty) => { foo!($ty); } }
-    /// We mark it down and skip it in collector
-    ///
-    /// FIXME:
-    /// Right now it only handle a poison macro in a single crate,
-    /// such that if other crate try to call that macro,
-    /// the whole process will do again until it became poisoned in that crate.
-    /// We should handle this macro set globally
-    /// However, do we want to put it as a global variable?
-    poison_macros: FxHashSet<MacroDefId>,
+    pub(crate) prelude: Option<ModuleId>,
+    pub(crate) extern_prelude: FxHashMap<Name, ModuleDefId>,
 
+    edition: Edition,
     diagnostics: Vec<DefDiagnostic>,
 }
 
-impl std::ops::Index<CrateModuleId> for CrateDefMap {
+impl std::ops::Index<LocalModuleId> for CrateDefMap {
     type Output = ModuleData;
-    fn index(&self, id: CrateModuleId) -> &ModuleData {
+    fn index(&self, id: LocalModuleId) -> &ModuleData {
         &self.modules[id]
     }
 }
 
 #[derive(Default, Debug, PartialEq, Eq)]
 pub struct ModuleData {
-    pub parent: Option<CrateModuleId>,
-    pub children: FxHashMap<Name, CrateModuleId>,
+    pub parent: Option<LocalModuleId>,
+    pub children: FxHashMap<Name, LocalModuleId>,
     pub scope: ModuleScope,
+
+    //  FIXME: these can't be both null, we need a three-state enum here.
     /// None for root
     pub declaration: Option<AstId<ast::Module>>,
     /// None for inline modules.
     ///
     /// Note that non-inline modules, by definition, live inside non-macro file.
     pub definition: Option<FileId>,
+
     pub impls: Vec<ImplId>,
 }
 
@@ -177,7 +169,7 @@ impl ModuleScope {
     pub fn macros<'a>(&'a self) -> impl Iterator<Item = (&'a Name, MacroDefId)> + 'a {
         self.items
             .iter()
-            .filter_map(|(name, res)| res.def.get_macros().map(|macro_| (name, macro_)))
+            .filter_map(|(name, res)| res.def.take_macros().map(|macro_| (name, macro_)))
     }
 
     /// Iterate over all legacy textual scoped macros visable at the end of the module
@@ -207,21 +199,21 @@ pub struct Resolution {
     /// None for unresolved
     pub def: PerNs,
     /// ident by which this is imported into local scope.
-    pub import: Option<ImportId>,
+    pub import: Option<LocalImportId>,
 }
 
 impl CrateDefMap {
     pub(crate) fn crate_def_map_query(
         // Note that this doesn't have `+ AstDatabase`!
         // This gurantess that `CrateDefMap` is stable across reparses.
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         krate: CrateId,
     ) -> Arc<CrateDefMap> {
         let _p = profile("crate_def_map_query");
         let def_map = {
             let crate_graph = db.crate_graph();
             let edition = crate_graph.edition(krate);
-            let mut modules: Arena<CrateModuleId, ModuleData> = Arena::default();
+            let mut modules: Arena<LocalModuleId, ModuleData> = Arena::default();
             let root = modules.alloc(ModuleData::default());
             CrateDefMap {
                 krate,
@@ -230,7 +222,6 @@ impl CrateDefMap {
                 prelude: None,
                 root,
                 modules,
-                poison_macros: FxHashSet::default(),
                 diagnostics: Vec::new(),
             }
         };
@@ -238,50 +229,53 @@ impl CrateDefMap {
         Arc::new(def_map)
     }
 
-    pub fn krate(&self) -> CrateId {
-        self.krate
-    }
-
-    pub fn root(&self) -> CrateModuleId {
-        self.root
-    }
-
-    pub fn prelude(&self) -> Option<ModuleId> {
-        self.prelude
-    }
-
-    pub fn extern_prelude(&self) -> &FxHashMap<Name, ModuleDefId> {
-        &self.extern_prelude
-    }
-
     pub fn add_diagnostics(
         &self,
-        db: &impl DefDatabase2,
-        module: CrateModuleId,
+        db: &impl DefDatabase,
+        module: LocalModuleId,
         sink: &mut DiagnosticSink,
     ) {
         self.diagnostics.iter().for_each(|it| it.add_to(db, module, sink))
     }
 
-    pub fn resolve_path(
+    pub fn modules_for_file(&self, file_id: FileId) -> impl Iterator<Item = LocalModuleId> + '_ {
+        self.modules
+            .iter()
+            .filter(move |(_id, data)| data.definition == Some(file_id))
+            .map(|(id, _data)| id)
+    }
+
+    pub(crate) fn resolve_path(
         &self,
-        db: &impl DefDatabase2,
-        original_module: CrateModuleId,
+        db: &impl DefDatabase,
+        original_module: LocalModuleId,
         path: &Path,
     ) -> (PerNs, Option<usize>) {
         let res = self.resolve_path_fp_with_macro(db, ResolveMode::Other, original_module, path);
         (res.resolved_def, res.segment_index)
     }
+}
 
-    pub fn modules(&self) -> impl Iterator<Item = CrateModuleId> + '_ {
-        self.modules.iter().map(|(id, _data)| id)
+impl ModuleData {
+    /// Returns a node which defines this module. That is, a file or a `mod foo {}` with items.
+    pub fn definition_source(
+        &self,
+        db: &impl DefDatabase,
+    ) -> Source<Either<ast::SourceFile, ast::Module>> {
+        if let Some(file_id) = self.definition {
+            let sf = db.parse(file_id).tree();
+            return Source::new(file_id.into(), Either::A(sf));
+        }
+        let decl = self.declaration.unwrap();
+        Source::new(decl.file_id(), Either::B(decl.to_node(db)))
     }
 
-    pub fn modules_for_file(&self, file_id: FileId) -> impl Iterator<Item = CrateModuleId> + '_ {
-        self.modules
-            .iter()
-            .filter(move |(_id, data)| data.definition == Some(file_id))
-            .map(|(id, _data)| id)
+    /// Returns a node which declares this module, either a `mod foo;` or a `mod foo {}`.
+    /// `None` for the crate root.
+    pub fn declaration_source(&self, db: &impl DefDatabase) -> Option<Source<ast::Module>> {
+        let decl = self.declaration?;
+        let value = decl.to_node(db);
+        Some(Source { file_id: decl.file_id(), value })
     }
 }
 
@@ -290,12 +284,12 @@ mod diagnostics {
     use ra_db::RelativePathBuf;
     use ra_syntax::{ast, AstPtr};
 
-    use crate::{db::DefDatabase2, diagnostics::UnresolvedModule, nameres::CrateModuleId, AstId};
+    use crate::{db::DefDatabase, diagnostics::UnresolvedModule, nameres::LocalModuleId, AstId};
 
     #[derive(Debug, PartialEq, Eq)]
     pub(super) enum DefDiagnostic {
         UnresolvedModule {
-            module: CrateModuleId,
+            module: LocalModuleId,
             declaration: AstId<ast::Module>,
             candidate: RelativePathBuf,
         },
@@ -304,8 +298,8 @@ mod diagnostics {
     impl DefDiagnostic {
         pub(super) fn add_to(
             &self,
-            db: &impl DefDatabase2,
-            target_module: CrateModuleId,
+            db: &impl DefDatabase,
+            target_module: LocalModuleId,
             sink: &mut DiagnosticSink,
         ) {
             match self {
diff --git a/crates/ra_hir_def/src/nameres/collector.rs b/crates/ra_hir_def/src/nameres/collector.rs
index aae3dcadf..41becf8df 100644
--- a/crates/ra_hir_def/src/nameres/collector.rs
+++ b/crates/ra_hir_def/src/nameres/collector.rs
@@ -1,4 +1,7 @@
-//! FIXME: write short doc here
+//! The core of the module-level name resolution algorithm.
+//!
+//! `DefCollector::collect` contains the fixed-point iteration loop which
+//! resolves imports and expands macros.
 
 use hir_expand::{
     builtin_macro::find_builtin_macro,
@@ -7,24 +10,25 @@ use hir_expand::{
 };
 use ra_cfg::CfgOptions;
 use ra_db::{CrateId, FileId};
-use ra_syntax::{ast, SmolStr};
-use rustc_hash::FxHashMap;
+use ra_syntax::ast;
+use rustc_hash::{FxHashMap, FxHashSet};
 use test_utils::tested_by;
 
 use crate::{
-    attr::Attr,
-    db::DefDatabase2,
+    attr::Attrs,
+    db::DefDatabase,
     nameres::{
         diagnostics::DefDiagnostic, mod_resolution::ModDir, path_resolution::ReachedFixedPoint,
-        per_ns::PerNs, raw, CrateDefMap, ModuleData, Resolution, ResolveMode,
+        raw, CrateDefMap, ModuleData, Resolution, ResolveMode,
     },
     path::{Path, PathKind},
-    AdtId, AstId, AstItemDef, ConstLoc, ContainerId, CrateModuleId, EnumId, EnumVariantId,
-    FunctionLoc, ImplId, Intern, LocationCtx, ModuleDefId, ModuleId, StaticId, StructId,
+    per_ns::PerNs,
+    AdtId, AstId, AstItemDef, ConstLoc, ContainerId, EnumId, EnumVariantId, FunctionLoc, ImplId,
+    Intern, LocalImportId, LocalModuleId, LocationCtx, ModuleDefId, ModuleId, StaticLoc, StructId,
     StructOrUnionId, TraitId, TypeAliasLoc, UnionId,
 };
 
-pub(super) fn collect_defs(db: &impl DefDatabase2, mut def_map: CrateDefMap) -> CrateDefMap {
+pub(super) fn collect_defs(db: &impl DefDatabase, mut def_map: CrateDefMap) -> CrateDefMap {
     let crate_graph = db.crate_graph();
 
     // populate external prelude
@@ -56,6 +60,7 @@ pub(super) fn collect_defs(db: &impl DefDatabase2, mut def_map: CrateDefMap) ->
         unexpanded_macros: Vec::new(),
         mod_dirs: FxHashMap::default(),
         macro_stack_monitor: MacroStackMonitor::default(),
+        poison_macros: FxHashSet::default(),
         cfg_options,
     };
     collector.collect();
@@ -94,21 +99,32 @@ impl MacroStackMonitor {
 struct DefCollector<'a, DB> {
     db: &'a DB,
     def_map: CrateDefMap,
-    glob_imports: FxHashMap<CrateModuleId, Vec<(CrateModuleId, raw::ImportId)>>,
-    unresolved_imports: Vec<(CrateModuleId, raw::ImportId, raw::ImportData)>,
-    unexpanded_macros: Vec<(CrateModuleId, AstId<ast::MacroCall>, Path)>,
-    mod_dirs: FxHashMap<CrateModuleId, ModDir>,
+    glob_imports: FxHashMap<LocalModuleId, Vec<(LocalModuleId, LocalImportId)>>,
+    unresolved_imports: Vec<(LocalModuleId, LocalImportId, raw::ImportData)>,
+    unexpanded_macros: Vec<(LocalModuleId, AstId<ast::MacroCall>, Path)>,
+    mod_dirs: FxHashMap<LocalModuleId, ModDir>,
 
     /// Some macro use `$tt:tt which mean we have to handle the macro perfectly
     /// To prevent stack overflow, we add a deep counter here for prevent that.
     macro_stack_monitor: MacroStackMonitor,
+    /// Some macros are not well-behavior, which leads to infinite loop
+    /// e.g. macro_rules! foo { ($ty:ty) => { foo!($ty); } }
+    /// We mark it down and skip it in collector
+    ///
+    /// FIXME:
+    /// Right now it only handle a poison macro in a single crate,
+    /// such that if other crate try to call that macro,
+    /// the whole process will do again until it became poisoned in that crate.
+    /// We should handle this macro set globally
+    /// However, do we want to put it as a global variable?
+    poison_macros: FxHashSet<MacroDefId>,
 
     cfg_options: &'a CfgOptions,
 }
 
 impl<DB> DefCollector<'_, DB>
 where
-    DB: DefDatabase2,
+    DB: DefDatabase,
 {
     fn collect(&mut self) {
         let crate_graph = self.db.crate_graph();
@@ -173,7 +189,7 @@ where
     /// ```
     fn define_macro(
         &mut self,
-        module_id: CrateModuleId,
+        module_id: LocalModuleId,
         name: Name,
         macro_: MacroDefId,
         export: bool,
@@ -200,7 +216,7 @@ where
     /// the definition of current module.
     /// And also, `macro_use` on a module will import all legacy macros visable inside to
     /// current legacy scope, with possible shadowing.
-    fn define_legacy_macro(&mut self, module_id: CrateModuleId, name: Name, macro_: MacroDefId) {
+    fn define_legacy_macro(&mut self, module_id: LocalModuleId, name: Name, macro_: MacroDefId) {
         // Always shadowing
         self.def_map.modules[module_id].scope.legacy_macros.insert(name, macro_);
     }
@@ -208,7 +224,7 @@ where
     /// Import macros from `#[macro_use] extern crate`.
     fn import_macros_from_extern_crate(
         &mut self,
-        current_module_id: CrateModuleId,
+        current_module_id: LocalModuleId,
         import: &raw::ImportData,
     ) {
         log::debug!(
@@ -235,7 +251,7 @@ where
     /// Exported macros are just all macros in the root module scope.
     /// Note that it contains not only all `#[macro_export]` macros, but also all aliases
     /// created by `use` in the root module, ignoring the visibility of `use`.
-    fn import_all_macros_exported(&mut self, current_module_id: CrateModuleId, krate: CrateId) {
+    fn import_all_macros_exported(&mut self, current_module_id: LocalModuleId, krate: CrateId) {
         let def_map = self.db.crate_def_map(krate);
         for (name, def) in def_map[def_map.root].scope.macros() {
             // `macro_use` only bring things into legacy scope.
@@ -265,7 +281,7 @@ where
 
     fn resolve_import(
         &self,
-        module_id: CrateModuleId,
+        module_id: LocalModuleId,
         import: &raw::ImportData,
     ) -> (PerNs, ReachedFixedPoint) {
         log::debug!("resolving import: {:?} ({:?})", import, self.def_map.edition);
@@ -291,9 +307,9 @@ where
 
     fn record_resolved_import(
         &mut self,
-        module_id: CrateModuleId,
+        module_id: LocalModuleId,
         def: PerNs,
-        import_id: raw::ImportId,
+        import_id: LocalImportId,
         import: &raw::ImportData,
     ) {
         if import.is_glob {
@@ -387,8 +403,8 @@ where
 
     fn update(
         &mut self,
-        module_id: CrateModuleId,
-        import: Option<raw::ImportId>,
+        module_id: LocalModuleId,
+        import: Option<LocalImportId>,
         resolutions: &[(Name, Resolution)],
     ) {
         self.update_recursive(module_id, import, resolutions, 0)
@@ -396,8 +412,8 @@ where
 
     fn update_recursive(
         &mut self,
-        module_id: CrateModuleId,
-        import: Option<raw::ImportId>,
+        module_id: LocalModuleId,
+        import: Option<LocalImportId>,
         resolutions: &[(Name, Resolution)],
         depth: usize,
     ) {
@@ -463,7 +479,7 @@ where
                 path,
             );
 
-            if let Some(def) = resolved_res.resolved_def.get_macros() {
+            if let Some(def) = resolved_res.resolved_def.take_macros() {
                 let call_id = self.db.intern_macro(MacroCallLoc { def, ast_id: *ast_id });
                 resolved.push((*module_id, call_id, def));
                 res = ReachedFixedPoint::No;
@@ -484,11 +500,11 @@ where
 
     fn collect_macro_expansion(
         &mut self,
-        module_id: CrateModuleId,
+        module_id: LocalModuleId,
         macro_call_id: MacroCallId,
         macro_def_id: MacroDefId,
     ) {
-        if self.def_map.poison_macros.contains(&macro_def_id) {
+        if self.poison_macros.contains(&macro_def_id) {
             return;
         }
 
@@ -508,7 +524,7 @@ where
             .collect(raw_items.items());
         } else {
             log::error!("Too deep macro expansion: {:?}", macro_call_id);
-            self.def_map.poison_macros.insert(macro_def_id);
+            self.poison_macros.insert(macro_def_id);
         }
 
         self.macro_stack_monitor.decrease(macro_def_id);
@@ -522,7 +538,7 @@ where
 /// Walks a single module, populating defs, imports and macros
 struct ModCollector<'a, D> {
     def_collector: D,
-    module_id: CrateModuleId,
+    module_id: LocalModuleId,
     file_id: HirFileId,
     raw_items: &'a raw::RawItems,
     mod_dir: ModDir,
@@ -530,7 +546,7 @@ struct ModCollector<'a, D> {
 
 impl<DB> ModCollector<'_, &'_ mut DefCollector<'_, DB>>
 where
-    DB: DefDatabase2,
+    DB: DefDatabase,
 {
     fn collect(&mut self, items: &[raw::RawItem]) {
         // Note: don't assert that inserted value is fresh: it's simply not true
@@ -549,7 +565,7 @@ where
         // `#[macro_use] extern crate` is hoisted to imports macros before collecting
         // any other items.
         for item in items {
-            if self.is_cfg_enabled(item.attrs()) {
+            if self.is_cfg_enabled(&item.attrs) {
                 if let raw::RawItemKind::Import(import_id) = item.kind {
                     let import = self.raw_items[import_id].clone();
                     if import.is_extern_crate && import.is_macro_use {
@@ -560,10 +576,10 @@ where
         }
 
         for item in items {
-            if self.is_cfg_enabled(item.attrs()) {
+            if self.is_cfg_enabled(&item.attrs) {
                 match item.kind {
                     raw::RawItemKind::Module(m) => {
-                        self.collect_module(&self.raw_items[m], item.attrs())
+                        self.collect_module(&self.raw_items[m], &item.attrs)
                     }
                     raw::RawItemKind::Import(import_id) => self
                         .def_collector
@@ -585,9 +601,9 @@ where
         }
     }
 
-    fn collect_module(&mut self, module: &raw::ModuleData, attrs: &[Attr]) {
-        let path_attr = self.path_attr(attrs);
-        let is_macro_use = self.is_macro_use(attrs);
+    fn collect_module(&mut self, module: &raw::ModuleData, attrs: &Attrs) {
+        let path_attr = attrs.by_key("path").string_value();
+        let is_macro_use = attrs.by_key("macro_use").exists();
         match module {
             // inline module, just recurse
             raw::ModuleData::Definition { name, items, ast_id } => {
@@ -647,7 +663,7 @@ where
         name: Name,
         declaration: AstId<ast::Module>,
         definition: Option<FileId>,
-    ) -> CrateModuleId {
+    ) -> LocalModuleId {
         let modules = &mut self.def_collector.def_map.modules;
         let res = modules.alloc(ModuleData::default());
         modules[res].parent = Some(self.module_id);
@@ -702,7 +718,10 @@ where
                 PerNs::values(def.into())
             }
             raw::DefKind::Static(ast_id) => {
-                PerNs::values(StaticId::from_ast_id(ctx, ast_id).into())
+                let def = StaticLoc { container: module, ast_id: AstId::new(self.file_id, ast_id) }
+                    .intern(self.def_collector.db);
+
+                PerNs::values(def.into())
             }
             raw::DefKind::Trait(ast_id) => PerNs::types(TraitId::from_ast_id(ctx, ast_id).into()),
             raw::DefKind::TypeAlias(ast_id) => {
@@ -772,23 +791,19 @@ where
         self.def_collector.unexpanded_macros.push((self.module_id, ast_id, path));
     }
 
-    fn import_all_legacy_macros(&mut self, module_id: CrateModuleId) {
+    fn import_all_legacy_macros(&mut self, module_id: LocalModuleId) {
         let macros = self.def_collector.def_map[module_id].scope.legacy_macros.clone();
         for (name, macro_) in macros {
             self.def_collector.define_legacy_macro(self.module_id, name.clone(), macro_);
         }
     }
 
-    fn is_cfg_enabled(&self, attrs: &[Attr]) -> bool {
-        attrs.iter().all(|attr| attr.is_cfg_enabled(&self.def_collector.cfg_options) != Some(false))
-    }
-
-    fn path_attr<'a>(&self, attrs: &'a [Attr]) -> Option<&'a SmolStr> {
-        attrs.iter().find_map(|attr| attr.as_path())
-    }
-
-    fn is_macro_use<'a>(&self, attrs: &'a [Attr]) -> bool {
-        attrs.iter().any(|attr| attr.is_simple_atom("macro_use"))
+    fn is_cfg_enabled(&self, attrs: &Attrs) -> bool {
+        // FIXME: handle cfg_attr :-)
+        attrs
+            .by_key("cfg")
+            .tt_values()
+            .all(|tt| self.def_collector.cfg_options.is_cfg_enabled(tt) != Some(false))
     }
 }
 
@@ -802,15 +817,15 @@ mod tests {
     use ra_db::{fixture::WithFixture, SourceDatabase};
     use rustc_hash::FxHashSet;
 
-    use crate::{db::DefDatabase2, test_db::TestDB};
+    use crate::{db::DefDatabase, test_db::TestDB};
 
     use super::*;
 
     fn do_collect_defs(
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         def_map: CrateDefMap,
         monitor: MacroStackMonitor,
-    ) -> CrateDefMap {
+    ) -> (CrateDefMap, FxHashSet<MacroDefId>) {
         let mut collector = DefCollector {
             db,
             def_map,
@@ -819,19 +834,24 @@ mod tests {
             unexpanded_macros: Vec::new(),
             mod_dirs: FxHashMap::default(),
             macro_stack_monitor: monitor,
+            poison_macros: FxHashSet::default(),
             cfg_options: &CfgOptions::default(),
         };
         collector.collect();
-        collector.finish()
+        (collector.def_map, collector.poison_macros)
     }
 
-    fn do_limited_resolve(code: &str, limit: u32, poison_limit: u32) -> CrateDefMap {
+    fn do_limited_resolve(
+        code: &str,
+        limit: u32,
+        poison_limit: u32,
+    ) -> (CrateDefMap, FxHashSet<MacroDefId>) {
         let (db, _file_id) = TestDB::with_single_file(&code);
         let krate = db.test_crate();
 
         let def_map = {
             let edition = db.crate_graph().edition(krate);
-            let mut modules: Arena<CrateModuleId, ModuleData> = Arena::default();
+            let mut modules: Arena<LocalModuleId, ModuleData> = Arena::default();
             let root = modules.alloc(ModuleData::default());
             CrateDefMap {
                 krate,
@@ -840,7 +860,6 @@ mod tests {
                 prelude: None,
                 root,
                 modules,
-                poison_macros: FxHashSet::default(),
                 diagnostics: Vec::new(),
             }
         };
@@ -870,7 +889,7 @@ foo!(KABOOM);
 
     #[test]
     fn test_macro_expand_poisoned() {
-        let def = do_limited_resolve(
+        let (_, poison_macros) = do_limited_resolve(
             r#"
         macro_rules! foo {
             ($ty:ty) => { foo!($ty); }
@@ -881,12 +900,12 @@ foo!(KABOOM);
             16,
         );
 
-        assert_eq!(def.poison_macros.len(), 1);
+        assert_eq!(poison_macros.len(), 1);
     }
 
     #[test]
     fn test_macro_expand_normal() {
-        let def = do_limited_resolve(
+        let (_, poison_macros) = do_limited_resolve(
             r#"
         macro_rules! foo {
             ($ident:ident) => { struct $ident {} }
@@ -897,6 +916,6 @@ foo!(Bar);
             16,
         );
 
-        assert_eq!(def.poison_macros.len(), 0);
+        assert_eq!(poison_macros.len(), 0);
     }
 }
diff --git a/crates/ra_hir_def/src/nameres/mod_resolution.rs b/crates/ra_hir_def/src/nameres/mod_resolution.rs
index b3b1379d0..14fb8ba3a 100644
--- a/crates/ra_hir_def/src/nameres/mod_resolution.rs
+++ b/crates/ra_hir_def/src/nameres/mod_resolution.rs
@@ -3,7 +3,7 @@ use hir_expand::name::Name;
 use ra_db::{FileId, RelativePathBuf};
 use ra_syntax::SmolStr;
 
-use crate::{db::DefDatabase2, HirFileId};
+use crate::{db::DefDatabase, HirFileId};
 
 #[derive(Clone, Debug)]
 pub(super) struct ModDir {
@@ -40,7 +40,7 @@ impl ModDir {
 
     pub(super) fn resolve_declaration(
         &self,
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         file_id: HirFileId,
         name: &Name,
         attr_path: Option<&SmolStr>,
diff --git a/crates/ra_hir_def/src/nameres/path_resolution.rs b/crates/ra_hir_def/src/nameres/path_resolution.rs
index 95692f826..9455f22bb 100644
--- a/crates/ra_hir_def/src/nameres/path_resolution.rs
+++ b/crates/ra_hir_def/src/nameres/path_resolution.rs
@@ -15,10 +15,11 @@ use ra_db::Edition;
 use test_utils::tested_by;
 
 use crate::{
-    db::DefDatabase2,
-    nameres::{per_ns::PerNs, CrateDefMap},
+    db::DefDatabase,
+    nameres::CrateDefMap,
     path::{Path, PathKind},
-    AdtId, CrateModuleId, EnumVariantId, ModuleDefId, ModuleId,
+    per_ns::PerNs,
+    AdtId, EnumVariantId, LocalModuleId, ModuleDefId, ModuleId,
 };
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -63,9 +64,9 @@ impl CrateDefMap {
     // the result.
     pub(super) fn resolve_path_fp_with_macro(
         &self,
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         mode: ResolveMode,
-        original_module: CrateModuleId,
+        original_module: LocalModuleId,
         path: &Path,
     ) -> ResolvePathResult {
         let mut segments = path.segments.iter().enumerate();
@@ -216,8 +217,8 @@ impl CrateDefMap {
 
     fn resolve_name_in_module(
         &self,
-        db: &impl DefDatabase2,
-        module: CrateModuleId,
+        db: &impl DefDatabase,
+        module: LocalModuleId,
         name: &Name,
     ) -> PerNs {
         // Resolve in:
@@ -243,7 +244,7 @@ impl CrateDefMap {
         from_crate_root.or(from_extern_prelude)
     }
 
-    fn resolve_in_prelude(&self, db: &impl DefDatabase2, name: &Name) -> PerNs {
+    fn resolve_in_prelude(&self, db: &impl DefDatabase, name: &Name) -> PerNs {
         if let Some(prelude) = self.prelude {
             let keep;
             let def_map = if prelude.krate == self.krate {
diff --git a/crates/ra_hir_def/src/nameres/raw.rs b/crates/ra_hir_def/src/nameres/raw.rs
index 7c68fd638..401af031c 100644
--- a/crates/ra_hir_def/src/nameres/raw.rs
+++ b/crates/ra_hir_def/src/nameres/raw.rs
@@ -1,4 +1,9 @@
-//! FIXME: write short doc here
+//! Lowers syntax tree of a rust file into a raw representation of containing
+//! items, *without* attaching them to a module structure.
+//!
+//! That is, raw items don't have semantics, just as syntax, but, unlike syntax,
+//! they don't change with trivial source code edits, making them a great tool
+//! for building salsa recomputation firewalls.
 
 use std::{ops::Index, sync::Arc};
 
@@ -12,11 +17,14 @@ use hir_expand::{
 use ra_arena::{impl_arena_id, map::ArenaMap, Arena, RawId};
 use ra_syntax::{
     ast::{self, AttrsOwner, NameOwner},
-    AstNode, AstPtr, SourceFile,
+    AstNode, AstPtr,
 };
 use test_utils::tested_by;
 
-use crate::{attr::Attr, db::DefDatabase2, path::Path, FileAstId, HirFileId, ModuleSource, Source};
+use crate::{
+    attr::Attrs, db::DefDatabase, path::Path, trace::Trace, FileAstId, HirFileId, LocalImportId,
+    Source,
+};
 
 /// `RawItems` is a set of top-level items in a file (except for impls).
 ///
@@ -25,7 +33,7 @@ use crate::{attr::Attr, db::DefDatabase2, path::Path, FileAstId, HirFileId, Modu
 #[derive(Debug, Default, PartialEq, Eq)]
 pub struct RawItems {
     modules: Arena<Module, ModuleData>,
-    imports: Arena<ImportId, ImportData>,
+    imports: Arena<LocalImportId, ImportData>,
     defs: Arena<Def, DefData>,
     macros: Arena<Macro, MacroData>,
     impls: Arena<Impl, ImplData>,
@@ -35,47 +43,33 @@ pub struct RawItems {
 
 #[derive(Debug, Default, PartialEq, Eq)]
 pub struct ImportSourceMap {
-    map: ArenaMap<ImportId, ImportSourcePtr>,
+    map: ArenaMap<LocalImportId, ImportSourcePtr>,
 }
 
 type ImportSourcePtr = Either<AstPtr<ast::UseTree>, AstPtr<ast::ExternCrateItem>>;
-type ImportSource = Either<ast::UseTree, ast::ExternCrateItem>;
-
-fn to_node(ptr: ImportSourcePtr, file: &SourceFile) -> ImportSource {
-    ptr.map(|ptr| ptr.to_node(file.syntax()), |ptr| ptr.to_node(file.syntax()))
-}
 
 impl ImportSourceMap {
-    fn insert(&mut self, import: ImportId, ptr: ImportSourcePtr) {
-        self.map.insert(import, ptr)
-    }
-
-    pub fn get(&self, source: &ModuleSource, import: ImportId) -> ImportSource {
-        let file = match source {
-            ModuleSource::SourceFile(file) => file.clone(),
-            ModuleSource::Module(m) => m.syntax().ancestors().find_map(SourceFile::cast).unwrap(),
-        };
-
-        to_node(self.map[import], &file)
+    pub fn get(&self, import: LocalImportId) -> ImportSourcePtr {
+        self.map[import].clone()
     }
 }
 
 impl RawItems {
     pub(crate) fn raw_items_query(
-        db: &(impl DefDatabase2 + AstDatabase),
+        db: &(impl DefDatabase + AstDatabase),
         file_id: HirFileId,
     ) -> Arc<RawItems> {
         db.raw_items_with_source_map(file_id).0
     }
 
     pub(crate) fn raw_items_with_source_map_query(
-        db: &(impl DefDatabase2 + AstDatabase),
+        db: &(impl DefDatabase + AstDatabase),
         file_id: HirFileId,
     ) -> (Arc<RawItems>, Arc<ImportSourceMap>) {
         let mut collector = RawItemsCollector {
             raw_items: RawItems::default(),
             source_ast_id_map: db.ast_id_map(file_id),
-            source_map: ImportSourceMap::default(),
+            imports: Trace::new(),
             file_id,
             hygiene: Hygiene::new(db, file_id),
         };
@@ -86,7 +80,11 @@ impl RawItems {
                 collector.process_module(None, item_list);
             }
         }
-        (Arc::new(collector.raw_items), Arc::new(collector.source_map))
+        let mut raw_items = collector.raw_items;
+        let (arena, map) = collector.imports.into_arena_and_map();
+        raw_items.imports = arena;
+        let source_map = ImportSourceMap { map };
+        (Arc::new(raw_items), Arc::new(source_map))
     }
 
     pub(super) fn items(&self) -> &[RawItem] {
@@ -101,9 +99,9 @@ impl Index<Module> for RawItems {
     }
 }
 
-impl Index<ImportId> for RawItems {
+impl Index<LocalImportId> for RawItems {
     type Output = ImportData;
-    fn index(&self, idx: ImportId) -> &ImportData {
+    fn index(&self, idx: LocalImportId) -> &ImportData {
         &self.imports[idx]
     }
 }
@@ -129,25 +127,16 @@ impl Index<Impl> for RawItems {
     }
 }
 
-// Avoid heap allocation on items without attributes.
-type Attrs = Option<Arc<[Attr]>>;
-
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub(super) struct RawItem {
-    attrs: Attrs,
+    pub(super) attrs: Attrs,
     pub(super) kind: RawItemKind,
 }
 
-impl RawItem {
-    pub(super) fn attrs(&self) -> &[Attr] {
-        self.attrs.as_ref().map_or(&[], |it| &*it)
-    }
-}
-
 #[derive(Debug, PartialEq, Eq, Clone, Copy)]
 pub(super) enum RawItemKind {
     Module(Module),
-    Import(ImportId),
+    Import(LocalImportId),
     Def(Def),
     Macro(Macro),
     Impl(Impl),
@@ -163,10 +152,6 @@ pub(super) enum ModuleData {
     Definition { name: Name, ast_id: FileAstId<ast::Module>, items: Vec<RawItem> },
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct ImportId(RawId);
-impl_arena_id!(ImportId);
-
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct ImportData {
     pub(super) path: Path,
@@ -223,8 +208,8 @@ pub(super) struct ImplData {
 
 struct RawItemsCollector {
     raw_items: RawItems,
+    imports: Trace<LocalImportId, ImportData, ImportSourcePtr>,
     source_ast_id_map: Arc<AstIdMap>,
-    source_map: ImportSourceMap,
     file_id: HirFileId,
     hygiene: Hygiene,
 }
@@ -408,8 +393,7 @@ impl RawItemsCollector {
         data: ImportData,
         source: ImportSourcePtr,
     ) {
-        let import = self.raw_items.imports.alloc(data);
-        self.source_map.insert(import, source);
+        let import = self.imports.alloc(|| source, || data);
         self.push_item(current_module, attrs, RawItemKind::Import(import))
     }
 
@@ -425,6 +409,6 @@ impl RawItemsCollector {
     }
 
     fn parse_attrs(&self, item: &impl ast::AttrsOwner) -> Attrs {
-        Attr::from_attrs_owner(item, &self.hygiene)
+        Attrs::new(item, &self.hygiene)
     }
 }
diff --git a/crates/ra_hir_def/src/nameres/tests.rs b/crates/ra_hir_def/src/nameres/tests.rs
index 256f7d4be..f502f1cb3 100644
--- a/crates/ra_hir_def/src/nameres/tests.rs
+++ b/crates/ra_hir_def/src/nameres/tests.rs
@@ -10,7 +10,7 @@ use insta::assert_snapshot;
 use ra_db::{fixture::WithFixture, SourceDatabase};
 use test_utils::covers;
 
-use crate::{db::DefDatabase2, nameres::*, test_db::TestDB, CrateModuleId};
+use crate::{db::DefDatabase, nameres::*, test_db::TestDB, LocalModuleId};
 
 fn def_map(fixtute: &str) -> String {
     let dm = compute_crate_def_map(fixtute);
@@ -25,10 +25,10 @@ fn compute_crate_def_map(fixture: &str) -> Arc<CrateDefMap> {
 
 fn render_crate_def_map(map: &CrateDefMap) -> String {
     let mut buf = String::new();
-    go(&mut buf, map, "\ncrate", map.root());
+    go(&mut buf, map, "\ncrate", map.root);
     return buf.trim().to_string();
 
-    fn go(buf: &mut String, map: &CrateDefMap, path: &str, module: CrateModuleId) {
+    fn go(buf: &mut String, map: &CrateDefMap, path: &str, module: LocalModuleId) {
         *buf += path;
         *buf += "\n";
 
diff --git a/crates/ra_hir_def/src/nameres/tests/mod_resolution.rs b/crates/ra_hir_def/src/nameres/tests/mod_resolution.rs
index eb7b85c07..e11530062 100644
--- a/crates/ra_hir_def/src/nameres/tests/mod_resolution.rs
+++ b/crates/ra_hir_def/src/nameres/tests/mod_resolution.rs
@@ -665,7 +665,7 @@ fn unresolved_module_diagnostics() {
         @r###"
     [
         UnresolvedModule {
-            module: CrateModuleId(
+            module: LocalModuleId(
                 0,
             ),
             declaration: AstId {
diff --git a/crates/ra_hir_def/src/path.rs b/crates/ra_hir_def/src/path.rs
index 626ebffdc..0e606fd0e 100644
--- a/crates/ra_hir_def/src/path.rs
+++ b/crates/ra_hir_def/src/path.rs
@@ -1,4 +1,4 @@
-//! FIXME: write short doc here
+//! A desugared representation of paths like `crate::foo` or `<Type as Trait>::bar`.
 
 use std::{iter, sync::Arc};
 
@@ -66,7 +66,7 @@ pub enum PathKind {
 
 impl Path {
     /// Calls `cb` with all paths, represented by this use item.
-    pub fn expand_use_item(
+    pub(crate) fn expand_use_item(
         item_src: Source<ast::UseItem>,
         hygiene: &Hygiene,
         mut cb: impl FnMut(Path, &ast::UseTree, bool, Option<Name>),
@@ -76,7 +76,10 @@ impl Path {
         }
     }
 
-    pub fn from_simple_segments(kind: PathKind, segments: impl IntoIterator<Item = Name>) -> Path {
+    pub(crate) fn from_simple_segments(
+        kind: PathKind,
+        segments: impl IntoIterator<Item = Name>,
+    ) -> Path {
         Path {
             kind,
             segments: segments
@@ -94,7 +97,7 @@ impl Path {
 
     /// Converts an `ast::Path` to `Path`. Works with use trees.
     /// It correctly handles `$crate` based path from macro call.
-    pub fn from_src(mut path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
+    pub(crate) fn from_src(mut path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
         let mut kind = PathKind::Plain;
         let mut segments = Vec::new();
         loop {
@@ -192,7 +195,7 @@ impl Path {
     }
 
     /// Converts an `ast::NameRef` into a single-identifier `Path`.
-    pub fn from_name_ref(name_ref: &ast::NameRef) -> Path {
+    pub(crate) fn from_name_ref(name_ref: &ast::NameRef) -> Path {
         name_ref.as_name().into()
     }
 
@@ -227,7 +230,7 @@ impl Path {
 }
 
 impl GenericArgs {
-    pub fn from_ast(node: ast::TypeArgList) -> Option<GenericArgs> {
+    pub(crate) fn from_ast(node: ast::TypeArgList) -> Option<GenericArgs> {
         let mut args = Vec::new();
         for type_arg in node.type_args() {
             let type_ref = TypeRef::from_ast_opt(type_arg.type_ref());
diff --git a/crates/ra_hir_def/src/nameres/per_ns.rs b/crates/ra_hir_def/src/per_ns.rs
index 717ed1ef9..00e866bf9 100644
--- a/crates/ra_hir_def/src/nameres/per_ns.rs
+++ b/crates/ra_hir_def/src/per_ns.rs
@@ -1,4 +1,7 @@
-//! FIXME: write short doc here
+//! In rust, it is possible to have a value, a type and a macro with the same
+//! name without conflicts.
+//!
+//! `PerNs` (per namespace) captures this.
 
 use hir_expand::MacroDefId;
 
@@ -44,10 +47,6 @@ impl PerNs {
         self.types.is_none() && self.values.is_none() && self.macros.is_none()
     }
 
-    pub fn is_all(&self) -> bool {
-        self.types.is_some() && self.values.is_some() && self.macros.is_some()
-    }
-
     pub fn take_types(self) -> Option<ModuleDefId> {
         self.types
     }
@@ -56,14 +55,10 @@ impl PerNs {
         self.values
     }
 
-    pub fn get_macros(&self) -> Option<MacroDefId> {
+    pub fn take_macros(self) -> Option<MacroDefId> {
         self.macros
     }
 
-    pub fn only_macros(&self) -> PerNs {
-        PerNs { types: None, values: None, macros: self.macros }
-    }
-
     pub fn or(self, other: PerNs) -> PerNs {
         PerNs {
             types: self.types.or(other.types),
diff --git a/crates/ra_hir_def/src/resolver.rs b/crates/ra_hir_def/src/resolver.rs
index 7b5c3ec06..95b3c926d 100644
--- a/crates/ra_hir_def/src/resolver.rs
+++ b/crates/ra_hir_def/src/resolver.rs
@@ -11,14 +11,15 @@ use rustc_hash::FxHashSet;
 use crate::{
     body::scope::{ExprScopes, ScopeId},
     builtin_type::BuiltinType,
-    db::DefDatabase2,
+    db::DefDatabase,
     expr::{ExprId, PatId},
     generics::GenericParams,
-    nameres::{per_ns::PerNs, CrateDefMap},
+    nameres::CrateDefMap,
     path::{Path, PathKind},
-    AdtId, AstItemDef, ConstId, ContainerId, CrateModuleId, DefWithBodyId, EnumId, EnumVariantId,
-    FunctionId, GenericDefId, ImplId, Lookup, ModuleDefId, ModuleId, StaticId, StructId, TraitId,
-    TypeAliasId,
+    per_ns::PerNs,
+    AdtId, AstItemDef, ConstId, ContainerId, DefWithBodyId, EnumId, EnumVariantId, FunctionId,
+    GenericDefId, HasModule, ImplId, LocalModuleId, Lookup, ModuleDefId, ModuleId, StaticId,
+    StructId, TraitId, TypeAliasId,
 };
 
 #[derive(Debug, Clone, Default)]
@@ -28,20 +29,20 @@ pub struct Resolver {
 
 // FIXME how to store these best
 #[derive(Debug, Clone)]
-pub(crate) struct ModuleItemMap {
+struct ModuleItemMap {
     crate_def_map: Arc<CrateDefMap>,
-    module_id: CrateModuleId,
+    module_id: LocalModuleId,
 }
 
 #[derive(Debug, Clone)]
-pub(crate) struct ExprScope {
+struct ExprScope {
     owner: DefWithBodyId,
     expr_scopes: Arc<ExprScopes>,
     scope_id: ScopeId,
 }
 
 #[derive(Debug, Clone)]
-pub(crate) enum Scope {
+enum Scope {
     /// All the items and imported names of a module
     ModuleScope(ModuleItemMap),
     /// Brings the generic parameters of an item into scope
@@ -87,7 +88,7 @@ pub enum ValueNs {
 
 impl Resolver {
     /// Resolve known trait from std, like `std::futures::Future`
-    pub fn resolve_known_trait(&self, db: &impl DefDatabase2, path: &Path) -> Option<TraitId> {
+    pub fn resolve_known_trait(&self, db: &impl DefDatabase, path: &Path) -> Option<TraitId> {
         let res = self.resolve_module_path(db, path).take_types()?;
         match res {
             ModuleDefId::TraitId(it) => Some(it),
@@ -96,7 +97,7 @@ impl Resolver {
     }
 
     /// Resolve known struct from std, like `std::boxed::Box`
-    pub fn resolve_known_struct(&self, db: &impl DefDatabase2, path: &Path) -> Option<StructId> {
+    pub fn resolve_known_struct(&self, db: &impl DefDatabase, path: &Path) -> Option<StructId> {
         let res = self.resolve_module_path(db, path).take_types()?;
         match res {
             ModuleDefId::AdtId(AdtId::StructId(it)) => Some(it),
@@ -105,7 +106,7 @@ impl Resolver {
     }
 
     /// Resolve known enum from std, like `std::result::Result`
-    pub fn resolve_known_enum(&self, db: &impl DefDatabase2, path: &Path) -> Option<EnumId> {
+    pub fn resolve_known_enum(&self, db: &impl DefDatabase, path: &Path) -> Option<EnumId> {
         let res = self.resolve_module_path(db, path).take_types()?;
         match res {
             ModuleDefId::AdtId(AdtId::EnumId(it)) => Some(it),
@@ -114,7 +115,7 @@ impl Resolver {
     }
 
     /// pub only for source-binder
-    pub fn resolve_module_path(&self, db: &impl DefDatabase2, path: &Path) -> PerNs {
+    pub fn resolve_module_path(&self, db: &impl DefDatabase, path: &Path) -> PerNs {
         let (item_map, module) = match self.module() {
             Some(it) => it,
             None => return PerNs::none(),
@@ -128,7 +129,7 @@ impl Resolver {
 
     pub fn resolve_path_in_type_ns(
         &self,
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         path: &Path,
     ) -> Option<(TypeNs, Option<usize>)> {
         if path.is_type_relative() {
@@ -184,7 +185,7 @@ impl Resolver {
 
     pub fn resolve_path_in_type_ns_fully(
         &self,
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         path: &Path,
     ) -> Option<TypeNs> {
         let (res, unresolved) = self.resolve_path_in_type_ns(db, path)?;
@@ -196,7 +197,7 @@ impl Resolver {
 
     pub fn resolve_path_in_value_ns<'p>(
         &self,
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         path: &'p Path,
     ) -> Option<ResolveValueResult> {
         if path.is_type_relative() {
@@ -296,7 +297,7 @@ impl Resolver {
 
     pub fn resolve_path_in_value_ns_fully(
         &self,
-        db: &impl DefDatabase2,
+        db: &impl DefDatabase,
         path: &Path,
     ) -> Option<ValueNs> {
         match self.resolve_path_in_value_ns(db, path)? {
@@ -305,22 +306,22 @@ impl Resolver {
         }
     }
 
-    pub fn resolve_path_as_macro(&self, db: &impl DefDatabase2, path: &Path) -> Option<MacroDefId> {
+    pub fn resolve_path_as_macro(&self, db: &impl DefDatabase, path: &Path) -> Option<MacroDefId> {
         let (item_map, module) = self.module()?;
-        item_map.resolve_path(db, module, path).0.get_macros()
+        item_map.resolve_path(db, module, path).0.take_macros()
     }
 
-    pub fn process_all_names(&self, db: &impl DefDatabase2, f: &mut dyn FnMut(Name, ScopeDef)) {
+    pub fn process_all_names(&self, db: &impl DefDatabase, f: &mut dyn FnMut(Name, ScopeDef)) {
         for scope in self.scopes.iter().rev() {
             scope.process_names(db, f);
         }
     }
 
-    pub fn traits_in_scope(&self, db: &impl DefDatabase2) -> FxHashSet<TraitId> {
+    pub fn traits_in_scope(&self, db: &impl DefDatabase) -> 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() {
+                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());
                 }
@@ -330,7 +331,7 @@ impl Resolver {
         traits
     }
 
-    fn module(&self) -> Option<(&CrateDefMap, CrateModuleId)> {
+    fn module(&self) -> Option<(&CrateDefMap, LocalModuleId)> {
         self.scopes.iter().rev().find_map(|scope| match scope {
             Scope::ModuleScope(m) => Some((&*m.crate_def_map, m.module_id)),
 
@@ -339,7 +340,7 @@ impl Resolver {
     }
 
     pub fn krate(&self) -> Option<CrateId> {
-        self.module().map(|t| t.0.krate())
+        self.module().map(|t| t.0.krate)
     }
 
     pub fn where_predicates_in_scope<'a>(
@@ -378,7 +379,7 @@ pub enum ScopeDef {
 }
 
 impl Scope {
-    fn process_names(&self, db: &impl DefDatabase2, f: &mut dyn FnMut(Name, ScopeDef)) {
+    fn process_names(&self, db: &impl DefDatabase, f: &mut dyn FnMut(Name, ScopeDef)) {
         match self {
             Scope::ModuleScope(m) => {
                 // FIXME: should we provide `self` here?
@@ -394,10 +395,10 @@ impl Scope {
                 m.crate_def_map[m.module_id].scope.legacy_macros().for_each(|(name, macro_)| {
                     f(name.clone(), ScopeDef::PerNs(PerNs::macros(macro_)));
                 });
-                m.crate_def_map.extern_prelude().iter().for_each(|(name, &def)| {
+                m.crate_def_map.extern_prelude.iter().for_each(|(name, &def)| {
                     f(name.clone(), ScopeDef::PerNs(PerNs::types(def.into())));
                 });
-                if let Some(prelude) = m.crate_def_map.prelude() {
+                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(), ScopeDef::PerNs(res.def));
@@ -425,17 +426,13 @@ impl Scope {
 }
 
 // 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 {
+pub fn resolver_for_expr(db: &impl DefDatabase, 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,
+    db: &impl DefDatabase,
     owner: DefWithBodyId,
     scope_id: Option<ScopeId>,
 ) -> Resolver {
@@ -454,7 +451,7 @@ impl Resolver {
         self
     }
 
-    fn push_generic_params_scope(self, db: &impl DefDatabase2, def: GenericDefId) -> Resolver {
+    fn push_generic_params_scope(self, db: &impl DefDatabase, def: GenericDefId) -> Resolver {
         let params = db.generic_params(def);
         if params.params.is_empty() {
             self
@@ -470,7 +467,7 @@ impl Resolver {
     fn push_module_scope(
         self,
         crate_def_map: Arc<CrateDefMap>,
-        module_id: CrateModuleId,
+        module_id: LocalModuleId,
     ) -> Resolver {
         self.push_scope(Scope::ModuleScope(ModuleItemMap { crate_def_map, module_id }))
     }
@@ -487,32 +484,26 @@ impl Resolver {
 
 pub trait HasResolver {
     /// Builds a resolver for type references inside this def.
-    fn resolver(self, db: &impl DefDatabase2) -> Resolver;
+    fn resolver(self, db: &impl DefDatabase) -> Resolver;
 }
 
 impl HasResolver for ModuleId {
-    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+    fn resolver(self, db: &impl DefDatabase) -> Resolver {
         let def_map = db.crate_def_map(self.krate);
         Resolver::default().push_module_scope(def_map, self.module_id)
     }
 }
 
 impl HasResolver for TraitId {
-    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+    fn resolver(self, db: &impl DefDatabase) -> Resolver {
         self.module(db).resolver(db).push_generic_params_scope(db, self.into())
     }
 }
 
 impl<T: Into<AdtId>> HasResolver for T {
-    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+    fn resolver(self, db: &impl DefDatabase) -> Resolver {
         let def = self.into();
-        let module = match def {
-            AdtId::StructId(it) => it.0.module(db),
-            AdtId::UnionId(it) => it.0.module(db),
-            AdtId::EnumId(it) => it.module(db),
-        };
-
-        module
+        def.module(db)
             .resolver(db)
             .push_generic_params_scope(db, def.into())
             .push_scope(Scope::AdtScope(def))
@@ -520,13 +511,13 @@ impl<T: Into<AdtId>> HasResolver for T {
 }
 
 impl HasResolver for FunctionId {
-    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+    fn resolver(self, db: &impl DefDatabase) -> 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 {
+    fn resolver(self, db: &impl DefDatabase) -> Resolver {
         match self {
             DefWithBodyId::ConstId(c) => c.resolver(db),
             DefWithBodyId::FunctionId(f) => f.resolver(db),
@@ -536,25 +527,25 @@ impl HasResolver for DefWithBodyId {
 }
 
 impl HasResolver for ConstId {
-    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+    fn resolver(self, db: &impl DefDatabase) -> Resolver {
         self.lookup(db).container.resolver(db)
     }
 }
 
 impl HasResolver for StaticId {
-    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
-        self.module(db).resolver(db)
+    fn resolver(self, db: &impl DefDatabase) -> Resolver {
+        self.lookup(db).container.resolver(db)
     }
 }
 
 impl HasResolver for TypeAliasId {
-    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+    fn resolver(self, db: &impl DefDatabase) -> Resolver {
         self.lookup(db).container.resolver(db).push_generic_params_scope(db, self.into())
     }
 }
 
 impl HasResolver for ContainerId {
-    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+    fn resolver(self, db: &impl DefDatabase) -> Resolver {
         match self {
             ContainerId::TraitId(it) => it.resolver(db),
             ContainerId::ImplId(it) => it.resolver(db),
@@ -564,7 +555,7 @@ impl HasResolver for ContainerId {
 }
 
 impl HasResolver for GenericDefId {
-    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+    fn resolver(self, db: &impl DefDatabase) -> Resolver {
         match self {
             GenericDefId::FunctionId(inner) => inner.resolver(db),
             GenericDefId::AdtId(adt) => adt.resolver(db),
@@ -578,7 +569,7 @@ impl HasResolver for GenericDefId {
 }
 
 impl HasResolver for ImplId {
-    fn resolver(self, db: &impl DefDatabase2) -> Resolver {
+    fn resolver(self, db: &impl DefDatabase) -> Resolver {
         self.module(db)
             .resolver(db)
             .push_generic_params_scope(db, self.into())
diff --git a/crates/ra_hir_def/src/test_db.rs b/crates/ra_hir_def/src/test_db.rs
index 8ee8e40d0..439e8a412 100644
--- a/crates/ra_hir_def/src/test_db.rs
+++ b/crates/ra_hir_def/src/test_db.rs
@@ -12,7 +12,7 @@ use ra_db::{salsa, CrateId, FileId, FileLoader, FileLoaderDelegate, RelativePath
     ra_db::SourceDatabaseStorage,
     hir_expand::db::AstDatabaseStorage,
     crate::db::InternDatabaseStorage,
-    crate::db::DefDatabase2Storage
+    crate::db::DefDatabaseStorage
 )]
 #[derive(Debug, Default)]
 pub struct TestDB {
diff --git a/crates/ra_hir_def/src/trace.rs b/crates/ra_hir_def/src/trace.rs
new file mode 100644
index 000000000..2bcd707bc
--- /dev/null
+++ b/crates/ra_hir_def/src/trace.rs
@@ -0,0 +1,59 @@
+//! Trace is a pretty niche data structure which is used when lowering a CST
+//! into HIR.
+//!
+//! Lowering process calculates two bits of information:
+//! * the lowered syntax itself
+//! * a mapping between lowered syntax and original syntax
+//!
+//! Due to the way salsa works, the mapping is usually hot lava, as it contains
+//! absolute offsets. The `Trace` structure (inspired, at least in name, by
+//! Kotlin's `BindingTrace`) allows use the same code to compute both
+//! projections.
+use ra_arena::{map::ArenaMap, Arena, ArenaId, RawId};
+
+pub(crate) struct Trace<ID: ArenaId, T, V> {
+    arena: Option<Arena<ID, T>>,
+    map: Option<ArenaMap<ID, V>>,
+    len: u32,
+}
+
+impl<ID: ra_arena::ArenaId + Copy, T, V> Trace<ID, T, V> {
+    pub(crate) fn new() -> Trace<ID, T, V> {
+        Trace { arena: Some(Arena::default()), map: Some(ArenaMap::default()), len: 0 }
+    }
+
+    pub(crate) fn new_for_arena() -> Trace<ID, T, V> {
+        Trace { arena: Some(Arena::default()), map: None, len: 0 }
+    }
+
+    pub(crate) fn new_for_map() -> Trace<ID, T, V> {
+        Trace { arena: None, map: Some(ArenaMap::default()), len: 0 }
+    }
+
+    pub(crate) fn alloc(&mut self, value: impl FnOnce() -> V, data: impl FnOnce() -> T) -> ID {
+        let id = if let Some(arena) = &mut self.arena {
+            arena.alloc(data())
+        } else {
+            let id = ID::from_raw(RawId::from(self.len));
+            self.len += 1;
+            id
+        };
+
+        if let Some(map) = &mut self.map {
+            map.insert(id, value());
+        }
+        id
+    }
+
+    pub(crate) fn into_arena(mut self) -> Arena<ID, T> {
+        self.arena.take().unwrap()
+    }
+
+    pub(crate) fn into_map(mut self) -> ArenaMap<ID, V> {
+        self.map.take().unwrap()
+    }
+
+    pub(crate) fn into_arena_and_map(mut self) -> (Arena<ID, T>, ArenaMap<ID, V>) {
+        (self.arena.take().unwrap(), self.map.take().unwrap())
+    }
+}
diff --git a/crates/ra_hir_def/src/traits.rs b/crates/ra_hir_def/src/traits.rs
deleted file mode 100644
index 6c2d5b2a9..000000000
--- a/crates/ra_hir_def/src/traits.rs
+++ /dev/null
@@ -1,66 +0,0 @@
-//! HIR for trait definitions.
-
-use std::sync::Arc;
-
-use hir_expand::{
-    name::{AsName, Name},
-    AstId,
-};
-
-use ra_syntax::ast::{self, NameOwner};
-
-use crate::{
-    db::DefDatabase2, AssocItemId, AstItemDef, ConstLoc, ContainerId, FunctionLoc, Intern, TraitId,
-    TypeAliasId, TypeAliasLoc,
-};
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct TraitData {
-    pub name: Option<Name>,
-    pub items: Vec<AssocItemId>,
-    pub auto: bool,
-}
-
-impl TraitData {
-    pub(crate) fn trait_data_query(db: &impl DefDatabase2, tr: TraitId) -> Arc<TraitData> {
-        let src = tr.source(db);
-        let name = src.value.name().map(|n| n.as_name());
-        let auto = src.value.is_auto();
-        let ast_id_map = db.ast_id_map(src.file_id);
-        let items = if let Some(item_list) = src.value.item_list() {
-            item_list
-                .impl_items()
-                .map(|item_node| match item_node {
-                    ast::ImplItem::FnDef(it) => FunctionLoc {
-                        container: ContainerId::TraitId(tr),
-                        ast_id: AstId::new(src.file_id, ast_id_map.ast_id(&it)),
-                    }
-                    .intern(db)
-                    .into(),
-                    ast::ImplItem::ConstDef(it) => ConstLoc {
-                        container: ContainerId::TraitId(tr),
-                        ast_id: AstId::new(src.file_id, ast_id_map.ast_id(&it)),
-                    }
-                    .intern(db)
-                    .into(),
-                    ast::ImplItem::TypeAliasDef(it) => TypeAliasLoc {
-                        container: ContainerId::TraitId(tr),
-                        ast_id: AstId::new(src.file_id, ast_id_map.ast_id(&it)),
-                    }
-                    .intern(db)
-                    .into(),
-                })
-                .collect()
-        } else {
-            Vec::new()
-        };
-        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,
-        })
-    }
-}
diff --git a/crates/ra_hir_def/src/type_ref.rs b/crates/ra_hir_def/src/type_ref.rs
index 8af061116..5f10e9a88 100644
--- a/crates/ra_hir_def/src/type_ref.rs
+++ b/crates/ra_hir_def/src/type_ref.rs
@@ -64,7 +64,7 @@ pub enum TypeBound {
 
 impl TypeRef {
     /// Converts an `ast::TypeRef` to a `hir::TypeRef`.
-    pub fn from_ast(node: ast::TypeRef) -> Self {
+    pub(crate) fn from_ast(node: ast::TypeRef) -> Self {
         match node {
             ast::TypeRef::ParenType(inner) => TypeRef::from_ast_opt(inner.type_ref()),
             ast::TypeRef::TupleType(inner) => {
@@ -113,7 +113,7 @@ impl TypeRef {
         }
     }
 
-    pub fn from_ast_opt(node: Option<ast::TypeRef>) -> Self {
+    pub(crate) fn from_ast_opt(node: Option<ast::TypeRef>) -> Self {
         if let Some(node) = node {
             TypeRef::from_ast(node)
         } else {
@@ -121,7 +121,7 @@ impl TypeRef {
         }
     }
 
-    pub fn unit() -> TypeRef {
+    pub(crate) fn unit() -> TypeRef {
         TypeRef::Tuple(Vec::new())
     }
 }
@@ -135,7 +135,7 @@ pub(crate) fn type_bounds_from_ast(type_bounds_opt: Option<ast::TypeBoundList>)
 }
 
 impl TypeBound {
-    pub fn from_ast(node: ast::TypeBound) -> Self {
+    pub(crate) fn from_ast(node: ast::TypeBound) -> Self {
         match node.kind() {
             ast::TypeBoundKind::PathType(path_type) => {
                 let path = match path_type.path() {