10 files changed, 231 insertions, 207 deletions

diff --git a/crates/ra_hir/src/code_model_api.rs b/crates/ra_hir/src/code_model_api.rs
index 88c13566c..624c25c4d 100644
--- a/crates/ra_hir/src/code_model_api.rs
+++ b/crates/ra_hir/src/code_model_api.rs
@@ -13,7 +13,7 @@ use crate::{
     adt::{EnumVariantId, StructFieldId, VariantDef},
     generics::GenericParams,
     docs::{Documentation, Docs, docs_from_ast},
-    ids::{FunctionId, StructId, EnumId, AstItemDef, ConstId, StaticId, TraitId, TypeId},
+    ids::{FunctionId, StructId, EnumId, AstItemDef, ConstId, StaticId, TraitId, TypeAliasId},
     impl_block::ImplBlock,
     resolve::Resolver,
     diagnostics::DiagnosticSink,
@@ -672,7 +672,7 @@ impl Docs for Trait {
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct TypeAlias {
-    pub(crate) id: TypeId,
+    pub(crate) id: TypeAliasId,
 }
 
 impl TypeAlias {
diff --git a/crates/ra_hir/src/code_model_impl/module.rs b/crates/ra_hir/src/code_model_impl/module.rs
index 790e2b80f..0edb8ade5 100644
--- a/crates/ra_hir/src/code_model_impl/module.rs
+++ b/crates/ra_hir/src/code_model_impl/module.rs
@@ -1,18 +1,18 @@
 use ra_db::FileId;
-use ra_syntax::{ast, TreeArc, AstNode};
+use ra_syntax::{ast, TreeArc};
 
 use crate::{
-    Module, ModuleSource, Name,
+    Module, ModuleSource, Name, AstId,
     nameres::{CrateModuleId, ImportId},
     HirDatabase, DefDatabase,
-    HirFileId, SourceItemId,
+    HirFileId,
 };
 
 impl ModuleSource {
     pub(crate) fn new(
         db: &impl DefDatabase,
         file_id: Option<FileId>,
-        decl_id: Option<SourceItemId>,
+        decl_id: Option<AstId<ast::Module>>,
     ) -> ModuleSource {
         match (file_id, decl_id) {
             (Some(file_id), _) => {
@@ -20,8 +20,7 @@ impl ModuleSource {
                 ModuleSource::SourceFile(source_file)
             }
             (None, Some(item_id)) => {
-                let module = db.file_item(item_id);
-                let module = ast::Module::cast(&*module).unwrap();
+                let module = item_id.to_node(db);
                 assert!(module.item_list().is_some(), "expected inline module");
                 ModuleSource::Module(module.to_owned())
             }
@@ -55,7 +54,7 @@ impl Module {
         let decl_id = def_map[self.module_id].declaration;
         let file_id = def_map[self.module_id].definition;
         let module_source = ModuleSource::new(db, file_id, decl_id);
-        let file_id = file_id.map(HirFileId::from).unwrap_or_else(|| decl_id.unwrap().file_id);
+        let file_id = file_id.map(HirFileId::from).unwrap_or_else(|| decl_id.unwrap().file_id());
         (file_id, module_source)
     }
 
@@ -65,9 +64,8 @@ impl Module {
     ) -> Option<(HirFileId, TreeArc<ast::Module>)> {
         let def_map = db.crate_def_map(self.krate);
         let decl = def_map[self.module_id].declaration?;
-        let syntax_node = db.file_item(decl);
-        let ast = ast::Module::cast(&syntax_node).unwrap().to_owned();
-        Some((decl.file_id, ast))
+        let ast = decl.to_node(db);
+        Some((decl.file_id(), ast))
     }
 
     pub(crate) fn import_source_impl(
diff --git a/crates/ra_hir/src/db.rs b/crates/ra_hir/src/db.rs
index 3296b9b31..147005848 100644
--- a/crates/ra_hir/src/db.rs
+++ b/crates/ra_hir/src/db.rs
@@ -4,7 +4,7 @@ use ra_syntax::{SyntaxNode, TreeArc, SourceFile};
 use ra_db::{SourceDatabase, salsa};
 
 use crate::{
-    HirFileId, MacroDefId, SourceFileItems, SourceItemId, Crate, Module, HirInterner,
+    HirFileId, MacroDefId, AstIdMap, ErasedFileAstId, Crate, Module, HirInterner,
     Function, FnSignature, ExprScopes, TypeAlias,
     Struct, Enum, StructField,
     Const, ConstSignature, Static,
@@ -22,7 +22,7 @@ pub trait DefDatabase: SourceDatabase + AsRef<HirInterner> {
     #[salsa::invoke(crate::ids::macro_def_query)]
     fn macro_def(&self, macro_id: MacroDefId) -> Option<Arc<mbe::MacroRules>>;
 
-    #[salsa::invoke(HirFileId::hir_parse)]
+    #[salsa::invoke(HirFileId::hir_parse_query)]
     fn hir_parse(&self, file_id: HirFileId) -> TreeArc<SourceFile>;
 
     #[salsa::invoke(crate::adt::StructData::struct_data_query)]
@@ -34,11 +34,11 @@ pub trait DefDatabase: SourceDatabase + AsRef<HirInterner> {
     #[salsa::invoke(crate::traits::TraitData::trait_data_query)]
     fn trait_data(&self, t: Trait) -> Arc<TraitData>;
 
-    #[salsa::invoke(crate::source_id::SourceFileItems::file_items_query)]
-    fn file_items(&self, file_id: HirFileId) -> Arc<SourceFileItems>;
+    #[salsa::invoke(crate::source_id::AstIdMap::ast_id_map_query)]
+    fn ast_id_map(&self, file_id: HirFileId) -> Arc<AstIdMap>;
 
-    #[salsa::invoke(crate::source_id::SourceFileItems::file_item_query)]
-    fn file_item(&self, source_item_id: SourceItemId) -> TreeArc<SyntaxNode>;
+    #[salsa::invoke(crate::source_id::AstIdMap::file_item_query)]
+    fn ast_id_to_node(&self, file_id: HirFileId, ast_id: ErasedFileAstId) -> TreeArc<SyntaxNode>;
 
     #[salsa::invoke(RawItems::raw_items_query)]
     fn raw_items(&self, file_id: HirFileId) -> Arc<RawItems>;
diff --git a/crates/ra_hir/src/ids.rs b/crates/ra_hir/src/ids.rs
index e73dd5d21..eb9939df7 100644
--- a/crates/ra_hir/src/ids.rs
+++ b/crates/ra_hir/src/ids.rs
@@ -1,5 +1,4 @@
 use std::{
-    marker::PhantomData,
     hash::{Hash, Hasher},
     sync::Arc,
 };
@@ -10,7 +9,7 @@ use ra_arena::{RawId, ArenaId, impl_arena_id};
 use mbe::MacroRules;
 
 use crate::{
-    Module, DefDatabase, SourceItemId, SourceFileItemId,
+    Module, DefDatabase, AstId, FileAstId,
 };
 
 #[derive(Debug, Default)]
@@ -22,7 +21,7 @@ pub struct HirInterner {
     consts: LocationInterner<ItemLoc<ast::ConstDef>, ConstId>,
     statics: LocationInterner<ItemLoc<ast::StaticDef>, StaticId>,
     traits: LocationInterner<ItemLoc<ast::TraitDef>, TraitId>,
-    types: LocationInterner<ItemLoc<ast::TypeAliasDef>, TypeId>,
+    types: LocationInterner<ItemLoc<ast::TypeAliasDef>, TypeAliasId>,
 }
 
 impl HirInterner {
@@ -68,7 +67,7 @@ impl HirFileId {
             HirFileIdRepr::File(file_id) => file_id,
             HirFileIdRepr::Macro(macro_call_id) => {
                 let loc = macro_call_id.loc(db);
-                loc.source_item_id.file_id.original_file(db)
+                loc.ast_id.file_id().original_file(db)
             }
         }
     }
@@ -83,7 +82,10 @@ impl HirFileId {
         }
     }
 
-    pub(crate) fn hir_parse(db: &impl DefDatabase, file_id: HirFileId) -> TreeArc<SourceFile> {
+    pub(crate) fn hir_parse_query(
+        db: &impl DefDatabase,
+        file_id: HirFileId,
+    ) -> TreeArc<SourceFile> {
         match file_id.0 {
             HirFileIdRepr::File(file_id) => db.parse(file_id),
             HirFileIdRepr::Macro(macro_call_id) => {
@@ -96,8 +98,7 @@ impl HirFileId {
 
 fn parse_macro(db: &impl DefDatabase, macro_call_id: MacroCallId) -> Option<TreeArc<SourceFile>> {
     let loc = macro_call_id.loc(db);
-    let syntax = db.file_item(loc.source_item_id);
-    let macro_call = ast::MacroCall::cast(&syntax).unwrap();
+    let macro_call = loc.ast_id.to_node(db);
     let (macro_arg, _) = macro_call.token_tree().and_then(mbe::ast_to_token_tree)?;
 
     let macro_rules = db.macro_def(loc.def)?;
@@ -124,15 +125,10 @@ impl From<MacroCallId> for HirFileId {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub enum MacroDefId {
-    MacroByExample { source_item_id: SourceItemId },
-}
+pub struct MacroDefId(pub(crate) AstId<ast::MacroCall>);
 
 pub(crate) fn macro_def_query(db: &impl DefDatabase, id: MacroDefId) -> Option<Arc<MacroRules>> {
-    let syntax_node = match id {
-        MacroDefId::MacroByExample { source_item_id } => db.file_item(source_item_id),
-    };
-    let macro_call = ast::MacroCall::cast(&syntax_node).unwrap();
+    let macro_call = id.0.to_node(db);
     let arg = macro_call.token_tree()?;
     let (tt, _) = mbe::ast_to_token_tree(arg)?;
     let rules = MacroRules::parse(&tt).ok()?;
@@ -148,7 +144,7 @@ impl_arena_id!(MacroCallId);
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct MacroCallLoc {
     pub(crate) def: MacroDefId,
-    pub(crate) source_item_id: SourceItemId,
+    pub(crate) ast_id: AstId<ast::MacroCall>,
 }
 
 impl MacroCallId {
@@ -158,7 +154,6 @@ impl MacroCallId {
 }
 
 impl MacroCallLoc {
-    #[allow(unused)]
     pub(crate) fn id(&self, db: &impl AsRef<HirInterner>) -> MacroCallId {
         db.as_ref().macros.loc2id(&self)
     }
@@ -167,26 +162,25 @@ impl MacroCallLoc {
 #[derive(Debug)]
 pub struct ItemLoc<N: AstNode> {
     pub(crate) module: Module,
-    raw: SourceItemId,
-    _ty: PhantomData<N>,
+    ast_id: AstId<N>,
 }
 
 impl<N: AstNode> PartialEq for ItemLoc<N> {
     fn eq(&self, other: &Self) -> bool {
-        self.module == other.module && self.raw == other.raw
+        self.module == other.module && self.ast_id == other.ast_id
     }
 }
 impl<N: AstNode> Eq for ItemLoc<N> {}
 impl<N: AstNode> Hash for ItemLoc<N> {
     fn hash<H: Hasher>(&self, hasher: &mut H) {
         self.module.hash(hasher);
-        self.raw.hash(hasher);
+        self.ast_id.hash(hasher);
     }
 }
 
 impl<N: AstNode> Clone for ItemLoc<N> {
     fn clone(&self) -> ItemLoc<N> {
-        ItemLoc { module: self.module, raw: self.raw, _ty: PhantomData }
+        ItemLoc { module: self.module, ast_id: self.ast_id }
     }
 }
 
@@ -213,26 +207,19 @@ impl<'a, DB: DefDatabase> LocationCtx<&'a DB> {
 pub(crate) trait AstItemDef<N: AstNode>: ArenaId + Clone {
     fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<N>, Self>;
     fn from_ast(ctx: LocationCtx<&impl DefDatabase>, ast: &N) -> Self {
-        let items = ctx.db.file_items(ctx.file_id);
-        let item_id = items.id_of(ctx.file_id, ast.syntax());
-        Self::from_source_item_id_unchecked(ctx, item_id)
+        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_source_item_id_unchecked(
-        ctx: LocationCtx<&impl DefDatabase>,
-        item_id: SourceFileItemId,
-    ) -> Self {
-        let raw = SourceItemId { file_id: ctx.file_id, item_id };
-        let loc = ItemLoc { module: ctx.module, raw, _ty: PhantomData };
-
+    fn from_ast_id(ctx: LocationCtx<&impl DefDatabase>, ast_id: FileAstId<N>) -> Self {
+        let loc = ItemLoc { module: ctx.module, ast_id: ast_id.with_file_id(ctx.file_id) };
         Self::interner(ctx.db.as_ref()).loc2id(&loc)
     }
     fn source(self, db: &impl DefDatabase) -> (HirFileId, TreeArc<N>) {
         let int = Self::interner(db.as_ref());
         let loc = int.id2loc(self);
-        let syntax = db.file_item(loc.raw);
-        let ast =
-            N::cast(&syntax).unwrap_or_else(|| panic!("invalid ItemLoc: {:?}", loc.raw)).to_owned();
-        (loc.raw.file_id, ast)
+        let ast = loc.ast_id.to_node(db);
+        (loc.ast_id.file_id(), ast)
     }
     fn module(self, db: &impl DefDatabase) -> Module {
         let int = Self::interner(db.as_ref());
@@ -242,7 +229,7 @@ pub(crate) trait AstItemDef<N: AstNode>: ArenaId + Clone {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct FunctionId(RawId);
+pub(crate) struct FunctionId(RawId);
 impl_arena_id!(FunctionId);
 impl AstItemDef<ast::FnDef> for FunctionId {
     fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::FnDef>, Self> {
@@ -251,7 +238,7 @@ impl AstItemDef<ast::FnDef> for FunctionId {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct StructId(RawId);
+pub(crate) struct StructId(RawId);
 impl_arena_id!(StructId);
 impl AstItemDef<ast::StructDef> for StructId {
     fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::StructDef>, Self> {
@@ -260,7 +247,7 @@ impl AstItemDef<ast::StructDef> for StructId {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct EnumId(RawId);
+pub(crate) struct EnumId(RawId);
 impl_arena_id!(EnumId);
 impl AstItemDef<ast::EnumDef> for EnumId {
     fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::EnumDef>, Self> {
@@ -269,7 +256,7 @@ impl AstItemDef<ast::EnumDef> for EnumId {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct ConstId(RawId);
+pub(crate) struct ConstId(RawId);
 impl_arena_id!(ConstId);
 impl AstItemDef<ast::ConstDef> for ConstId {
     fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::ConstDef>, Self> {
@@ -278,7 +265,7 @@ impl AstItemDef<ast::ConstDef> for ConstId {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct StaticId(RawId);
+pub(crate) struct StaticId(RawId);
 impl_arena_id!(StaticId);
 impl AstItemDef<ast::StaticDef> for StaticId {
     fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::StaticDef>, Self> {
@@ -287,7 +274,7 @@ impl AstItemDef<ast::StaticDef> for StaticId {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct TraitId(RawId);
+pub(crate) struct TraitId(RawId);
 impl_arena_id!(TraitId);
 impl AstItemDef<ast::TraitDef> for TraitId {
     fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::TraitDef>, Self> {
@@ -296,9 +283,9 @@ impl AstItemDef<ast::TraitDef> for TraitId {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct TypeId(RawId);
-impl_arena_id!(TypeId);
-impl AstItemDef<ast::TypeAliasDef> for TypeId {
+pub(crate) struct TypeAliasId(RawId);
+impl_arena_id!(TypeAliasId);
+impl AstItemDef<ast::TypeAliasDef> for TypeAliasId {
     fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::TypeAliasDef>, Self> {
         &interner.types
     }
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index ac2585de0..7c603bbd3 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -48,13 +48,13 @@ mod marks;
 use crate::{
     db::{HirDatabase, DefDatabase},
     name::{AsName, KnownName},
-    source_id::SourceFileItemId,
+    source_id::{FileAstId, AstId},
 };
 
 pub use self::{
     path::{Path, PathKind},
     name::Name,
-    source_id::{SourceFileItems, SourceItemId},
+    source_id::{AstIdMap, ErasedFileAstId},
     ids::{HirFileId, MacroDefId, MacroCallId, MacroCallLoc, HirInterner},
     nameres::{PerNs, Namespace},
     ty::{Ty, ApplicationTy, TypeCtor, Substs, display::HirDisplay},
diff --git a/crates/ra_hir/src/nameres.rs b/crates/ra_hir/src/nameres.rs
index e962bbd31..67b9d6986 100644
--- a/crates/ra_hir/src/nameres.rs
+++ b/crates/ra_hir/src/nameres.rs
@@ -59,13 +59,15 @@ use rustc_hash::FxHashMap;
 use ra_arena::{Arena, RawId, impl_arena_id};
 use ra_db::{FileId, Edition};
 use test_utils::tested_by;
+use ra_syntax::ast;
 
 use crate::{
-    ModuleDef, Name, Crate, Module, SourceItemId,
+    ModuleDef, Name, Crate, Module,
     DefDatabase, Path, PathKind, HirFileId, Trait,
     ids::MacroDefId,
     diagnostics::DiagnosticSink,
     nameres::diagnostics::DefDiagnostic,
+    AstId,
 };
 
 pub(crate) use self::raw::{RawItems, ImportId, ImportSourceMap};
@@ -106,7 +108,7 @@ pub(crate) struct ModuleData {
     pub(crate) children: FxHashMap<Name, CrateModuleId>,
     pub(crate) scope: ModuleScope,
     /// None for root
-    pub(crate) declaration: Option<SourceItemId>,
+    pub(crate) declaration: Option<AstId<ast::Module>>,
     /// None for inline modules.
     ///
     /// Note that non-inline modules, by definition, live inside non-macro file.
@@ -225,7 +227,7 @@ impl CrateDefMap {
     pub(crate) fn find_module_by_source(
         &self,
         file_id: HirFileId,
-        decl_id: Option<SourceItemId>,
+        decl_id: Option<AstId<ast::Module>>,
     ) -> Option<CrateModuleId> {
         let (module_id, _module_data) = self.modules.iter().find(|(_module_id, module_data)| {
             if decl_id.is_some() {
@@ -429,10 +431,10 @@ impl CrateDefMap {
 
 mod diagnostics {
     use relative_path::RelativePathBuf;
-    use ra_syntax::{AstPtr, AstNode, ast};
+    use ra_syntax::{AstPtr, ast};
 
     use crate::{
-        SourceItemId, DefDatabase,
+        AstId, DefDatabase,
         nameres::CrateModuleId,
         diagnostics::{DiagnosticSink, UnresolvedModule},
 };
@@ -441,7 +443,7 @@ mod diagnostics {
     pub(super) enum DefDiagnostic {
         UnresolvedModule {
             module: CrateModuleId,
-            declaration: SourceItemId,
+            declaration: AstId<ast::Module>,
             candidate: RelativePathBuf,
         },
     }
@@ -458,10 +460,9 @@ mod diagnostics {
                     if *module != target_module {
                         return;
                     }
-                    let syntax = db.file_item(*declaration);
-                    let decl = ast::Module::cast(&syntax).unwrap();
+                    let decl = declaration.to_node(db);
                     sink.push(UnresolvedModule {
-                        file: declaration.file_id,
+                        file: declaration.file_id(),
                         decl: AstPtr::new(&decl),
                         candidate: candidate.clone(),
                     })
@@ -469,5 +470,4 @@ mod diagnostics {
             }
         }
     }
-
 }
diff --git a/crates/ra_hir/src/nameres/collector.rs b/crates/ra_hir/src/nameres/collector.rs
index 4fb298155..39cadc94a 100644
--- a/crates/ra_hir/src/nameres/collector.rs
+++ b/crates/ra_hir/src/nameres/collector.rs
@@ -3,10 +3,11 @@ use rustc_hash::FxHashMap;
 use relative_path::RelativePathBuf;
 use test_utils::tested_by;
 use ra_db::FileId;
+use ra_syntax::ast;
 
 use crate::{
     Function, Module, Struct, Enum, Const, Static, Trait, TypeAlias,
-    DefDatabase, HirFileId, Name, Path, SourceItemId,
+    DefDatabase, HirFileId, Name, Path,
     KnownName,
     nameres::{
         Resolution, PerNs, ModuleDef, ReachedFixedPoint, ResolveMode,
@@ -15,6 +16,7 @@ use crate::{
         raw,
     },
     ids::{AstItemDef, LocationCtx, MacroCallLoc, MacroCallId, MacroDefId},
+    AstId,
 };
 
 pub(super) fn collect_defs(db: &impl DefDatabase, mut def_map: CrateDefMap) -> CrateDefMap {
@@ -51,7 +53,7 @@ struct DefCollector<DB> {
     def_map: CrateDefMap,
     glob_imports: FxHashMap<CrateModuleId, Vec<(CrateModuleId, raw::ImportId)>>,
     unresolved_imports: Vec<(CrateModuleId, raw::ImportId, raw::ImportData)>,
-    unexpanded_macros: Vec<(CrateModuleId, SourceItemId, Path)>,
+    unexpanded_macros: Vec<(CrateModuleId, AstId<ast::MacroCall>, Path)>,
     global_macro_scope: FxHashMap<Name, MacroDefId>,
 }
 
@@ -293,7 +295,7 @@ where
         let mut macros = std::mem::replace(&mut self.unexpanded_macros, Vec::new());
         let mut resolved = Vec::new();
         let mut res = ReachedFixedPoint::Yes;
-        macros.retain(|(module_id, source_item_id, path)| {
+        macros.retain(|(module_id, ast_id, path)| {
             if path.segments.len() != 2 {
                 return true;
             }
@@ -309,8 +311,7 @@ where
             res = ReachedFixedPoint::No;
             let def_map = self.db.crate_def_map(krate);
             if let Some(macro_id) = def_map.public_macros.get(&path.segments[1].name).cloned() {
-                let call_id =
-                    MacroCallLoc { def: macro_id, source_item_id: *source_item_id }.id(self.db);
+                let call_id = MacroCallLoc { def: macro_id, ast_id: *ast_id }.id(self.db);
                 resolved.push((*module_id, call_id));
             }
             false
@@ -364,12 +365,9 @@ where
     fn collect_module(&mut self, module: &raw::ModuleData) {
         match module {
             // inline module, just recurse
-            raw::ModuleData::Definition { name, items, source_item_id } => {
-                let module_id = self.push_child_module(
-                    name.clone(),
-                    source_item_id.with_file_id(self.file_id),
-                    None,
-                );
+            raw::ModuleData::Definition { name, items, ast_id } => {
+                let module_id =
+                    self.push_child_module(name.clone(), ast_id.with_file_id(self.file_id), None);
                 ModCollector {
                     def_collector: &mut *self.def_collector,
                     module_id,
@@ -379,13 +377,12 @@ where
                 .collect(&*items);
             }
             // out of line module, resovle, parse and recurse
-            raw::ModuleData::Declaration { name, source_item_id } => {
-                let source_item_id = source_item_id.with_file_id(self.file_id);
+            raw::ModuleData::Declaration { name, ast_id } => {
+                let ast_id = ast_id.with_file_id(self.file_id);
                 let is_root = self.def_collector.def_map.modules[self.module_id].parent.is_none();
                 match resolve_submodule(self.def_collector.db, self.file_id, name, is_root) {
                     Ok(file_id) => {
-                        let module_id =
-                            self.push_child_module(name.clone(), source_item_id, Some(file_id));
+                        let module_id = self.push_child_module(name.clone(), ast_id, Some(file_id));
                         let raw_items = self.def_collector.db.raw_items(file_id.into());
                         ModCollector {
                             def_collector: &mut *self.def_collector,
@@ -398,7 +395,7 @@ where
                     Err(candidate) => self.def_collector.def_map.diagnostics.push(
                         DefDiagnostic::UnresolvedModule {
                             module: self.module_id,
-                            declaration: source_item_id,
+                            declaration: ast_id,
                             candidate,
                         },
                     ),
@@ -410,7 +407,7 @@ where
     fn push_child_module(
         &mut self,
         name: Name,
-        declaration: SourceItemId,
+        declaration: AstId<ast::Module>,
         definition: Option<FileId>,
     ) -> CrateModuleId {
         let modules = &mut self.def_collector.def_map.modules;
@@ -432,23 +429,24 @@ where
     fn define_def(&mut self, def: &raw::DefData) {
         let module = Module { krate: self.def_collector.def_map.krate, module_id: self.module_id };
         let ctx = LocationCtx::new(self.def_collector.db, module, self.file_id.into());
-        macro_rules! id {
-            () => {
-                AstItemDef::from_source_item_id_unchecked(ctx, def.source_item_id)
+
+        macro_rules! def {
+            ($kind:ident, $ast_id:ident) => {
+                $kind { id: AstItemDef::from_ast_id(ctx, $ast_id) }.into()
             };
         }
         let name = def.name.clone();
         let def: PerNs<ModuleDef> = match def.kind {
-            raw::DefKind::Function => PerNs::values(Function { id: id!() }.into()),
-            raw::DefKind::Struct => {
-                let s = Struct { id: id!() }.into();
+            raw::DefKind::Function(ast_id) => PerNs::values(def!(Function, ast_id)),
+            raw::DefKind::Struct(ast_id) => {
+                let s = def!(Struct, ast_id);
                 PerNs::both(s, s)
             }
-            raw::DefKind::Enum => PerNs::types(Enum { id: id!() }.into()),
-            raw::DefKind::Const => PerNs::values(Const { id: id!() }.into()),
-            raw::DefKind::Static => PerNs::values(Static { id: id!() }.into()),
-            raw::DefKind::Trait => PerNs::types(Trait { id: id!() }.into()),
-            raw::DefKind::TypeAlias => PerNs::types(TypeAlias { id: id!() }.into()),
+            raw::DefKind::Enum(ast_id) => PerNs::types(def!(Enum, ast_id)),
+            raw::DefKind::Const(ast_id) => PerNs::values(def!(Const, ast_id)),
+            raw::DefKind::Static(ast_id) => PerNs::values(def!(Static, ast_id)),
+            raw::DefKind::Trait(ast_id) => PerNs::types(def!(Trait, ast_id)),
+            raw::DefKind::TypeAlias(ast_id) => PerNs::types(def!(TypeAlias, ast_id)),
         };
         let resolution = Resolution { def, import: None };
         self.def_collector.update(self.module_id, None, &[(name, resolution)])
@@ -458,34 +456,27 @@ where
         // Case 1: macro rules, define a macro in crate-global mutable scope
         if is_macro_rules(&mac.path) {
             if let Some(name) = &mac.name {
-                let macro_id = MacroDefId::MacroByExample {
-                    source_item_id: mac.source_item_id.with_file_id(self.file_id),
-                };
+                let macro_id = MacroDefId(mac.ast_id.with_file_id(self.file_id));
                 self.def_collector.define_macro(name.clone(), macro_id, mac.export)
             }
             return;
         }
 
-        let source_item_id = SourceItemId { file_id: self.file_id, item_id: mac.source_item_id };
+        let ast_id = mac.ast_id.with_file_id(self.file_id);
 
         // Case 2: try to expand macro_rules from this crate, triggering
         // recursive item collection.
         if let Some(&macro_id) =
             mac.path.as_ident().and_then(|name| self.def_collector.global_macro_scope.get(name))
         {
-            let macro_call_id =
-                MacroCallLoc { def: macro_id, source_item_id }.id(self.def_collector.db);
+            let macro_call_id = MacroCallLoc { def: macro_id, ast_id }.id(self.def_collector.db);
 
             self.def_collector.collect_macro_expansion(self.module_id, macro_call_id);
             return;
         }
 
         // Case 3: path to a macro from another crate, expand during name resolution
-        self.def_collector.unexpanded_macros.push((
-            self.module_id,
-            source_item_id,
-            mac.path.clone(),
-        ))
+        self.def_collector.unexpanded_macros.push((self.module_id, ast_id, mac.path.clone()))
     }
 }
 
diff --git a/crates/ra_hir/src/nameres/raw.rs b/crates/ra_hir/src/nameres/raw.rs
index f32004601..0936229ac 100644
--- a/crates/ra_hir/src/nameres/raw.rs
+++ b/crates/ra_hir/src/nameres/raw.rs
@@ -12,7 +12,7 @@ use ra_syntax::{
 
 use crate::{
     DefDatabase, Name, AsName, Path, HirFileId, ModuleSource,
-    SourceFileItemId, SourceFileItems,
+    AstIdMap, FileAstId,
 };
 
 /// `RawItems` is a set of top-level items in a file (except for impls).
@@ -60,7 +60,7 @@ impl RawItems {
     ) -> (Arc<RawItems>, Arc<ImportSourceMap>) {
         let mut collector = RawItemsCollector {
             raw_items: RawItems::default(),
-            source_file_items: db.file_items(file_id.into()),
+            source_ast_id_map: db.ast_id_map(file_id.into()),
             source_map: ImportSourceMap::default(),
         };
         let source_file = db.hir_parse(file_id);
@@ -115,8 +115,8 @@ impl_arena_id!(Module);
 
 #[derive(Debug, PartialEq, Eq)]
 pub(super) enum ModuleData {
-    Declaration { name: Name, source_item_id: SourceFileItemId },
-    Definition { name: Name, source_item_id: SourceFileItemId, items: Vec<RawItem> },
+    Declaration { name: Name, ast_id: FileAstId<ast::Module> },
+    Definition { name: Name, ast_id: FileAstId<ast::Module>, items: Vec<RawItem> },
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
@@ -138,20 +138,19 @@ impl_arena_id!(Def);
 
 #[derive(Debug, PartialEq, Eq)]
 pub(super) struct DefData {
-    pub(super) source_item_id: SourceFileItemId,
     pub(super) name: Name,
     pub(super) kind: DefKind,
 }
 
 #[derive(Debug, PartialEq, Eq, Clone, Copy)]
 pub(super) enum DefKind {
-    Function,
-    Struct,
-    Enum,
-    Const,
-    Static,
-    Trait,
-    TypeAlias,
+    Function(FileAstId<ast::FnDef>),
+    Struct(FileAstId<ast::StructDef>),
+    Enum(FileAstId<ast::EnumDef>),
+    Const(FileAstId<ast::ConstDef>),
+    Static(FileAstId<ast::StaticDef>),
+    Trait(FileAstId<ast::TraitDef>),
+    TypeAlias(FileAstId<ast::TypeAliasDef>),
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
@@ -160,7 +159,7 @@ impl_arena_id!(Macro);
 
 #[derive(Debug, PartialEq, Eq)]
 pub(super) struct MacroData {
-    pub(super) source_item_id: SourceFileItemId,
+    pub(super) ast_id: FileAstId<ast::MacroCall>,
     pub(super) path: Path,
     pub(super) name: Option<Name>,
     pub(super) export: bool,
@@ -168,7 +167,7 @@ pub(super) struct MacroData {
 
 struct RawItemsCollector {
     raw_items: RawItems,
-    source_file_items: Arc<SourceFileItems>,
+    source_ast_id_map: Arc<AstIdMap>,
     source_map: ImportSourceMap,
 }
 
@@ -200,18 +199,31 @@ impl RawItemsCollector {
                 // impls don't participate in name resolution
                 return;
             }
-            ast::ModuleItemKind::StructDef(it) => (DefKind::Struct, it.name()),
-            ast::ModuleItemKind::EnumDef(it) => (DefKind::Enum, it.name()),
-            ast::ModuleItemKind::FnDef(it) => (DefKind::Function, it.name()),
-            ast::ModuleItemKind::TraitDef(it) => (DefKind::Trait, it.name()),
-            ast::ModuleItemKind::TypeAliasDef(it) => (DefKind::TypeAlias, it.name()),
-            ast::ModuleItemKind::ConstDef(it) => (DefKind::Const, it.name()),
-            ast::ModuleItemKind::StaticDef(it) => (DefKind::Static, it.name()),
+            ast::ModuleItemKind::StructDef(it) => {
+                (DefKind::Struct(self.source_ast_id_map.ast_id(it)), it.name())
+            }
+            ast::ModuleItemKind::EnumDef(it) => {
+                (DefKind::Enum(self.source_ast_id_map.ast_id(it)), it.name())
+            }
+            ast::ModuleItemKind::FnDef(it) => {
+                (DefKind::Function(self.source_ast_id_map.ast_id(it)), it.name())
+            }
+            ast::ModuleItemKind::TraitDef(it) => {
+                (DefKind::Trait(self.source_ast_id_map.ast_id(it)), it.name())
+            }
+            ast::ModuleItemKind::TypeAliasDef(it) => {
+                (DefKind::TypeAlias(self.source_ast_id_map.ast_id(it)), it.name())
+            }
+            ast::ModuleItemKind::ConstDef(it) => {
+                (DefKind::Const(self.source_ast_id_map.ast_id(it)), it.name())
+            }
+            ast::ModuleItemKind::StaticDef(it) => {
+                (DefKind::Static(self.source_ast_id_map.ast_id(it)), it.name())
+            }
         };
         if let Some(name) = name {
             let name = name.as_name();
-            let source_item_id = self.source_file_items.id_of_unchecked(item.syntax());
-            let def = self.raw_items.defs.alloc(DefData { name, kind, source_item_id });
+            let def = self.raw_items.defs.alloc(DefData { name, kind });
             self.push_item(current_module, RawItem::Def(def))
         }
     }
@@ -221,10 +233,9 @@ impl RawItemsCollector {
             Some(it) => it.as_name(),
             None => return,
         };
-        let source_item_id = self.source_file_items.id_of_unchecked(module.syntax());
+        let ast_id = self.source_ast_id_map.ast_id(module);
         if module.has_semi() {
-            let item =
-                self.raw_items.modules.alloc(ModuleData::Declaration { name, source_item_id });
+            let item = self.raw_items.modules.alloc(ModuleData::Declaration { name, ast_id });
             self.push_item(current_module, RawItem::Module(item));
             return;
         }
@@ -232,7 +243,7 @@ impl RawItemsCollector {
         if let Some(item_list) = module.item_list() {
             let item = self.raw_items.modules.alloc(ModuleData::Definition {
                 name,
-                source_item_id,
+                ast_id,
                 items: Vec::new(),
             });
             self.process_module(Some(item), item_list);
@@ -286,9 +297,9 @@ impl RawItemsCollector {
         };
 
         let name = m.name().map(|it| it.as_name());
-        let source_item_id = self.source_file_items.id_of_unchecked(m.syntax());
+        let ast_id = self.source_ast_id_map.ast_id(m);
         let export = m.has_atom_attr("macro_export");
-        let m = self.raw_items.macros.alloc(MacroData { source_item_id, path, name, export });
+        let m = self.raw_items.macros.alloc(MacroData { ast_id, path, name, export });
         self.push_item(current_module, RawItem::Macro(m));
     }
 
diff --git a/crates/ra_hir/src/source_binder.rs b/crates/ra_hir/src/source_binder.rs
index db9e3a22e..9dae4c3d1 100644
--- a/crates/ra_hir/src/source_binder.rs
+++ b/crates/ra_hir/src/source_binder.rs
@@ -13,10 +13,10 @@ use ra_syntax::{
 };
 
 use crate::{
-    HirDatabase, Function, Struct, Enum, SourceItemId,
+    HirDatabase, Function, Struct, Enum,
     AsName, Module, HirFileId, Crate, Trait, Resolver,
     ids::LocationCtx,
-    expr
+    expr, AstId
 };
 
 /// Locates the module by `FileId`. Picks topmost module in the file.
@@ -54,8 +54,8 @@ fn module_from_inline(
 ) -> Option<Module> {
     assert!(!module.has_semi());
     let file_id = file_id.into();
-    let file_items = db.file_items(file_id);
-    let item_id = file_items.id_of(file_id, module.syntax()).with_file_id(file_id);
+    let ast_id_map = db.ast_id_map(file_id);
+    let item_id = ast_id_map.ast_id(module).with_file_id(file_id);
     module_from_source(db, file_id, Some(item_id))
 }
 
@@ -75,7 +75,7 @@ pub fn module_from_child_node(
 fn module_from_source(
     db: &impl HirDatabase,
     file_id: HirFileId,
-    decl_id: Option<SourceItemId>,
+    decl_id: Option<AstId<ast::Module>>,
 ) -> Option<Module> {
     let source_root_id = db.file_source_root(file_id.as_original_file());
     db.source_root_crates(source_root_id).iter().map(|&crate_id| Crate { crate_id }).find_map(
diff --git a/crates/ra_hir/src/source_id.rs b/crates/ra_hir/src/source_id.rs
index 62707ba6a..0a8fb6d32 100644
--- a/crates/ra_hir/src/source_id.rs
+++ b/crates/ra_hir/src/source_id.rs
@@ -1,59 +1,122 @@
-use std::sync::Arc;
+use std::{marker::PhantomData, sync::Arc, hash::{Hash, Hasher}};
 
 use ra_arena::{Arena, RawId, impl_arena_id};
 use ra_syntax::{SyntaxNodePtr, TreeArc, SyntaxNode, SourceFile, AstNode, ast};
 
 use crate::{HirFileId, DefDatabase};
 
-/// Identifier of item within a specific file. This is stable over reparses, so
-/// it's OK to use it as a salsa key/value.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub(crate) struct SourceFileItemId(RawId);
-impl_arena_id!(SourceFileItemId);
+/// `AstId` points to an AST node in any file.
+///
+/// It is stable across reparses, and can be used as salsa key/value.
+#[derive(Debug)]
+pub(crate) struct AstId<N: AstNode> {
+    file_id: HirFileId,
+    file_ast_id: FileAstId<N>,
+}
+
+impl<N: AstNode> Clone for AstId<N> {
+    fn clone(&self) -> AstId<N> {
+        *self
+    }
+}
+impl<N: AstNode> Copy for AstId<N> {}
+
+impl<N: AstNode> PartialEq for AstId<N> {
+    fn eq(&self, other: &Self) -> bool {
+        (self.file_id, self.file_ast_id) == (other.file_id, other.file_ast_id)
+    }
+}
+impl<N: AstNode> Eq for AstId<N> {}
+impl<N: AstNode> Hash for AstId<N> {
+    fn hash<H: Hasher>(&self, hasher: &mut H) {
+        (self.file_id, self.file_ast_id).hash(hasher);
+    }
+}
+
+impl<N: AstNode> AstId<N> {
+    pub(crate) fn file_id(&self) -> HirFileId {
+        self.file_id
+    }
+
+    pub(crate) fn to_node(&self, db: &impl DefDatabase) -> TreeArc<N> {
+        let syntax_node = db.ast_id_to_node(self.file_id, self.file_ast_id.raw);
+        N::cast(&syntax_node).unwrap().to_owned()
+    }
+}
+
+/// `AstId` points to an AST node in a specific file.
+#[derive(Debug)]
+pub(crate) struct FileAstId<N: AstNode> {
+    raw: ErasedFileAstId,
+    _ty: PhantomData<N>,
+}
+
+impl<N: AstNode> Clone for FileAstId<N> {
+    fn clone(&self) -> FileAstId<N> {
+        *self
+    }
+}
+impl<N: AstNode> Copy for FileAstId<N> {}
 
-impl SourceFileItemId {
-    pub(crate) fn with_file_id(self, file_id: HirFileId) -> SourceItemId {
-        SourceItemId { file_id, item_id: self }
+impl<N: AstNode> PartialEq for FileAstId<N> {
+    fn eq(&self, other: &Self) -> bool {
+        self.raw == other.raw
+    }
+}
+impl<N: AstNode> Eq for FileAstId<N> {}
+impl<N: AstNode> Hash for FileAstId<N> {
+    fn hash<H: Hasher>(&self, hasher: &mut H) {
+        self.raw.hash(hasher);
     }
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct SourceItemId {
-    pub(crate) file_id: HirFileId,
-    pub(crate) item_id: SourceFileItemId,
+impl<N: AstNode> FileAstId<N> {
+    pub(crate) fn with_file_id(self, file_id: HirFileId) -> AstId<N> {
+        AstId { file_id, file_ast_id: self }
+    }
 }
 
-/// Maps items' `SyntaxNode`s to `SourceFileItemId`s and back.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ErasedFileAstId(RawId);
+impl_arena_id!(ErasedFileAstId);
+
+/// Maps items' `SyntaxNode`s to `ErasedFileAstId`s and back.
 #[derive(Debug, PartialEq, Eq)]
-pub struct SourceFileItems {
-    file_id: HirFileId,
-    arena: Arena<SourceFileItemId, SyntaxNodePtr>,
+pub struct AstIdMap {
+    arena: Arena<ErasedFileAstId, SyntaxNodePtr>,
 }
 
-impl SourceFileItems {
-    pub(crate) fn file_items_query(
-        db: &impl DefDatabase,
-        file_id: HirFileId,
-    ) -> Arc<SourceFileItems> {
+impl AstIdMap {
+    pub(crate) fn ast_id_map_query(db: &impl DefDatabase, file_id: HirFileId) -> Arc<AstIdMap> {
         let source_file = db.hir_parse(file_id);
-        Arc::new(SourceFileItems::from_source_file(&source_file, file_id))
+        Arc::new(AstIdMap::from_source_file(&source_file))
     }
 
     pub(crate) fn file_item_query(
         db: &impl DefDatabase,
-        source_item_id: SourceItemId,
+        file_id: HirFileId,
+        ast_id: ErasedFileAstId,
     ) -> TreeArc<SyntaxNode> {
-        let source_file = db.hir_parse(source_item_id.file_id);
-        db.file_items(source_item_id.file_id)[source_item_id.item_id]
-            .to_node(&source_file)
-            .to_owned()
+        let source_file = db.hir_parse(file_id);
+        db.ast_id_map(file_id).arena[ast_id].to_node(&source_file).to_owned()
     }
 
-    pub(crate) fn from_source_file(
-        source_file: &SourceFile,
-        file_id: HirFileId,
-    ) -> SourceFileItems {
-        let mut res = SourceFileItems { file_id, arena: Arena::default() };
+    pub(crate) fn ast_id<N: AstNode>(&self, item: &N) -> FileAstId<N> {
+        let ptr = SyntaxNodePtr::new(item.syntax());
+        let raw = match self.arena.iter().find(|(_id, i)| **i == ptr) {
+            Some((it, _)) => it,
+            None => panic!(
+                "Can't find {:?} in AstIdMap:\n{:?}",
+                item.syntax(),
+                self.arena.iter().map(|(_id, i)| i).collect::<Vec<_>>(),
+            ),
+        };
+
+        FileAstId { raw, _ty: PhantomData }
+    }
+
+    fn from_source_file(source_file: &SourceFile) -> AstIdMap {
+        let mut res = AstIdMap { arena: Arena::default() };
         // By walking the tree in bread-first order we make sure that parents
         // get lower ids then children. That is, adding a new child does not
         // change parent's id. This means that, say, adding a new function to a
@@ -68,35 +131,9 @@ impl SourceFileItems {
         res
     }
 
-    fn alloc(&mut self, item: &SyntaxNode) -> SourceFileItemId {
+    fn alloc(&mut self, item: &SyntaxNode) -> ErasedFileAstId {
         self.arena.alloc(SyntaxNodePtr::new(item))
     }
-    pub(crate) fn id_of(&self, file_id: HirFileId, item: &SyntaxNode) -> SourceFileItemId {
-        assert_eq!(
-            self.file_id, file_id,
-            "SourceFileItems: wrong file, expected {:?}, got {:?}",
-            self.file_id, file_id
-        );
-        self.id_of_unchecked(item)
-    }
-    pub(crate) fn id_of_unchecked(&self, item: &SyntaxNode) -> SourceFileItemId {
-        let ptr = SyntaxNodePtr::new(item);
-        if let Some((id, _)) = self.arena.iter().find(|(_id, i)| **i == ptr) {
-            return id;
-        }
-        panic!(
-            "Can't find {:?} in SourceFileItems:\n{:?}",
-            item,
-            self.arena.iter().map(|(_id, i)| i).collect::<Vec<_>>(),
-        );
-    }
-}
-
-impl std::ops::Index<SourceFileItemId> for SourceFileItems {
-    type Output = SyntaxNodePtr;
-    fn index(&self, idx: SourceFileItemId) -> &SyntaxNodePtr {
-        &self.arena[idx]
-    }
 }
 
 /// Walks the subtree in bfs order, calling `f` for each node.