21 files changed, 147 insertions, 106 deletions

diff --git a/crates/ra_hir/src/adt.rs b/crates/ra_hir/src/adt.rs
index 22bbad964..c549e2126 100644
--- a/crates/ra_hir/src/adt.rs
+++ b/crates/ra_hir/src/adt.rs
@@ -12,7 +12,7 @@ use ra_syntax::{
 use crate::{
     Name, AsName, Struct, Enum, EnumVariant, Crate,
     HirDatabase, HirFileId, StructField, FieldSource,
-    type_ref::TypeRef,
+    type_ref::TypeRef, PersistentHirDatabase,
 };
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
@@ -33,7 +33,7 @@ impl AdtDef {
 }
 
 impl Struct {
-    pub(crate) fn variant_data(&self, db: &impl HirDatabase) -> Arc<VariantData> {
+    pub(crate) fn variant_data(&self, db: &impl PersistentHirDatabase) -> Arc<VariantData> {
         db.struct_data((*self).into()).variant_data.clone()
     }
 }
@@ -52,7 +52,10 @@ impl StructData {
         StructData { name, variant_data }
     }
 
-    pub(crate) fn struct_data_query(db: &impl HirDatabase, struct_: Struct) -> Arc<StructData> {
+    pub(crate) fn struct_data_query(
+        db: &impl PersistentHirDatabase,
+        struct_: Struct,
+    ) -> Arc<StructData> {
         let (_, struct_def) = struct_.source(db);
         Arc::new(StructData::new(&*struct_def))
     }
@@ -68,7 +71,7 @@ fn variants(enum_def: &ast::EnumDef) -> impl Iterator<Item = &ast::EnumVariant>
 impl EnumVariant {
     pub(crate) fn source_impl(
         &self,
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
     ) -> (HirFileId, TreeArc<ast::EnumVariant>) {
         let (file_id, enum_def) = self.parent.source(db);
         let var = variants(&*enum_def)
@@ -79,7 +82,7 @@ impl EnumVariant {
             .to_owned();
         (file_id, var)
     }
-    pub(crate) fn variant_data(&self, db: &impl HirDatabase) -> Arc<VariantData> {
+    pub(crate) fn variant_data(&self, db: &impl PersistentHirDatabase) -> Arc<VariantData> {
         db.enum_data(self.parent).variants[self.id]
             .variant_data
             .clone()
@@ -93,7 +96,7 @@ pub struct EnumData {
 }
 
 impl EnumData {
-    pub(crate) fn enum_data_query(db: &impl HirDatabase, e: Enum) -> Arc<EnumData> {
+    pub(crate) fn enum_data_query(db: &impl PersistentHirDatabase, e: Enum) -> Arc<EnumData> {
         let (_file_id, enum_def) = e.source(db);
         let name = enum_def.name().map(|n| n.as_name());
         let variants = variants(&*enum_def)
@@ -191,7 +194,7 @@ impl VariantDef {
             VariantDef::EnumVariant(it) => it.field(db, name),
         }
     }
-    pub(crate) fn variant_data(self, db: &impl HirDatabase) -> Arc<VariantData> {
+    pub(crate) fn variant_data(self, db: &impl PersistentHirDatabase) -> Arc<VariantData> {
         match self {
             VariantDef::Struct(it) => it.variant_data(db),
             VariantDef::EnumVariant(it) => it.variant_data(db),
@@ -200,7 +203,7 @@ impl VariantDef {
 }
 
 impl StructField {
-    pub(crate) fn source_impl(&self, db: &impl HirDatabase) -> (HirFileId, FieldSource) {
+    pub(crate) fn source_impl(&self, db: &impl PersistentHirDatabase) -> (HirFileId, FieldSource) {
         let var_data = self.parent.variant_data(db);
         let fields = var_data.fields().unwrap();
         let ss;
diff --git a/crates/ra_hir/src/code_model_api.rs b/crates/ra_hir/src/code_model_api.rs
index 9405aa8ad..71123a698 100644
--- a/crates/ra_hir/src/code_model_api.rs
+++ b/crates/ra_hir/src/code_model_api.rs
@@ -8,7 +8,7 @@ use crate::{
     Name, Path, PerNs, ScopesWithSyntaxMapping, Ty, HirFileId,
     type_ref::TypeRef,
     nameres::{ModuleScope, lower::ImportId},
-    db::HirDatabase,
+    HirDatabase, PersistentHirDatabase,
     expr::BodySyntaxMapping,
     ty::{InferenceResult},
     adt::{EnumVariantId, StructFieldId, VariantDef},
@@ -37,10 +37,10 @@ impl Crate {
     pub fn crate_id(&self) -> CrateId {
         self.crate_id
     }
-    pub fn dependencies(&self, db: &impl HirDatabase) -> Vec<CrateDependency> {
+    pub fn dependencies(&self, db: &impl PersistentHirDatabase) -> Vec<CrateDependency> {
         self.dependencies_impl(db)
     }
-    pub fn root_module(&self, db: &impl HirDatabase) -> Option<Module> {
+    pub fn root_module(&self, db: &impl PersistentHirDatabase) -> Option<Module> {
         self.root_module_impl(db)
     }
 }
@@ -105,7 +105,7 @@ impl Module {
     }
 
     /// Returns a node which defines this module. That is, a file or a `mod foo {}` with items.
-    pub fn definition_source(&self, db: &impl HirDatabase) -> (FileId, ModuleSource) {
+    pub fn definition_source(&self, db: &impl PersistentHirDatabase) -> (FileId, ModuleSource) {
         self.definition_source_impl(db)
     }
 
@@ -140,7 +140,7 @@ impl Module {
     /// Topmost parent of this module. Every module has a `crate_root`, but some
     /// might be missing `krate`. This can happen if a module's file is not included
     /// in the module tree of any target in Cargo.toml.
-    pub fn crate_root(&self, db: &impl HirDatabase) -> Module {
+    pub fn crate_root(&self, db: &impl PersistentHirDatabase) -> Module {
         self.crate_root_impl(db)
     }
 
@@ -150,12 +150,12 @@ impl Module {
     }
 
     /// Iterates over all child modules.
-    pub fn children(&self, db: &impl HirDatabase) -> impl Iterator<Item = Module> {
+    pub fn children(&self, db: &impl PersistentHirDatabase) -> impl Iterator<Item = Module> {
         self.children_impl(db)
     }
 
     /// Finds a parent module.
-    pub fn parent(&self, db: &impl HirDatabase) -> Option<Module> {
+    pub fn parent(&self, db: &impl PersistentHirDatabase) -> Option<Module> {
         self.parent_impl(db)
     }
 
@@ -174,7 +174,7 @@ impl Module {
         db.item_map(self.krate)[self.module_id].clone()
     }
 
-    pub fn resolve_path(&self, db: &impl HirDatabase, path: &Path) -> PerNs<ModuleDef> {
+    pub fn resolve_path(&self, db: &impl PersistentHirDatabase, path: &Path) -> PerNs<ModuleDef> {
         db.item_map(self.krate).resolve_path(db, *self, path)
     }
 
@@ -209,7 +209,7 @@ impl StructField {
             .clone()
     }
 
-    pub fn source(&self, db: &impl HirDatabase) -> (HirFileId, FieldSource) {
+    pub fn source(&self, db: &impl PersistentHirDatabase) -> (HirFileId, FieldSource) {
         self.source_impl(db)
     }
 
@@ -237,7 +237,7 @@ pub struct Struct {
 }
 
 impl Struct {
-    pub fn source(&self, db: &impl HirDatabase) -> (HirFileId, TreeArc<ast::StructDef>) {
+    pub fn source(&self, db: &impl PersistentHirDatabase) -> (HirFileId, TreeArc<ast::StructDef>) {
         self.id.source(db)
     }
 
@@ -275,7 +275,7 @@ impl Struct {
             })
     }
 
-    pub fn generic_params(&self, db: &impl HirDatabase) -> Arc<GenericParams> {
+    pub fn generic_params(&self, db: &impl PersistentHirDatabase) -> Arc<GenericParams> {
         db.generic_params((*self).into())
     }
 
@@ -296,7 +296,7 @@ pub struct Enum {
 }
 
 impl Enum {
-    pub fn source(&self, db: &impl HirDatabase) -> (HirFileId, TreeArc<ast::EnumDef>) {
+    pub fn source(&self, db: &impl PersistentHirDatabase) -> (HirFileId, TreeArc<ast::EnumDef>) {
         self.id.source(db)
     }
 
@@ -316,7 +316,7 @@ impl Enum {
             .collect()
     }
 
-    pub fn variant(&self, db: &impl HirDatabase, name: &Name) -> Option<EnumVariant> {
+    pub fn variant(&self, db: &impl PersistentHirDatabase, name: &Name) -> Option<EnumVariant> {
         db.enum_data(*self)
             .variants
             .iter()
@@ -324,7 +324,7 @@ impl Enum {
             .map(|(id, _)| EnumVariant { parent: *self, id })
     }
 
-    pub fn generic_params(&self, db: &impl HirDatabase) -> Arc<GenericParams> {
+    pub fn generic_params(&self, db: &impl PersistentHirDatabase) -> Arc<GenericParams> {
         db.generic_params((*self).into())
     }
 
@@ -346,13 +346,16 @@ pub struct EnumVariant {
 }
 
 impl EnumVariant {
-    pub fn source(&self, db: &impl HirDatabase) -> (HirFileId, TreeArc<ast::EnumVariant>) {
+    pub fn source(
+        &self,
+        db: &impl PersistentHirDatabase,
+    ) -> (HirFileId, TreeArc<ast::EnumVariant>) {
         self.source_impl(db)
     }
     pub fn module(&self, db: &impl HirDatabase) -> Module {
         self.parent.module(db)
     }
-    pub fn parent_enum(&self, _db: &impl HirDatabase) -> Enum {
+    pub fn parent_enum(&self, _db: &impl PersistentHirDatabase) -> Enum {
         self.parent
     }
 
@@ -430,7 +433,7 @@ impl FnSignature {
 }
 
 impl Function {
-    pub fn source(&self, db: &impl HirDatabase) -> (HirFileId, TreeArc<ast::FnDef>) {
+    pub fn source(&self, db: &impl PersistentHirDatabase) -> (HirFileId, TreeArc<ast::FnDef>) {
         self.id.source(db)
     }
 
@@ -463,7 +466,7 @@ impl Function {
         db.infer(*self)
     }
 
-    pub fn generic_params(&self, db: &impl HirDatabase) -> Arc<GenericParams> {
+    pub fn generic_params(&self, db: &impl PersistentHirDatabase) -> Arc<GenericParams> {
         db.generic_params((*self).into())
     }
 }
@@ -480,7 +483,7 @@ pub struct Const {
 }
 
 impl Const {
-    pub fn source(&self, db: &impl HirDatabase) -> (HirFileId, TreeArc<ast::ConstDef>) {
+    pub fn source(&self, db: &impl PersistentHirDatabase) -> (HirFileId, TreeArc<ast::ConstDef>) {
         self.id.source(db)
     }
 }
@@ -497,7 +500,7 @@ pub struct Static {
 }
 
 impl Static {
-    pub fn source(&self, db: &impl HirDatabase) -> (HirFileId, TreeArc<ast::StaticDef>) {
+    pub fn source(&self, db: &impl PersistentHirDatabase) -> (HirFileId, TreeArc<ast::StaticDef>) {
         self.id.source(db)
     }
 }
@@ -514,11 +517,11 @@ pub struct Trait {
 }
 
 impl Trait {
-    pub fn source(&self, db: &impl HirDatabase) -> (HirFileId, TreeArc<ast::TraitDef>) {
+    pub fn source(&self, db: &impl PersistentHirDatabase) -> (HirFileId, TreeArc<ast::TraitDef>) {
         self.id.source(db)
     }
 
-    pub fn generic_params(&self, db: &impl HirDatabase) -> Arc<GenericParams> {
+    pub fn generic_params(&self, db: &impl PersistentHirDatabase) -> Arc<GenericParams> {
         db.generic_params((*self).into())
     }
 }
@@ -535,11 +538,11 @@ pub struct Type {
 }
 
 impl Type {
-    pub fn source(&self, db: &impl HirDatabase) -> (HirFileId, TreeArc<ast::TypeDef>) {
+    pub fn source(&self, db: &impl PersistentHirDatabase) -> (HirFileId, TreeArc<ast::TypeDef>) {
         self.id.source(db)
     }
 
-    pub fn generic_params(&self, db: &impl HirDatabase) -> Arc<GenericParams> {
+    pub fn generic_params(&self, db: &impl PersistentHirDatabase) -> Arc<GenericParams> {
         db.generic_params((*self).into())
     }
 }
diff --git a/crates/ra_hir/src/code_model_impl/function.rs b/crates/ra_hir/src/code_model_impl/function.rs
index 422643996..5b0b31b1d 100644
--- a/crates/ra_hir/src/code_model_impl/function.rs
+++ b/crates/ra_hir/src/code_model_impl/function.rs
@@ -5,7 +5,7 @@ use ra_syntax::ast::{self, NameOwner};
 use crate::{
     HirDatabase, Name, AsName, Function, FnSignature,
     type_ref::{TypeRef, Mutability},
-    expr::Body,
+    expr::Body, PersistentHirDatabase,
     impl_block::ImplBlock,
 };
 
@@ -22,7 +22,10 @@ impl Function {
 }
 
 impl FnSignature {
-    pub(crate) fn fn_signature_query(db: &impl HirDatabase, func: Function) -> Arc<FnSignature> {
+    pub(crate) fn fn_signature_query(
+        db: &impl PersistentHirDatabase,
+        func: Function,
+    ) -> Arc<FnSignature> {
         let (_, node) = func.source(db);
         let name = node
             .name()
diff --git a/crates/ra_hir/src/code_model_impl/krate.rs b/crates/ra_hir/src/code_model_impl/krate.rs
index 86f29d959..1517434b8 100644
--- a/crates/ra_hir/src/code_model_impl/krate.rs
+++ b/crates/ra_hir/src/code_model_impl/krate.rs
@@ -1,10 +1,12 @@
 use crate::{
-    Crate, CrateDependency, AsName, Module,
-    db::HirDatabase,
+    Crate, CrateDependency, AsName, Module, PersistentHirDatabase,
 };
 
 impl Crate {
-    pub(crate) fn dependencies_impl(&self, db: &impl HirDatabase) -> Vec<CrateDependency> {
+    pub(crate) fn dependencies_impl(
+        &self,
+        db: &impl PersistentHirDatabase,
+    ) -> Vec<CrateDependency> {
         let crate_graph = db.crate_graph();
         crate_graph
             .dependencies(self.crate_id)
@@ -17,7 +19,7 @@ impl Crate {
             })
             .collect()
     }
-    pub(crate) fn root_module_impl(&self, db: &impl HirDatabase) -> Option<Module> {
+    pub(crate) fn root_module_impl(&self, db: &impl PersistentHirDatabase) -> Option<Module> {
         let module_tree = db.module_tree(*self);
         let module_id = module_tree.modules().next()?;
 
diff --git a/crates/ra_hir/src/code_model_impl/module.rs b/crates/ra_hir/src/code_model_impl/module.rs
index 4a3901b8b..f487b8532 100644
--- a/crates/ra_hir/src/code_model_impl/module.rs
+++ b/crates/ra_hir/src/code_model_impl/module.rs
@@ -7,7 +7,7 @@ use crate::{
     module_tree::ModuleId,
     impl_block::ImplId,
     nameres::{lower::ImportId},
-    db::HirDatabase,
+    HirDatabase, PersistentHirDatabase,
 };
 
 impl Module {
@@ -24,7 +24,10 @@ impl Module {
         Some(link.name(&module_tree).clone())
     }
 
-    pub(crate) fn definition_source_impl(&self, db: &impl HirDatabase) -> (FileId, ModuleSource) {
+    pub(crate) fn definition_source_impl(
+        &self,
+        db: &impl PersistentHirDatabase,
+    ) -> (FileId, ModuleSource) {
         let module_tree = db.module_tree(self.krate);
         let file_id = self.module_id.file_id(&module_tree);
         let decl_id = self.module_id.decl_id(&module_tree);
@@ -67,7 +70,7 @@ impl Module {
         source_map.get(&source, impl_id)
     }
 
-    pub(crate) fn crate_root_impl(&self, db: &impl HirDatabase) -> Module {
+    pub(crate) fn crate_root_impl(&self, db: &impl PersistentHirDatabase) -> Module {
         let module_tree = db.module_tree(self.krate);
         let module_id = self.module_id.crate_root(&module_tree);
         self.with_module_id(module_id)
@@ -81,7 +84,10 @@ impl Module {
     }
 
     /// Iterates over all child modules.
-    pub(crate) fn children_impl(&self, db: &impl HirDatabase) -> impl Iterator<Item = Module> {
+    pub(crate) fn children_impl(
+        &self,
+        db: &impl PersistentHirDatabase,
+    ) -> impl Iterator<Item = Module> {
         let module_tree = db.module_tree(self.krate);
         let children = self
             .module_id
@@ -91,7 +97,7 @@ impl Module {
         children.into_iter()
     }
 
-    pub(crate) fn parent_impl(&self, db: &impl HirDatabase) -> Option<Module> {
+    pub(crate) fn parent_impl(&self, db: &impl PersistentHirDatabase) -> Option<Module> {
         let module_tree = db.module_tree(self.krate);
         let parent_id = self.module_id.parent(&module_tree)?;
         Some(self.with_module_id(parent_id))
diff --git a/crates/ra_hir/src/db.rs b/crates/ra_hir/src/db.rs
index 7183b1630..6b21fe744 100644
--- a/crates/ra_hir/src/db.rs
+++ b/crates/ra_hir/src/db.rs
@@ -27,9 +27,6 @@ pub trait PersistentHirDatabase: SourceDatabase + AsRef<HirInterner> {
     #[salsa::invoke(crate::macros::expand_macro_invocation)]
     fn expand_macro_invocation(&self, invoc: MacroCallId) -> Option<Arc<MacroExpansion>>;
 
-    #[salsa::invoke(ExprScopes::expr_scopes_query)]
-    fn expr_scopes(&self, func: Function) -> Arc<ExprScopes>;
-
     #[salsa::invoke(crate::adt::StructData::struct_data_query)]
     fn struct_data(&self, s: Struct) -> Arc<StructData>;
 
@@ -39,6 +36,9 @@ pub trait PersistentHirDatabase: SourceDatabase + AsRef<HirInterner> {
     #[salsa::invoke(query_definitions::file_items)]
     fn file_items(&self, file_id: HirFileId) -> Arc<SourceFileItems>;
 
+    #[salsa::invoke(query_definitions::file_item)]
+    fn file_item(&self, source_item_id: SourceItemId) -> TreeArc<SyntaxNode>;
+
     #[salsa::invoke(crate::module_tree::Submodule::submodules_query)]
     fn submodules(
         &self,
@@ -61,20 +61,17 @@ pub trait PersistentHirDatabase: SourceDatabase + AsRef<HirInterner> {
     #[salsa::invoke(crate::module_tree::ModuleTree::module_tree_query)]
     fn module_tree(&self, krate: Crate) -> Arc<ModuleTree>;
 
-    #[salsa::invoke(crate::impl_block::impls_in_module_with_source_map_query)]
-    fn impls_in_module_with_source_map(
-        &self,
-        module: Module,
-    ) -> (Arc<ModuleImplBlocks>, Arc<ImplSourceMap>);
-
     #[salsa::invoke(crate::impl_block::impls_in_module)]
     fn impls_in_module(&self, module: Module) -> Arc<ModuleImplBlocks>;
 
     #[salsa::invoke(crate::impl_block::impls_in_module_source_map_query)]
     fn impls_in_module_source_map(&self, module: Module) -> Arc<ImplSourceMap>;
 
-    #[salsa::invoke(crate::ty::method_resolution::CrateImplBlocks::impls_in_crate_query)]
-    fn impls_in_crate(&self, krate: Crate) -> Arc<CrateImplBlocks>;
+    #[salsa::invoke(crate::impl_block::impls_in_module_with_source_map_query)]
+    fn impls_in_module_with_source_map(
+        &self,
+        module: Module,
+    ) -> (Arc<ModuleImplBlocks>, Arc<ImplSourceMap>);
 
     #[salsa::invoke(crate::generics::GenericParams::generic_params_query)]
     fn generic_params(&self, def: GenericDef) -> Arc<GenericParams>;
@@ -85,11 +82,8 @@ pub trait PersistentHirDatabase: SourceDatabase + AsRef<HirInterner> {
 
 #[salsa::query_group(HirDatabaseStorage)]
 pub trait HirDatabase: PersistentHirDatabase {
-    #[salsa::invoke(query_definitions::fn_scopes)]
-    fn fn_scopes(&self, func: Function) -> Arc<FnScopes>;
-
-    #[salsa::invoke(query_definitions::file_item)]
-    fn file_item(&self, source_item_id: SourceItemId) -> TreeArc<SyntaxNode>;
+    #[salsa::invoke(ExprScopes::expr_scopes_query)]
+    fn expr_scopes(&self, func: Function) -> Arc<ExprScopes>;
 
     #[salsa::invoke(crate::ty::infer)]
     fn infer(&self, func: Function) -> Arc<InferenceResult>;
@@ -105,4 +99,7 @@ pub trait HirDatabase: PersistentHirDatabase {
 
     #[salsa::invoke(crate::expr::body_syntax_mapping)]
     fn body_syntax_mapping(&self, func: Function) -> Arc<crate::expr::BodySyntaxMapping>;
+
+    #[salsa::invoke(crate::ty::method_resolution::CrateImplBlocks::impls_in_crate_query)]
+    fn impls_in_crate(&self, krate: Crate) -> Arc<CrateImplBlocks>;
 }
diff --git a/crates/ra_hir/src/expr.rs b/crates/ra_hir/src/expr.rs
index 37aa24677..f4a950418 100644
--- a/crates/ra_hir/src/expr.rs
+++ b/crates/ra_hir/src/expr.rs
@@ -10,8 +10,8 @@ use ra_syntax::{
 };
 
 use crate::{
-    Path, Name, HirDatabase, Function,
-    name::AsName,
+    Path, Name, Function,
+    name::AsName, HirDatabase,
     type_ref::{Mutability, TypeRef},
 };
 use crate::ty::primitive::{UintTy, UncertainIntTy, UncertainFloatTy};
diff --git a/crates/ra_hir/src/expr/scope.rs b/crates/ra_hir/src/expr/scope.rs
index f8b5ba581..b7971088d 100644
--- a/crates/ra_hir/src/expr/scope.rs
+++ b/crates/ra_hir/src/expr/scope.rs
@@ -12,7 +12,7 @@ use ra_arena::{Arena, RawId, impl_arena_id};
 use crate::{
     Name, AsName, Function,
     expr::{PatId, ExprId, Pat, Expr, Body, Statement, BodySyntaxMapping},
-    db::HirDatabase,
+    HirDatabase,
 };
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
diff --git a/crates/ra_hir/src/generics.rs b/crates/ra_hir/src/generics.rs
index 64c20a462..b0bd735bd 100644
--- a/crates/ra_hir/src/generics.rs
+++ b/crates/ra_hir/src/generics.rs
@@ -7,7 +7,7 @@ use std::sync::Arc;
 
 use ra_syntax::ast::{self, NameOwner, TypeParamsOwner};
 
-use crate::{db::HirDatabase, Name, AsName, Function, Struct, Enum, Trait, Type};
+use crate::{db::PersistentHirDatabase, Name, AsName, Function, Struct, Enum, Trait, Type};
 
 /// Data about a generic parameter (to a function, struct, impl, ...).
 #[derive(Clone, PartialEq, Eq, Debug)]
@@ -34,7 +34,7 @@ impl_froms!(GenericDef: Function, Struct, Enum, Trait, Type);
 
 impl GenericParams {
     pub(crate) fn generic_params_query(
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
         def: GenericDef,
     ) -> Arc<GenericParams> {
         let mut generics = GenericParams::default();
diff --git a/crates/ra_hir/src/ids.rs b/crates/ra_hir/src/ids.rs
index 0e4dc6261..95678bf70 100644
--- a/crates/ra_hir/src/ids.rs
+++ b/crates/ra_hir/src/ids.rs
@@ -10,6 +10,7 @@ use ra_arena::{Arena, RawId, ArenaId, impl_arena_id};
 use crate::{
     HirDatabase,
     Module,
+    PersistentHirDatabase,
 };
 
 #[derive(Debug, Default)]
@@ -62,7 +63,7 @@ pub struct HirFileId(HirFileIdRepr);
 impl HirFileId {
     /// For macro-expansion files, returns the file original source file the
     /// expansionoriginated from.
-    pub fn original_file(self, db: &impl HirDatabase) -> FileId {
+    pub fn original_file(self, db: &impl PersistentHirDatabase) -> FileId {
         match self.0 {
             HirFileIdRepr::File(file_id) => file_id,
             HirFileIdRepr::Macro(macro_call_id) => {
@@ -86,7 +87,10 @@ impl HirFileId {
         }
     }
 
-    pub(crate) fn hir_parse(db: &impl HirDatabase, file_id: HirFileId) -> TreeArc<SourceFile> {
+    pub(crate) fn hir_parse(
+        db: &impl PersistentHirDatabase,
+        file_id: HirFileId,
+    ) -> TreeArc<SourceFile> {
         match file_id.0 {
             HirFileIdRepr::File(file_id) => db.parse(file_id),
             HirFileIdRepr::Macro(m) => {
@@ -180,7 +184,7 @@ pub(crate) struct LocationCtx<DB> {
     file_id: HirFileId,
 }
 
-impl<'a, DB: HirDatabase> LocationCtx<&'a DB> {
+impl<'a, DB: PersistentHirDatabase> LocationCtx<&'a DB> {
     pub(crate) fn new(db: &'a DB, module: Module, file_id: HirFileId) -> LocationCtx<&'a DB> {
         LocationCtx {
             db,
@@ -199,7 +203,7 @@ impl<'a, DB: HirDatabase> LocationCtx<&'a DB> {
 
 pub(crate) trait AstItemDef<N: AstNode>: ArenaId + Clone {
     fn interner(interner: &HirInterner) -> &LocationIntener<ItemLoc<N>, Self>;
-    fn from_ast(ctx: LocationCtx<&impl HirDatabase>, ast: &N) -> Self {
+    fn from_ast(ctx: LocationCtx<&impl PersistentHirDatabase>, ast: &N) -> Self {
         let items = ctx.db.file_items(ctx.file_id);
         let raw = SourceItemId {
             file_id: ctx.file_id,
@@ -213,7 +217,7 @@ pub(crate) trait AstItemDef<N: AstNode>: ArenaId + Clone {
 
         Self::interner(ctx.db.as_ref()).loc2id(&loc)
     }
-    fn source(self, db: &impl HirDatabase) -> (HirFileId, TreeArc<N>) {
+    fn source(self, db: &impl PersistentHirDatabase) -> (HirFileId, TreeArc<N>) {
         let int = Self::interner(db.as_ref());
         let loc = int.id2loc(self);
         let syntax = db.file_item(loc.raw);
diff --git a/crates/ra_hir/src/impl_block.rs b/crates/ra_hir/src/impl_block.rs
index 5fc26324a..36d72b103 100644
--- a/crates/ra_hir/src/impl_block.rs
+++ b/crates/ra_hir/src/impl_block.rs
@@ -9,7 +9,7 @@ ast::{self, AstNode}};
 use crate::{
     Const, Type,
     Function, HirFileId,
-    db::HirDatabase,
+    PersistentHirDatabase,
     type_ref::TypeRef,
     ids::LocationCtx,
 };
@@ -91,7 +91,7 @@ pub struct ImplData {
 
 impl ImplData {
     pub(crate) fn from_ast(
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
         file_id: HirFileId,
         module: Module,
         node: &ast::ImplBlock,
@@ -174,7 +174,12 @@ impl ModuleImplBlocks {
         }
     }
 
-    fn collect(&mut self, db: &impl HirDatabase, module: Module, source_map: &mut ImplSourceMap) {
+    fn collect(
+        &mut self,
+        db: &impl PersistentHirDatabase,
+        module: Module,
+        source_map: &mut ImplSourceMap,
+    ) {
         let (file_id, module_source) = module.definition_source(db);
         let file_id: HirFileId = file_id.into();
         let node = match &module_source {
@@ -198,7 +203,7 @@ impl ModuleImplBlocks {
 }
 
 pub(crate) fn impls_in_module_with_source_map_query(
-    db: &impl HirDatabase,
+    db: &impl PersistentHirDatabase,
     module: Module,
 ) -> (Arc<ModuleImplBlocks>, Arc<ImplSourceMap>) {
     let mut source_map = ImplSourceMap::default();
@@ -209,12 +214,15 @@ pub(crate) fn impls_in_module_with_source_map_query(
     (Arc::new(result), Arc::new(source_map))
 }
 
-pub(crate) fn impls_in_module(db: &impl HirDatabase, module: Module) -> Arc<ModuleImplBlocks> {
+pub(crate) fn impls_in_module(
+    db: &impl PersistentHirDatabase,
+    module: Module,
+) -> Arc<ModuleImplBlocks> {
     db.impls_in_module_with_source_map(module).0
 }
 
 pub(crate) fn impls_in_module_source_map_query(
-    db: &impl HirDatabase,
+    db: &impl PersistentHirDatabase,
     module: Module,
 ) -> Arc<ImplSourceMap> {
     db.impls_in_module_with_source_map(module).1
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index 0b9ee63bf..905c53c7d 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -44,7 +44,7 @@ mod code_model_impl;
 mod marks;
 
 use crate::{
-    db::HirDatabase,
+    db::{HirDatabase, PersistentHirDatabase},
     name::{AsName, KnownName},
     ids::{SourceItemId, SourceFileItems},
 };
diff --git a/crates/ra_hir/src/macros.rs b/crates/ra_hir/src/macros.rs
index cf7220875..cb8a9312e 100644
--- a/crates/ra_hir/src/macros.rs
+++ b/crates/ra_hir/src/macros.rs
@@ -14,7 +14,7 @@ use ra_syntax::{
     ast::{self, NameOwner},
 };
 
-use crate::{HirDatabase, MacroCallId};
+use crate::{MacroCallId, PersistentHirDatabase};
 
 // Hard-coded defs for now :-(
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
@@ -157,7 +157,7 @@ impl MacroExpansion {
 }
 
 pub(crate) fn expand_macro_invocation(
-    db: &impl HirDatabase,
+    db: &impl PersistentHirDatabase,
     invoc: MacroCallId,
 ) -> Option<Arc<MacroExpansion>> {
     let loc = invoc.loc(db);
diff --git a/crates/ra_hir/src/mock.rs b/crates/ra_hir/src/mock.rs
index 7da15eca0..17bdd48c6 100644
--- a/crates/ra_hir/src/mock.rs
+++ b/crates/ra_hir/src/mock.rs
@@ -11,7 +11,11 @@ use crate::{db, HirInterner};
 
 pub const WORKSPACE: SourceRootId = SourceRootId(0);
 
-#[salsa::database(ra_db::SourceDatabaseStorage, db::HirDatabaseStorage)]
+#[salsa::database(
+    ra_db::SourceDatabaseStorage,
+    db::HirDatabaseStorage,
+    db::PersistentHirDatabaseStorage
+)]
 #[derive(Debug)]
 pub(crate) struct MockDatabase {
     events: Mutex<Option<Vec<salsa::Event<MockDatabase>>>>,
diff --git a/crates/ra_hir/src/module_tree.rs b/crates/ra_hir/src/module_tree.rs
index 1f327eeb2..a1aa3d8ce 100644
--- a/crates/ra_hir/src/module_tree.rs
+++ b/crates/ra_hir/src/module_tree.rs
@@ -13,13 +13,14 @@ use test_utils::tested_by;
 
 use crate::{
     Name, AsName, HirDatabase, SourceItemId, HirFileId, Problem, SourceFileItems, ModuleSource,
+    PersistentHirDatabase,
     Crate,
     ids::SourceFileItemId,
 };
 
 impl ModuleSource {
     pub(crate) fn new(
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
         file_id: HirFileId,
         decl_id: Option<SourceFileItemId>,
     ) -> ModuleSource {
@@ -47,7 +48,7 @@ pub struct Submodule {
 
 impl Submodule {
     pub(crate) fn submodules_query(
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
         file_id: HirFileId,
         decl_id: Option<SourceFileItemId>,
     ) -> Arc<Vec<Submodule>> {
@@ -133,7 +134,10 @@ struct LinkData {
 }
 
 impl ModuleTree {
-    pub(crate) fn module_tree_query(db: &impl HirDatabase, krate: Crate) -> Arc<ModuleTree> {
+    pub(crate) fn module_tree_query(
+        db: &impl PersistentHirDatabase,
+        krate: Crate,
+    ) -> Arc<ModuleTree> {
         db.check_canceled();
         let mut res = ModuleTree::default();
         res.init_crate(db, krate);
@@ -156,7 +160,7 @@ impl ModuleTree {
         Some(res)
     }
 
-    fn init_crate(&mut self, db: &impl HirDatabase, krate: Crate) {
+    fn init_crate(&mut self, db: &impl PersistentHirDatabase, krate: Crate) {
         let crate_graph = db.crate_graph();
         let file_id = crate_graph.crate_root(krate.crate_id);
         let source_root_id = db.file_source_root(file_id);
@@ -167,7 +171,7 @@ impl ModuleTree {
 
     fn init_subtree(
         &mut self,
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
         source_root: &SourceRoot,
         parent: Option<LinkId>,
         file_id: HirFileId,
@@ -287,14 +291,18 @@ impl LinkId {
     pub(crate) fn name(self, tree: &ModuleTree) -> &Name {
         &tree.links[self].name
     }
-    pub(crate) fn source(self, tree: &ModuleTree, db: &impl HirDatabase) -> TreeArc<ast::Module> {
+    pub(crate) fn source(
+        self,
+        tree: &ModuleTree,
+        db: &impl PersistentHirDatabase,
+    ) -> TreeArc<ast::Module> {
         let syntax_node = db.file_item(tree.links[self].source);
         ast::Module::cast(&syntax_node).unwrap().to_owned()
     }
 }
 
 fn resolve_submodule(
-    db: &impl HirDatabase,
+    db: &impl PersistentHirDatabase,
     file_id: HirFileId,
     name: &Name,
     is_root: bool,
diff --git a/crates/ra_hir/src/nameres.rs b/crates/ra_hir/src/nameres.rs
index 4573a72ba..f8627acbe 100644
--- a/crates/ra_hir/src/nameres.rs
+++ b/crates/ra_hir/src/nameres.rs
@@ -24,9 +24,8 @@ use rustc_hash::{FxHashMap, FxHashSet};
 
 use crate::{
     Module, ModuleDef,
-    Path, PathKind,
-    HirDatabase, Crate,
-    Name,
+    Path, PathKind, Crate,
+    Name, PersistentHirDatabase,
     module_tree::{ModuleId, ModuleTree},
     nameres::lower::{ImportId, LoweredModule, ImportData},
 };
@@ -166,7 +165,7 @@ struct Resolver<'a, DB> {
 
 impl<'a, DB> Resolver<'a, DB>
 where
-    DB: HirDatabase,
+    DB: PersistentHirDatabase,
 {
     fn new(
         db: &'a DB,
@@ -330,7 +329,7 @@ enum ReachedFixedPoint {
 }
 
 impl ItemMap {
-    pub(crate) fn item_map_query(db: &impl HirDatabase, krate: Crate) -> Arc<ItemMap> {
+    pub(crate) fn item_map_query(db: &impl PersistentHirDatabase, krate: Crate) -> Arc<ItemMap> {
         let start = time::Instant::now();
         let module_tree = db.module_tree(krate);
         let input = module_tree
@@ -352,7 +351,7 @@ impl ItemMap {
 
     pub(crate) fn resolve_path(
         &self,
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
         original_module: Module,
         path: &Path,
     ) -> PerNs<ModuleDef> {
@@ -363,7 +362,7 @@ impl ItemMap {
     // the result.
     fn resolve_path_fp(
         &self,
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
         original_module: Module,
         path: &Path,
     ) -> (PerNs<ModuleDef>, ReachedFixedPoint) {
diff --git a/crates/ra_hir/src/nameres/lower.rs b/crates/ra_hir/src/nameres/lower.rs
index 8df11a5f4..9a45fa61c 100644
--- a/crates/ra_hir/src/nameres/lower.rs
+++ b/crates/ra_hir/src/nameres/lower.rs
@@ -8,10 +8,10 @@ use ra_arena::{Arena, RawId, impl_arena_id, map::ArenaMap};
 use rustc_hash::FxHashMap;
 
 use crate::{
-    SourceItemId, Path, ModuleSource, HirDatabase, Name,
+    SourceItemId, Path, ModuleSource, Name,
     HirFileId, MacroCallLoc, AsName, PerNs, Function,
     ModuleDef, Module, Struct, Enum, Const, Static, Trait, Type,
-    ids::LocationCtx,
+    ids::LocationCtx, PersistentHirDatabase,
 };
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
@@ -58,21 +58,21 @@ impl ImportSourceMap {
 
 impl LoweredModule {
     pub(crate) fn lower_module_module_query(
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
         module: Module,
     ) -> Arc<LoweredModule> {
         db.lower_module(module).0
     }
 
     pub(crate) fn lower_module_source_map_query(
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
         module: Module,
     ) -> Arc<ImportSourceMap> {
         db.lower_module(module).1
     }
 
     pub(crate) fn lower_module_query(
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
         module: Module,
     ) -> (Arc<LoweredModule>, Arc<ImportSourceMap>) {
         let (file_id, source) = module.definition_source(db);
@@ -105,7 +105,7 @@ impl LoweredModule {
     fn fill(
         &mut self,
         source_map: &mut ImportSourceMap,
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
         module: Module,
         file_id: HirFileId,
         items: &mut Iterator<Item = ast::ItemOrMacro>,
@@ -137,7 +137,7 @@ impl LoweredModule {
     fn add_def_id(
         &mut self,
         source_map: &mut ImportSourceMap,
-        db: &impl HirDatabase,
+        db: &impl PersistentHirDatabase,
         module: Module,
         file_id: HirFileId,
         item: &ast::ModuleItem,
diff --git a/crates/ra_hir/src/nameres/tests.rs b/crates/ra_hir/src/nameres/tests.rs
index 9c5ca097e..1ce7bd146 100644
--- a/crates/ra_hir/src/nameres/tests.rs
+++ b/crates/ra_hir/src/nameres/tests.rs
@@ -6,7 +6,7 @@ use test_utils::{assert_eq_text, covers};
 
 use crate::{
     ItemMap, Resolution,
-    db::HirDatabase,
+    PersistentHirDatabase,
     mock::MockDatabase,
     module_tree::ModuleId,
 };
diff --git a/crates/ra_hir/src/query_definitions.rs b/crates/ra_hir/src/query_definitions.rs
index 734a98282..b4d8da1e6 100644
--- a/crates/ra_hir/src/query_definitions.rs
+++ b/crates/ra_hir/src/query_definitions.rs
@@ -6,17 +6,20 @@ use ra_syntax::{
 
 use crate::{
     SourceFileItems, SourceItemId, HirFileId,
-    db::HirDatabase,
+    PersistentHirDatabase,
 };
 
-pub(super) fn file_items(db: &impl HirDatabase, file_id: HirFileId) -> Arc<SourceFileItems> {
+pub(super) fn file_items(
+    db: &impl PersistentHirDatabase,
+    file_id: HirFileId,
+) -> Arc<SourceFileItems> {
     let source_file = db.hir_parse(file_id);
     let res = SourceFileItems::new(file_id, &source_file);
     Arc::new(res)
 }
 
 pub(super) fn file_item(
-    db: &impl HirDatabase,
+    db: &impl PersistentHirDatabase,
     source_item_id: SourceItemId,
 ) -> TreeArc<SyntaxNode> {
     let source_file = db.hir_parse(source_item_id.file_id);
diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index 60c231e82..d3e31981a 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -35,7 +35,7 @@ use test_utils::tested_by;
 use crate::{
     Module, Function, Struct, StructField, Enum, EnumVariant, Path, Name, ImplBlock,
     FnSignature, ExprScopes, ModuleDef, AdtDef,
-    db::HirDatabase,
+    HirDatabase,
     type_ref::{TypeRef, Mutability},
     name::KnownName,
     expr::{Body, Expr, BindingAnnotation, Literal, ExprId, Pat, PatId, UnaryOp, BinaryOp, Statement, FieldPat},
diff --git a/crates/ra_ide_api/src/db.rs b/crates/ra_ide_api/src/db.rs
index 6850811d7..3a9089c22 100644
--- a/crates/ra_ide_api/src/db.rs
+++ b/crates/ra_ide_api/src/db.rs
@@ -14,7 +14,8 @@ use crate::{LineIndex, symbol_index::{self, SymbolsDatabase}};
     ra_db::SourceDatabaseStorage,
     LineIndexDatabaseStorage,
     symbol_index::SymbolsDatabaseStorage,
-    hir::db::HirDatabaseStorage
+    hir::db::HirDatabaseStorage,
+    hir::db::PersistentHirDatabaseStorage
 )]
 #[derive(Debug)]
 pub(crate) struct RootDatabase {