6 files changed, 302 insertions, 375 deletions

diff --git a/crates/libanalysis/Cargo.toml b/crates/libanalysis/Cargo.toml
index 4c92951b1..88f29d7c8 100644
--- a/crates/libanalysis/Cargo.toml
+++ b/crates/libanalysis/Cargo.toml
@@ -14,6 +14,7 @@ fst = "0.3.1"
 im = "12.0.0"
 libsyntax2 = { path = "../libsyntax2" }
 libeditor = { path = "../libeditor" }
+salsa = { path = "../salsa" }
 
 [dev-dependencies]
 test_utils = { path = "../test_utils" }
diff --git a/crates/libanalysis/src/db.rs b/crates/libanalysis/src/db.rs
deleted file mode 100644
index d30e75fe2..000000000
--- a/crates/libanalysis/src/db.rs
+++ /dev/null
@@ -1,306 +0,0 @@
-use std::{
-    hash::{Hash, Hasher},
-    sync::Arc,
-    cell::RefCell,
-    fmt::Debug,
-    any::Any,
-};
-use parking_lot::Mutex;
-use libsyntax2::{File};
-use im;
-use {
-    FileId,
-    imp::{FileResolverImp},
-};
-
-#[derive(Debug)]
-pub(crate) struct DbHost {
-    db: Arc<Db>,
-}
-
-impl DbHost {
-    pub(crate) fn new() -> DbHost {
-        let db = Db {
-            file_resolver: FileResolverImp::default(),
-            files: im::HashMap::new(),
-            cache: Mutex::new(Cache::new())
-        };
-        DbHost { db: Arc::new(db) }
-    }
-    pub(crate) fn change_file(&mut self, file_id: FileId, text: Option<String>) {
-        let db = self.db_mut();
-        match text {
-            None => {
-                db.files.remove(&file_id);
-            }
-            Some(text) => {
-                db.files.insert(file_id, Arc::new(text));
-            }
-        }
-    }
-    pub(crate) fn set_file_resolver(&mut self, file_resolver: FileResolverImp) {
-        let db = self.db_mut();
-        db.file_resolver = file_resolver
-    }
-    pub(crate) fn query_ctx(&self) -> QueryCtx {
-        QueryCtx {
-            db: Arc::clone(&self.db),
-            stack: RefCell::new(Vec::new()),
-            trace: RefCell::new(Vec::new()),
-        }
-    }
-    fn db_mut(&mut self) -> &mut Db {
-        // NB: this "forks" the database
-        let db = Arc::make_mut(&mut self.db);
-        db.cache.get_mut().gen += 1;
-        db
-    }
-}
-
-type QueryInvocationId = (u32, u64);
-type Gen = u64;
-type OutputHash = u64;
-
-fn id<Q: Query>(params: &Q::Params) -> QueryInvocationId {
-    use std::collections::hash_map::DefaultHasher;
-    let mut hasher = DefaultHasher::new();
-    params.hash(&mut hasher);
-    (Q::ID, hasher.finish())
-}
-fn output_hash<Q: Query>(output: &Q::Output) -> OutputHash {
-    use std::collections::hash_map::DefaultHasher;
-    let mut hasher = DefaultHasher::new();
-    output.hash(&mut hasher);
-    hasher.finish()
-}
-
-#[derive(Debug)]
-pub(crate) struct Db {
-    file_resolver: FileResolverImp,
-    files: im::HashMap<FileId, Arc<String>>,
-    cache: Mutex<Cache>,
-}
-
-impl Clone for Db {
-    fn clone(&self) -> Db {
-        Db {
-            file_resolver: self.file_resolver.clone(),
-            files: self.files.clone(),
-            cache: Mutex::new(Cache::new()),
-        }
-    }
-}
-
-type QueryDeps = Vec<(QueryInvocationId, Arc<Any>, OutputHash)>;
-
-#[derive(Default, Debug)]
-pub(crate) struct Cache {
-    gen: Gen,
-    green: im::HashMap<QueryInvocationId, (Gen, OutputHash)>,
-    deps: im::HashMap<QueryInvocationId, QueryDeps>,
-    results: im::HashMap<QueryInvocationId, Arc<Any>>,
-}
-
-
-#[allow(type_alias_bounds)]
-pub(crate) type QueryCache<Q: Query> = im::HashMap<
-    <Q as Query>::Params,
-    <Q as Query>::Output
->;
-
-impl Cache {
-    fn new() -> Cache {
-        Default::default()
-    }
-
-    fn get_result<Q: Query>(&self, id: QueryInvocationId) -> Q::Output
-    where
-        Q::Output: Clone
-    {
-        let res = &self.results[&id];
-        let res = res.downcast_ref::<Q::Output>().unwrap();
-        res.clone()
-    }
-}
-
-pub(crate) struct QueryCtx {
-    db: Arc<Db>,
-    stack: RefCell<Vec<(QueryInvocationId, QueryDeps)>>,
-    pub(crate) trace: RefCell<Vec<TraceEvent>>,
-}
-
-#[derive(Clone, Copy, Debug)]
-pub(crate) struct TraceEvent {
-    pub(crate) query_id: u32,
-    pub(crate) kind: TraceEventKind
-}
-
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub(crate) enum TraceEventKind {
-    Start, Evaluating, Finish
-}
-
-impl QueryCtx {
-    pub(crate) fn get<Q: Get>(&self, params: &Q::Params) -> Q::Output {
-        let me = id::<Q>(params);
-        self.trace(TraceEvent { query_id: Q::ID, kind: TraceEventKind::Start });
-        let res = Q::get(self, params);
-        self.trace(TraceEvent { query_id: Q::ID, kind: TraceEventKind::Finish });
-        {
-            let mut stack = self.stack.borrow_mut();
-            if let Some((_, ref mut deps)) = stack.last_mut() {
-                let params = Arc::new(params.clone());
-                deps.push((me, params, output_hash::<Q>(&res)));
-            }
-        }
-
-        res
-    }
-    fn trace(&self, event: TraceEvent) {
-        self.trace.borrow_mut().push(event)
-    }
-}
-
-pub(crate) trait Query {
-    const ID: u32;
-    type Params: Hash + Eq + Debug + Clone + Any + 'static;
-    type Output: Hash + Debug + Any + 'static;
-}
-
-pub(crate) trait Get: Query {
-    fn get(ctx: &QueryCtx, params: &Self::Params) -> Self::Output;
-}
-
-impl<Q: Eval> Get for Q
-where
-    Q::Params: Clone,
-    Q::Output: Clone,
-{
-    fn get(ctx: &QueryCtx, params: &Self::Params) -> Self::Output {
-        if let Some(res) = try_reuse::<Q>(ctx, params) {
-            return res;
-        }
-
-        let me = id::<Q>(params);
-        ctx.trace(TraceEvent { query_id: Q::ID, kind: TraceEventKind::Evaluating });
-        ctx.stack.borrow_mut().push((me, Vec::new()));
-        let res = Self::eval(ctx, params);
-        let (also_me, deps) = ctx.stack.borrow_mut().pop().unwrap();
-        assert_eq!(also_me, me);
-        let mut cache = ctx.db.cache.lock();
-        cache.deps.insert(me, deps);
-        let gen = cache.gen;
-        let output_hash = output_hash::<Q>(&res);
-        let id = id::<Q>(params);
-        cache.green.insert(id, (gen, output_hash));
-        cache.results.insert(me, Arc::new(res.clone()));
-        res
-    }
-}
-
-fn try_reuse<Q: Eval>(ctx: &QueryCtx, params: &Q::Params) -> Option<Q::Output>
-where
-    Q::Params: Clone,
-    Q::Output: Clone,
-{
-    let id = id::<Q>(params);
-    let mut cache = ctx.db.cache.lock();
-    let curr_gen = cache.gen;
-    let old_hash = match *cache.green.get(&id)? {
-        (gen, _) if gen == curr_gen => {
-            return Some(cache.get_result::<Q>(id));
-        }
-        (_, hash) => hash,
-    };
-    let deps_are_fresh = cache.deps[&id]
-        .iter()
-        .all(|&(dep_id, _, dep_hash)| {
-            match cache.green.get(&dep_id) {
-                //TODO: store the value of parameters, and re-execute the query
-                Some((gen, hash)) if gen == &curr_gen && hash == &dep_hash => true,
-                _ => false,
-            }
-        });
-    if !deps_are_fresh {
-        return None;
-    }
-    cache.green.insert(id, (curr_gen, old_hash));
-    Some(cache.get_result::<Q>(id))
-}
-
-pub(crate) trait Eval: Query
-where
-    Self::Params: Clone,
-    Self::Output: Clone,
-{
-    fn eval(ctx: &QueryCtx, params: &Self::Params) -> Self::Output;
-}
-
-#[derive(Debug)]
-pub(crate) struct DbFiles {
-    db: Arc<Db>,
-}
-
-impl Hash for DbFiles {
-    fn hash<H: Hasher>(&self, hasher: &mut H) {
-        self.db.cache.lock().gen.hash(hasher)
-    }
-}
-
-impl DbFiles {
-    pub(crate) fn iter<'a>(&'a self) -> impl Iterator<Item=FileId> + 'a {
-        self.db.files.keys().cloned()
-    }
-    pub(crate) fn file_resolver(&self) -> FileResolverImp {
-        self.db.file_resolver.clone()
-    }
-}
-
-pub(crate) enum Files {}
-impl Query for Files {
-    const ID: u32 = 1;
-    type Params = ();
-    type Output = DbFiles;
-}
-impl Get for Files {
-    fn get(ctx: &QueryCtx, params: &()) -> DbFiles {
-        let res = DbFiles { db: Arc::clone(&ctx.db) };
-        let id = id::<Self>(params);
-        let hash = output_hash::<Self>(&res);
-        let mut cache = ctx.db.cache.lock();
-        let gen = cache.gen;
-        cache.green.insert(id, (gen, hash));
-        res
-    }
-}
-
-enum FileText {}
-impl Query for FileText {
-    const ID: u32 = 10;
-    type Params = FileId;
-    type Output = Arc<String>;
-}
-impl Get for FileText {
-    fn get(ctx: &QueryCtx, file_id: &FileId) -> Arc<String> {
-        let res = ctx.db.files[file_id].clone();
-        let id = id::<Self>(file_id);
-        let hash = output_hash::<Self>(&res);
-        let mut cache = ctx.db.cache.lock();
-        let gen = cache.gen;
-        cache.green.insert(id, (gen, hash));
-        res
-    }
-}
-
-pub(crate) enum FileSyntax {}
-impl Query for FileSyntax {
-    const ID: u32 = 20;
-    type Params = FileId;
-    type Output = File;
-}
-impl Eval for FileSyntax {
-    fn eval(ctx: &QueryCtx, file_id: &FileId) -> File {
-        let text = ctx.get::<FileText>(file_id);
-        File::parse(&text)
-    }
-}
diff --git a/crates/libanalysis/src/db/mod.rs b/crates/libanalysis/src/db/mod.rs
new file mode 100644
index 000000000..f68aab61c
--- /dev/null
+++ b/crates/libanalysis/src/db/mod.rs
@@ -0,0 +1,196 @@
+mod queries;
+
+use std::{
+    hash::{Hash},
+    sync::Arc,
+    fmt::Debug,
+    any::Any,
+    iter,
+};
+use im;
+use salsa;
+use {
+    FileId,
+    imp::{FileResolverImp},
+};
+
+
+#[derive(Clone, Default)]
+pub(crate) struct State {
+    pub(crate) resolver: FileResolverImp,
+    pub(crate) file_map: im::HashMap<FileId, Arc<str>>,
+}
+
+type Data = Arc<Any + Send + Sync + 'static>;
+
+pub(crate) struct QueryCtx<'a> {
+    inner: &'a salsa::QueryCtx<State, Data>
+}
+
+pub(crate) struct Db {
+    inner: salsa::Db<State, Data>
+}
+
+struct GroundQuery<T, R> {
+    id: u16,
+    f: fn(&State, &T) -> R,
+    h: fn(&R) -> u64,
+}
+
+pub(crate) struct Query<T, R> {
+    pub(crate) id: u16,
+    pub(crate) f: fn(QueryCtx, &T) -> R,
+}
+
+impl Db {
+    pub(crate) fn new(state: State) -> Db {
+        Db { inner: salsa::Db::new(query_config(), state) }
+    }
+    pub(crate) fn state(&self) -> &State {
+        self.inner.ground_data()
+    }
+    pub(crate) fn with_state(
+        &self,
+        new_state: State,
+        updated_files: &[FileId],
+        file_set_changed: bool,
+    ) -> Db {
+        let mut inv = salsa::Invalidations::new();
+        if file_set_changed {
+            inv.invalidate(
+                salsa::QueryTypeId(queries::FILE_SET.id),
+                iter::once(salsa::InputFingerprint(hash(&()))),
+            );
+        } else {
+            inv.invalidate(
+                salsa::QueryTypeId(queries::FILE_SET.id),
+                iter::empty(),
+            );
+        }
+        inv.invalidate(
+            salsa::QueryTypeId(queries::FILE_TEXT.id),
+            updated_files.iter().map(hash).map(salsa::InputFingerprint),
+        );
+        Db { inner: self.inner.with_ground_data(new_state, inv) }
+    }
+    pub(crate) fn get<T, R>(&self, q: Query<T, R>, params: T) -> (Arc<R>, Vec<u16>)
+    where
+        T: Hash + Send + Sync + 'static,
+        R: Send + Sync + 'static,
+    {
+        let query_id = salsa::QueryId(
+            salsa::QueryTypeId(q.id),
+            salsa::InputFingerprint(hash(&params)),
+        );
+        let params = Arc::new(params);
+        let (res, events) = self.inner.get(query_id, params);
+        let res = res.downcast().unwrap();
+        let events = events.into_iter().map(|it| it.0).collect();
+        (res, events)
+    }
+
+}
+
+impl<'a> QueryCtx<'a> {
+    fn get_g<T, R>(&self, q: GroundQuery<T, R>, params: T) -> Arc<R>
+    where
+        T: Hash + Send + Sync + 'static,
+        R: Send + Sync + 'static,
+     {
+        let query_id = salsa::QueryId(
+            salsa::QueryTypeId(q.id),
+            salsa::InputFingerprint(hash(&params)),
+        );
+        let res = self.inner.get(query_id, Arc::new(params));
+        res.downcast().unwrap()
+    }
+    pub(crate) fn get<T, R>(&self, q: Query<T, R>, params: T) -> Arc<R>
+    where
+        T: Hash + Send + Sync + 'static,
+        R: Send + Sync + 'static,
+     {
+        let query_id = salsa::QueryId(
+            salsa::QueryTypeId(q.id),
+            salsa::InputFingerprint(hash(&params)),
+        );
+        let res = self.inner.get(query_id, Arc::new(params));
+        res.downcast().unwrap()
+    }
+}
+
+fn query_config() -> salsa::QueryConfig<State, Data> {
+    let mut res = salsa::QueryConfig::new();
+    let queries: Vec<SalsaGroundQuery> = vec![
+        queries::FILE_TEXT.into(),
+        queries::FILE_SET.into(),
+    ];
+    for q in queries {
+        res = res.with_ground_query(q.query_type, q.f)
+    }
+    let queries: Vec<SalsaQuery> = vec![
+        queries::FILE_SYNTAX.into(),
+        ::module_map_db::MODULE_DESCR.into(),
+        ::module_map_db::RESOLVE_SUBMODULE.into(),
+        ::module_map_db::PARENT_MODULE.into(),
+    ];
+    for q in queries {
+        res = res.with_query(q.query_type, q.f);
+    }
+    res
+}
+
+struct SalsaGroundQuery {
+    query_type: salsa::QueryTypeId,
+    f: Box<Fn(&State, &Data) -> (Data, salsa::OutputFingerprint) + Send + Sync + 'static>,
+}
+
+impl<T, R> From<GroundQuery<T, R>> for SalsaGroundQuery
+where
+    T: Send + Sync + 'static,
+    R: Send + Sync + 'static,
+{
+    fn from(q: GroundQuery<T, R>) -> SalsaGroundQuery
+    {
+        SalsaGroundQuery {
+            query_type: salsa::QueryTypeId(q.id),
+            f: Box::new(move |state, data| {
+                let data: &T = data.downcast_ref().unwrap();
+                let res = (q.f)(state, data);
+                let h = (q.h)(&res);
+                (Arc::new(res), salsa::OutputFingerprint(h))
+            })
+        }
+    }
+}
+
+struct SalsaQuery {
+    query_type: salsa::QueryTypeId,
+    f: Box<Fn(&salsa::QueryCtx<State, Data>, &Data) -> (Data, salsa::OutputFingerprint) + Send + Sync + 'static>,
+}
+
+impl<T, R> From<Query<T, R>> for SalsaQuery
+where
+    T: Hash + Send + Sync + 'static,
+    R: Hash + Send + Sync + 'static,
+{
+    fn from(q: Query<T, R>) -> SalsaQuery
+    {
+        SalsaQuery {
+            query_type: salsa::QueryTypeId(q.id),
+            f: Box::new(move |ctx, data| {
+                let ctx = QueryCtx { inner: ctx };
+                let data: &T = data.downcast_ref().unwrap();
+                let res = (q.f)(ctx, data);
+                let h = hash(&res);
+                (Arc::new(res), salsa::OutputFingerprint(h))
+            })
+        }
+    }
+}
+
+fn hash<T: ::std::hash::Hash>(x: &T) -> u64 {
+    use std::hash::Hasher;
+    let mut hasher = ::std::collections::hash_map::DefaultHasher::new();
+    ::std::hash::Hash::hash(x, &mut hasher);
+    hasher.finish()
+}
diff --git a/crates/libanalysis/src/db/queries.rs b/crates/libanalysis/src/db/queries.rs
new file mode 100644
index 000000000..2d4aac6e9
--- /dev/null
+++ b/crates/libanalysis/src/db/queries.rs
@@ -0,0 +1,43 @@
+use std::sync::Arc;
+use libsyntax2::{File};
+use {
+    FileId, FileResolverImp,
+    db::{Query, GroundQuery, QueryCtx, hash},
+};
+
+
+impl<'a> QueryCtx<'a> {
+    pub(crate) fn file_set(&self) -> Arc<(Vec<FileId>, FileResolverImp)> {
+        self.get_g(FILE_SET, ())
+    }
+    pub(crate) fn file_text(&self, file_id: FileId) -> Arc<str> {
+        Arc::clone(&*self.get_g(FILE_TEXT, file_id))
+    }
+    pub(crate) fn file_syntax(&self, file_id: FileId) -> File {
+        (&*self.get(FILE_SYNTAX, file_id)).clone()
+    }
+}
+
+pub(super) const FILE_TEXT: GroundQuery<FileId, Arc<str>> = GroundQuery {
+    id: 10,
+    f: |state, id| state.file_map[&id].clone(),
+    h: hash,
+};
+
+pub(super) const FILE_SET: GroundQuery<(), (Vec<FileId>, FileResolverImp)> = GroundQuery {
+    id: 11,
+    f: |state, &()| {
+        let files = state.file_map.keys().cloned().collect();
+        let resolver = state.resolver.clone();
+        (files, resolver)
+    },
+    h: |(files, _)| hash(files),
+};
+
+pub(super) const FILE_SYNTAX: Query<FileId, File> = Query {
+    id: 20,
+    f: |ctx, file_id: &FileId| {
+        let text = ctx.file_text(*file_id);
+        File::parse(&*text)
+    }
+};
diff --git a/crates/libanalysis/src/lib.rs b/crates/libanalysis/src/lib.rs
index 3e77006c5..bca5d4c1d 100644
--- a/crates/libanalysis/src/lib.rs
+++ b/crates/libanalysis/src/lib.rs
@@ -10,6 +10,7 @@ extern crate relative_path;
 #[macro_use]
 extern crate crossbeam_channel;
 extern crate im;
+extern crate salsa;
 
 mod symbol_index;
 mod module_map;
diff --git a/crates/libanalysis/src/module_map_db.rs b/crates/libanalysis/src/module_map_db.rs
index 4d4bd9104..ff69cc0d2 100644
--- a/crates/libanalysis/src/module_map_db.rs
+++ b/crates/libanalysis/src/module_map_db.rs
@@ -2,66 +2,55 @@ use std::sync::Arc;
 use {
     FileId,
     db::{
-        Query, Eval, QueryCtx, FileSyntax, Files,
-        Cache, QueryCache,
+        Query, QueryCtx
     },
     module_map::resolve_submodule,
 };
 
-pub(crate) enum ModuleDescr {}
-impl Query for ModuleDescr {
-    const ID: u32 = 30;
-    type Params = FileId;
-    type Output = Arc<descr::ModuleDescr>;
-}
-
-enum ResolveSubmodule {}
-impl Query for ResolveSubmodule {
-    const ID: u32 = 31;
-    type Params = (FileId, descr::Submodule);
-    type Output = Arc<Vec<FileId>>;
-}
-
-enum ParentModule {}
-impl Query for ParentModule {
-    const ID: u32 = 40;
-    type Params = FileId;
-    type Output = Arc<Vec<FileId>>;
+impl<'a> QueryCtx<'a> {
+    fn module_descr(&self, file_id: FileId) -> Arc<descr::ModuleDescr> {
+        self.get(MODULE_DESCR, file_id)
+    }
+    fn resolve_submodule(&self, file_id: FileId, submod: descr::Submodule) -> Arc<Vec<FileId>> {
+        self.get(RESOLVE_SUBMODULE, (file_id, submod))
+    }
 }
 
-impl Eval for ModuleDescr {
-    fn eval(ctx: &QueryCtx, file_id: &FileId) -> Arc<descr::ModuleDescr> {
-        let file = ctx.get::<FileSyntax>(file_id);
-        Arc::new(descr::ModuleDescr::new(file.ast()))
+pub(crate) const MODULE_DESCR: Query<FileId, descr::ModuleDescr> = Query {
+    id: 30,
+    f: |ctx, &file_id| {
+        let file = ctx.file_syntax(file_id);
+        descr::ModuleDescr::new(file.ast())
     }
-}
+};
 
-impl Eval for ResolveSubmodule {
-    fn eval(ctx: &QueryCtx, &(file_id, ref submodule): &(FileId, descr::Submodule)) -> Arc<Vec<FileId>> {
-        let files = ctx.get::<Files>(&());
-        let res = resolve_submodule(file_id, &submodule.name, &files.file_resolver()).0;
-        Arc::new(res)
+pub(crate) const RESOLVE_SUBMODULE: Query<(FileId, descr::Submodule), Vec<FileId>> = Query {
+    id: 31,
+    f: |ctx, params| {
+        let files = ctx.file_set();
+        resolve_submodule(params.0, &params.1.name, &files.1).0
     }
-}
+};
 
-impl Eval for ParentModule {
-    fn eval(ctx: &QueryCtx, file_id: &FileId) -> Arc<Vec<FileId>> {
-        let files = ctx.get::<Files>(&());
-        let res = files.iter()
-            .map(|parent_id| (parent_id, ctx.get::<ModuleDescr>(&parent_id)))
+pub(crate) const PARENT_MODULE: Query<FileId, Vec<FileId>> = Query {
+    id: 40,
+    f: |ctx, file_id| {
+        let files = ctx.file_set();
+        let res = files.0.iter()
+            .map(|&parent_id| (parent_id, ctx.module_descr(parent_id)))
             .filter(|(parent_id, descr)| {
                 descr.submodules.iter()
                     .any(|subm| {
-                        ctx.get::<ResolveSubmodule>(&(*parent_id, subm.clone()))
+                        ctx.resolve_submodule(*parent_id, subm.clone())
                             .iter()
                             .any(|it| it == file_id)
                     })
             })
             .map(|(id, _)| id)
             .collect();
-        Arc::new(res)
+        res
     }
-}
+};
 
 mod descr {
     use libsyntax2::{
@@ -102,7 +91,7 @@ mod tests {
     use im;
     use relative_path::{RelativePath, RelativePathBuf};
     use {
-        db::{Query, DbHost, TraceEventKind},
+        db::{Query, Db, State},
         imp::FileResolverImp,
         FileId, FileResolver,
     };
@@ -126,7 +115,7 @@ mod tests {
     struct Fixture {
         next_file_id: u32,
         fm: im::HashMap<FileId, RelativePathBuf>,
-        db: DbHost,
+        db: Db,
     }
 
     impl Fixture {
@@ -134,7 +123,7 @@ mod tests {
             Fixture {
                 next_file_id: 1,
                 fm: im::HashMap::new(),
-                db: DbHost::new(),
+                db: Db::new(State::default()),
             }
         }
         fn add_file(&mut self, path: &str, text: &str) -> FileId {
@@ -142,36 +131,39 @@ mod tests {
             let file_id = FileId(self.next_file_id);
             self.next_file_id += 1;
             self.fm.insert(file_id, RelativePathBuf::from(&path[1..]));
-            self.db.change_file(file_id, Some(text.to_string()));
-            self.db.set_file_resolver(FileResolverImp::new(
+            let mut new_state = self.db.state().clone();
+            new_state.file_map.insert(file_id, text.to_string().into_boxed_str().into());
+            new_state.resolver = FileResolverImp::new(
                 Arc::new(FileMap(self.fm.clone()))
-            ));
-
+            );
+            self.db = self.db.with_state(new_state, &[file_id], true);
             file_id
         }
         fn remove_file(&mut self, file_id: FileId) {
             self.fm.remove(&file_id);
-            self.db.change_file(file_id, None);
-            self.db.set_file_resolver(FileResolverImp::new(
+            let mut new_state = self.db.state().clone();
+            new_state.file_map.remove(&file_id);
+            new_state.resolver = FileResolverImp::new(
                 Arc::new(FileMap(self.fm.clone()))
-            ))
+            );
+            self.db = self.db.with_state(new_state, &[file_id], true);
         }
         fn change_file(&mut self, file_id: FileId, new_text: &str) {
-            self.db.change_file(file_id, Some(new_text.to_string()));
+            let mut new_state = self.db.state().clone();
+            new_state.file_map.insert(file_id, new_text.to_string().into_boxed_str().into());
+            self.db = self.db.with_state(new_state, &[file_id], false);
         }
         fn check_parent_modules(
             &self,
             file_id: FileId,
             expected: &[FileId],
-            queries: &[(u32, u64)]
+            queries: &[(u16, u64)]
         ) {
-            let ctx = self.db.query_ctx();
-            let actual = ctx.get::<ParentModule>(&file_id);
+            let (actual, events) = self.db.get(PARENT_MODULE, file_id);
             assert_eq!(actual.as_slice(), expected);
             let mut counts = HashMap::new();
-            ctx.trace.borrow().iter()
-               .filter(|event| event.kind == TraceEventKind::Evaluating)
-               .for_each(|event| *counts.entry(event.query_id).or_insert(0) += 1);
+            events.into_iter()
+               .for_each(|event| *counts.entry(event).or_insert(0) += 1);
             for &(query_id, expected_count) in queries.iter() {
                 let actual_count = *counts.get(&query_id).unwrap_or(&0);
                 assert_eq!(
@@ -189,25 +181,25 @@ mod tests {
     fn test_parent_module() {
         let mut f = Fixture::new();
         let foo = f.add_file("/foo.rs", "");
-        // f.check_parent_modules(foo, &[], &[(ModuleDescr::ID, 1)]);
+        f.check_parent_modules(foo, &[], &[(MODULE_DESCR.id, 1)]);
 
         let lib = f.add_file("/lib.rs", "mod foo;");
-        f.check_parent_modules(foo, &[lib], &[(ModuleDescr::ID, 2)]);
-        f.check_parent_modules(foo, &[lib], &[(ModuleDescr::ID, 0)]);
+        f.check_parent_modules(foo, &[lib], &[(MODULE_DESCR.id, 1)]);
+        f.check_parent_modules(foo, &[lib], &[(MODULE_DESCR.id, 0)]);
 
         f.change_file(lib, "");
-        f.check_parent_modules(foo, &[], &[(ModuleDescr::ID, 2)]);
+        f.check_parent_modules(foo, &[], &[(MODULE_DESCR.id, 1)]);
 
-        // f.change_file(lib, "mod foo;");
-        // f.check_parent_modules(foo, &[lib], &[(ModuleDescr::ID, 2)]);
+        f.change_file(lib, "mod foo;");
+        f.check_parent_modules(foo, &[lib], &[(MODULE_DESCR.id, 1)]);
 
-        // f.change_file(lib, "mod bar;");
-        // f.check_parent_modules(foo, &[], &[(ModuleDescr::ID, 2)]);
+        f.change_file(lib, "mod bar;");
+        f.check_parent_modules(foo, &[], &[(MODULE_DESCR.id, 1)]);
 
-        // f.change_file(lib, "mod foo;");
-        // f.check_parent_modules(foo, &[lib], &[(ModuleDescr::ID, 2)]);
+        f.change_file(lib, "mod foo;");
+        f.check_parent_modules(foo, &[lib], &[(MODULE_DESCR.id, 1)]);
 
-        // f.remove_file(lib);
-        // f.check_parent_modules(foo, &[], &[(ModuleDescr::ID, 1)]);
+        f.remove_file(lib);
+        f.check_parent_modules(foo, &[], &[(MODULE_DESCR.id, 0)]);
     }
 }