Merge #147

147: Cancelation r=matklad a=matklad

This series of commits switch cancellation strategy from `JobToken` (which are cancellation tokens, explicitly controlled by the called) to salsa built-in auto cancellation. "Auto" means that, as soon as we advance the revision, all pending queries are cancelled automatically, and this looks like a semantic we actually want. 

"client-side" cancellation is a rare event, and it's ok to just punt on it. Automatic cancellation after the user types something in happens all the time. 

Co-authored-by: Aleksey Kladov <[email protected]>

16 files changed, 212 insertions, 262 deletions

diff --git a/Cargo.lock b/Cargo.lock
index bb0feec2e..f51914883 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -609,7 +609,6 @@ dependencies = [
 name = "ra_analysis"
 version = "0.1.0"
 dependencies = [
- "crossbeam-channel 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "fst 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "im 12.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/crates/ra_analysis/Cargo.toml b/crates/ra_analysis/Cargo.toml
index dd4ec8375..d7ac69fe8 100644
--- a/crates/ra_analysis/Cargo.toml
+++ b/crates/ra_analysis/Cargo.toml
@@ -7,7 +7,6 @@ authors = ["Aleksey Kladov <[email protected]>"]
 [dependencies]
 relative-path = "0.3.7"
 log = "0.4.2"
-crossbeam-channel = "0.2.4"
 parking_lot = "0.6.3"
 once_cell = "0.1.5"
 rayon = "1.0.2"
diff --git a/crates/ra_analysis/src/db.rs b/crates/ra_analysis/src/db.rs
index cce959669..09d74b9e7 100644
--- a/crates/ra_analysis/src/db.rs
+++ b/crates/ra_analysis/src/db.rs
@@ -1,17 +1,20 @@
-use crate::{
-    module_map::{ModuleDescriptorQuery, ModuleTreeQuery, ModulesDatabase},
-    symbol_index::SymbolIndex,
-    FileId, FileResolverImp,
+use std::{
+    fmt,
+    hash::{Hash, Hasher},
+    sync::Arc,
 };
+
 use ra_editor::LineIndex;
 use ra_syntax::File;
 use rustc_hash::FxHashSet;
 use salsa;
 
-use std::{
-    fmt,
-    hash::{Hash, Hasher},
-    sync::Arc,
+use crate::{
+    db,
+    Cancelable, Canceled,
+    module_map::{ModuleDescriptorQuery, ModuleTreeQuery, ModulesDatabase},
+    symbol_index::SymbolIndex,
+    FileId, FileResolverImp,
 };
 
 #[derive(Default)]
@@ -31,6 +34,14 @@ impl salsa::Database for RootDatabase {
     }
 }
 
+pub(crate) fn check_canceled(db: &impl salsa::Database) -> Cancelable<()> {
+    if db.salsa_runtime().is_current_revision_canceled() {
+        Err(Canceled)
+    } else {
+        Ok(())
+    }
+}
+
 impl salsa::ParallelDatabase for RootDatabase {
     fn fork(&self) -> Self {
         RootDatabase {
@@ -98,7 +109,7 @@ salsa::query_group! {
         fn file_lines(file_id: FileId) -> Arc<LineIndex> {
             type FileLinesQuery;
         }
-        fn file_symbols(file_id: FileId) -> Arc<SymbolIndex> {
+        fn file_symbols(file_id: FileId) -> Cancelable<Arc<SymbolIndex>> {
             type FileSymbolsQuery;
         }
     }
@@ -112,7 +123,8 @@ fn file_lines(db: &impl SyntaxDatabase, file_id: FileId) -> Arc<LineIndex> {
     let text = db.file_text(file_id);
     Arc::new(LineIndex::new(&*text))
 }
-fn file_symbols(db: &impl SyntaxDatabase, file_id: FileId) -> Arc<SymbolIndex> {
+fn file_symbols(db: &impl SyntaxDatabase, file_id: FileId) -> Cancelable<Arc<SymbolIndex>> {
+    db::check_canceled(db)?;
     let syntax = db.file_syntax(file_id);
-    Arc::new(SymbolIndex::for_file(file_id, syntax))
+    Ok(Arc::new(SymbolIndex::for_file(file_id, syntax)))
 }
diff --git a/crates/ra_analysis/src/descriptors.rs b/crates/ra_analysis/src/descriptors.rs
index 6f26f9935..310bf1585 100644
--- a/crates/ra_analysis/src/descriptors.rs
+++ b/crates/ra_analysis/src/descriptors.rs
@@ -1,4 +1,5 @@
-use crate::{imp::FileResolverImp, FileId};
+use std::collections::BTreeMap;
+
 use ra_syntax::{
     ast::{self, AstNode, NameOwner},
     text_utils::is_subrange,
@@ -6,7 +7,7 @@ use ra_syntax::{
 };
 use relative_path::RelativePathBuf;
 
-use std::collections::BTreeMap;
+use crate::{imp::FileResolverImp, FileId};
 
 #[derive(Debug, PartialEq, Eq, Hash)]
 pub struct ModuleDescriptor {
diff --git a/crates/ra_analysis/src/imp.rs b/crates/ra_analysis/src/imp.rs
index a67b1717a..32e9bb6d7 100644
--- a/crates/ra_analysis/src/imp.rs
+++ b/crates/ra_analysis/src/imp.rs
@@ -19,8 +19,8 @@ use rustc_hash::FxHashSet;
 use crate::{
     descriptors::{FnDescriptor, ModuleTreeDescriptor, Problem},
     roots::{ReadonlySourceRoot, SourceRoot, WritableSourceRoot},
-    CrateGraph, CrateId, Diagnostic, FileId, FileResolver, FileSystemEdit, JobToken, Position,
-    Query, SourceChange, SourceFileEdit,
+    CrateGraph, CrateId, Diagnostic, FileId, FileResolver, FileSystemEdit, Position,
+    Query, SourceChange, SourceFileEdit, Cancelable,
 };
 
 #[derive(Clone, Debug)]
@@ -148,19 +148,21 @@ impl AnalysisImpl {
     pub fn file_line_index(&self, file_id: FileId) -> Arc<LineIndex> {
         self.root(file_id).lines(file_id)
     }
-    pub fn world_symbols(&self, query: Query, token: &JobToken) -> Vec<(FileId, FileSymbol)> {
+    pub fn world_symbols(&self, query: Query) -> Cancelable<Vec<(FileId, FileSymbol)>> {
         let mut buf = Vec::new();
         if query.libs {
-            self.data.libs.iter().for_each(|it| it.symbols(&mut buf));
+            for lib in self.data.libs.iter() {
+                lib.symbols(&mut buf)?;
+            }
         } else {
-            self.data.root.symbols(&mut buf);
+            self.data.root.symbols(&mut buf)?;
         }
-        query.search(&buf, token)
+        Ok(query.search(&buf))
     }
-    pub fn parent_module(&self, file_id: FileId) -> Vec<(FileId, FileSymbol)> {
+    pub fn parent_module(&self, file_id: FileId) -> Cancelable<Vec<(FileId, FileSymbol)>> {
         let root = self.root(file_id);
-        let module_tree = root.module_tree();
-        module_tree
+        let module_tree = root.module_tree()?;
+        let res = module_tree
             .parent_modules(file_id)
             .iter()
             .map(|link| {
@@ -174,10 +176,11 @@ impl AnalysisImpl {
                 };
                 (file_id, sym)
             })
-            .collect()
+            .collect();
+        Ok(res)
     }
-    pub fn crate_for(&self, file_id: FileId) -> Vec<CrateId> {
-        let module_tree = self.root(file_id).module_tree();
+    pub fn crate_for(&self, file_id: FileId) -> Cancelable<Vec<CrateId>> {
+        let module_tree = self.root(file_id).module_tree()?;
         let crate_graph = &self.data.crate_graph;
         let mut res = Vec::new();
         let mut work = VecDeque::new();
@@ -195,7 +198,7 @@ impl AnalysisImpl {
                 .filter(|&id| visited.insert(id));
             work.extend(parents);
         }
-        res
+        Ok(res)
     }
     pub fn crate_root(&self, crate_id: CrateId) -> FileId {
         self.data.crate_graph.crate_roots[&crate_id]
@@ -204,15 +207,14 @@ impl AnalysisImpl {
         &self,
         file_id: FileId,
         offset: TextUnit,
-        token: &JobToken,
-    ) -> Vec<(FileId, FileSymbol)> {
+    ) -> Cancelable<Vec<(FileId, FileSymbol)>> {
         let root = self.root(file_id);
-        let module_tree = root.module_tree();
+        let module_tree = root.module_tree()?;
         let file = root.syntax(file_id);
         let syntax = file.syntax();
         if let Some(name_ref) = find_node_at_offset::<ast::NameRef>(syntax, offset) {
             // First try to resolve the symbol locally
-            if let Some((name, range)) = resolve_local_name(&file, offset, name_ref) {
+            return if let Some((name, range)) = resolve_local_name(&file, offset, name_ref) {
                 let mut vec = vec![];
                 vec.push((
                     file_id,
@@ -222,12 +224,11 @@ impl AnalysisImpl {
                         kind: NAME,
                     },
                 ));
-
-                return vec;
+                Ok(vec)
             } else {
                 // If that fails try the index based approach.
-                return self.index_resolve(name_ref, token);
-            }
+                self.index_resolve(name_ref)
+            };
         }
         if let Some(name) = find_node_at_offset::<ast::Name>(syntax, offset) {
             if let Some(module) = name.syntax().parent().and_then(ast::Module::cast) {
@@ -250,14 +251,14 @@ impl AnalysisImpl {
                         })
                         .collect();
 
-                    return res;
+                    return Ok(res);
                 }
             }
         }
-        vec![]
+        Ok(vec![])
     }
 
-    pub fn find_all_refs(&self, file_id: FileId, offset: TextUnit, _token: &JobToken) -> Vec<(FileId, TextRange)> {
+    pub fn find_all_refs(&self, file_id: FileId, offset: TextUnit) -> Vec<(FileId, TextRange)> {
         let root = self.root(file_id);
         let file = root.syntax(file_id);
         let syntax = file.syntax();
@@ -289,9 +290,9 @@ impl AnalysisImpl {
         ret
     }
 
-    pub fn diagnostics(&self, file_id: FileId) -> Vec<Diagnostic> {
+    pub fn diagnostics(&self, file_id: FileId) -> Cancelable<Vec<Diagnostic>> {
         let root = self.root(file_id);
-        let module_tree = root.module_tree();
+        let module_tree = root.module_tree()?;
         let syntax = root.syntax(file_id);
 
         let mut res = ra_editor::diagnostics(&syntax)
@@ -346,7 +347,7 @@ impl AnalysisImpl {
             };
             res.push(diag)
         }
-        res
+        Ok(res)
     }
 
     pub fn assists(&self, file_id: FileId, range: TextRange) -> Vec<SourceChange> {
@@ -379,18 +380,23 @@ impl AnalysisImpl {
         &self,
         file_id: FileId,
         offset: TextUnit,
-        token: &JobToken,
-    ) -> Option<(FnDescriptor, Option<usize>)> {
+    ) -> Cancelable<Option<(FnDescriptor, Option<usize>)>> {
         let root = self.root(file_id);
         let file = root.syntax(file_id);
         let syntax = file.syntax();
 
         // Find the calling expression and it's NameRef
-        let calling_node = FnCallNode::with_node(syntax, offset)?;
-        let name_ref = calling_node.name_ref()?;
+        let calling_node = match FnCallNode::with_node(syntax, offset) {
+            Some(node) => node,
+            None => return Ok(None),
+        };
+        let name_ref = match calling_node.name_ref() {
+            Some(name) => name,
+            None => return Ok(None),
+        };
 
         // Resolve the function's NameRef (NOTE: this isn't entirely accurate).
-        let file_symbols = self.index_resolve(name_ref, token);
+        let file_symbols = self.index_resolve(name_ref)?;
         for (_, fs) in file_symbols {
             if fs.kind == FN_DEF {
                 if let Some(fn_def) = find_node_at_offset(syntax, fs.node_range.start()) {
@@ -432,21 +438,21 @@ impl AnalysisImpl {
                             }
                         }
 
-                        return Some((descriptor, current_parameter));
+                        return Ok(Some((descriptor, current_parameter)));
                     }
                 }
             }
         }
 
-        None
+        Ok(None)
     }
 
-    fn index_resolve(&self, name_ref: ast::NameRef, token: &JobToken) -> Vec<(FileId, FileSymbol)> {
+    fn index_resolve(&self, name_ref: ast::NameRef) -> Cancelable<Vec<(FileId, FileSymbol)>> {
         let name = name_ref.text();
         let mut query = Query::new(name.to_string());
         query.exact();
         query.limit(4);
-        self.world_symbols(query, token)
+        self.world_symbols(query)
     }
 
     fn resolve_module(
diff --git a/crates/ra_analysis/src/job.rs b/crates/ra_analysis/src/job.rs
deleted file mode 100644
index 2871f9839..000000000
--- a/crates/ra_analysis/src/job.rs
+++ /dev/null
@@ -1,53 +0,0 @@
-use crossbeam_channel::{bounded, Receiver, Sender};
-
-pub struct JobHandle {
-    job_alive: Receiver<Never>,
-    _job_canceled: Sender<Never>,
-}
-
-pub struct JobToken {
-    _job_alive: Sender<Never>,
-    job_canceled: Receiver<Never>,
-}
-
-impl JobHandle {
-    pub fn new() -> (JobHandle, JobToken) {
-        let (sender_alive, receiver_alive) = bounded(0);
-        let (sender_canceled, receiver_canceled) = bounded(0);
-        let token = JobToken {
-            _job_alive: sender_alive,
-            job_canceled: receiver_canceled,
-        };
-        let handle = JobHandle {
-            job_alive: receiver_alive,
-            _job_canceled: sender_canceled,
-        };
-        (handle, token)
-    }
-    pub fn has_completed(&self) -> bool {
-        is_closed(&self.job_alive)
-    }
-    pub fn cancel(self) {}
-}
-
-impl JobToken {
-    pub fn is_canceled(&self) -> bool {
-        is_closed(&self.job_canceled)
-    }
-}
-
-// We don't actually send messages through the channels,
-// and instead just check if the channel is closed,
-// so we use uninhabited enum as a message type
-enum Never {}
-
-/// Nonblocking
-fn is_closed(chan: &Receiver<Never>) -> bool {
-    select! {
-        recv(chan, msg) => match msg {
-            None => true,
-            Some(never) => match never {}
-        }
-        default => false,
-    }
-}
diff --git a/crates/ra_analysis/src/lib.rs b/crates/ra_analysis/src/lib.rs
index 46cc0722b..28e0a12b2 100644
--- a/crates/ra_analysis/src/lib.rs
+++ b/crates/ra_analysis/src/lib.rs
@@ -7,8 +7,6 @@ extern crate ra_editor;
 extern crate ra_syntax;
 extern crate rayon;
 extern crate relative_path;
-#[macro_use]
-extern crate crossbeam_channel;
 extern crate im;
 extern crate rustc_hash;
 extern crate salsa;
@@ -16,27 +14,40 @@ extern crate salsa;
 mod db;
 mod descriptors;
 mod imp;
-mod job;
 mod module_map;
 mod roots;
 mod symbol_index;
 
 use std::{fmt::Debug, sync::Arc};
 
-use crate::imp::{AnalysisHostImpl, AnalysisImpl, FileResolverImp};
 use ra_syntax::{AtomEdit, File, TextRange, TextUnit};
 use relative_path::{RelativePath, RelativePathBuf};
 use rustc_hash::FxHashMap;
 
+use crate::imp::{AnalysisHostImpl, AnalysisImpl, FileResolverImp};
+
 pub use crate::{
     descriptors::FnDescriptor,
-    job::{JobHandle, JobToken},
 };
 pub use ra_editor::{
     CompletionItem, FileSymbol, Fold, FoldKind, HighlightedRange, LineIndex, Runnable,
     RunnableKind, StructureNode,
 };
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct Canceled;
+
+pub type Cancelable<T> = Result<T, Canceled>;
+
+impl std::fmt::Display for Canceled {
+    fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        fmt.write_str("Canceled")
+    }
+}
+
+impl std::error::Error for Canceled {
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct FileId(pub u32);
 
@@ -205,60 +216,57 @@ impl Analysis {
         let file = self.imp.file_syntax(file_id);
         ra_editor::file_structure(&file)
     }
-    pub fn symbol_search(&self, query: Query, token: &JobToken) -> Vec<(FileId, FileSymbol)> {
-        self.imp.world_symbols(query, token)
+    pub fn folding_ranges(&self, file_id: FileId) -> Vec<Fold> {
+        let file = self.imp.file_syntax(file_id);
+        ra_editor::folding_ranges(&file)
+    }
+    pub fn symbol_search(&self, query: Query) -> Cancelable<Vec<(FileId, FileSymbol)>> {
+        self.imp.world_symbols(query)
     }
     pub fn approximately_resolve_symbol(
         &self,
         file_id: FileId,
-        offset: TextUnit,
-        token: &JobToken,
-    ) -> Vec<(FileId, FileSymbol)> {
+        offset: TextUnit
+    ) -> Cancelable<Vec<(FileId, FileSymbol)>> {
         self.imp
-            .approximately_resolve_symbol(file_id, offset, token)
+            .approximately_resolve_symbol(file_id, offset)
     }
-    pub fn find_all_refs(&self, file_id: FileId, offset: TextUnit, token: &JobToken) -> Vec<(FileId, TextRange)> {
-        self.imp.find_all_refs(file_id, offset, token)
+    pub fn find_all_refs(&self, file_id: FileId, offset: TextUnit, ) -> Cancelable<Vec<(FileId, TextRange)>> {
+        Ok(self.imp.find_all_refs(file_id, offset))
     }
-    pub fn parent_module(&self, file_id: FileId) -> Vec<(FileId, FileSymbol)> {
+    pub fn parent_module(&self, file_id: FileId) -> Cancelable<Vec<(FileId, FileSymbol)>> {
         self.imp.parent_module(file_id)
     }
-    pub fn crate_for(&self, file_id: FileId) -> Vec<CrateId> {
+    pub fn crate_for(&self, file_id: FileId) -> Cancelable<Vec<CrateId>> {
         self.imp.crate_for(file_id)
     }
-    pub fn crate_root(&self, crate_id: CrateId) -> FileId {
-        self.imp.crate_root(crate_id)
+    pub fn crate_root(&self, crate_id: CrateId) -> Cancelable<FileId> {
+        Ok(self.imp.crate_root(crate_id))
     }
-    pub fn runnables(&self, file_id: FileId) -> Vec<Runnable> {
+    pub fn runnables(&self, file_id: FileId) -> Cancelable<Vec<Runnable>> {
         let file = self.imp.file_syntax(file_id);
-        ra_editor::runnables(&file)
+        Ok(ra_editor::runnables(&file))
     }
-    pub fn highlight(&self, file_id: FileId) -> Vec<HighlightedRange> {
+    pub fn highlight(&self, file_id: FileId) -> Cancelable<Vec<HighlightedRange>> {
         let file = self.imp.file_syntax(file_id);
-        ra_editor::highlight(&file)
+        Ok(ra_editor::highlight(&file))
     }
-    pub fn completions(&self, file_id: FileId, offset: TextUnit) -> Option<Vec<CompletionItem>> {
+    pub fn completions(&self, file_id: FileId, offset: TextUnit) -> Cancelable<Option<Vec<CompletionItem>>> {
         let file = self.imp.file_syntax(file_id);
-        ra_editor::scope_completion(&file, offset)
+        Ok(ra_editor::scope_completion(&file, offset))
     }
-    pub fn assists(&self, file_id: FileId, range: TextRange) -> Vec<SourceChange> {
-        self.imp.assists(file_id, range)
+    pub fn assists(&self, file_id: FileId, range: TextRange) -> Cancelable<Vec<SourceChange>> {
+        Ok(self.imp.assists(file_id, range))
     }
-    pub fn diagnostics(&self, file_id: FileId) -> Vec<Diagnostic> {
+    pub fn diagnostics(&self, file_id: FileId) -> Cancelable<Vec<Diagnostic>> {
         self.imp.diagnostics(file_id)
     }
-    pub fn folding_ranges(&self, file_id: FileId) -> Vec<Fold> {
-        let file = self.imp.file_syntax(file_id);
-        ra_editor::folding_ranges(&file)
-    }
-
     pub fn resolve_callable(
         &self,
         file_id: FileId,
         offset: TextUnit,
-        token: &JobToken,
-    ) -> Option<(FnDescriptor, Option<usize>)> {
-        self.imp.resolve_callable(file_id, offset, token)
+    ) -> Cancelable<Option<(FnDescriptor, Option<usize>)>> {
+        self.imp.resolve_callable(file_id, offset)
     }
 }
 
diff --git a/crates/ra_analysis/src/module_map.rs b/crates/ra_analysis/src/module_map.rs
index b15432498..3c800265a 100644
--- a/crates/ra_analysis/src/module_map.rs
+++ b/crates/ra_analysis/src/module_map.rs
@@ -1,37 +1,41 @@
+use std::sync::Arc;
+
 use crate::{
+    db,
+    Cancelable,
     db::SyntaxDatabase,
     descriptors::{ModuleDescriptor, ModuleTreeDescriptor},
     FileId,
 };
 
-use std::sync::Arc;
-
 salsa::query_group! {
     pub(crate) trait ModulesDatabase: SyntaxDatabase {
-        fn module_tree() -> Arc<ModuleTreeDescriptor> {
+        fn module_tree() -> Cancelable<Arc<ModuleTreeDescriptor>> {
             type ModuleTreeQuery;
         }
-        fn module_descriptor(file_id: FileId) -> Arc<ModuleDescriptor> {
+        fn module_descriptor(file_id: FileId) -> Cancelable<Arc<ModuleDescriptor>> {
             type ModuleDescriptorQuery;
         }
     }
 }
 
-fn module_descriptor(db: &impl ModulesDatabase, file_id: FileId) -> Arc<ModuleDescriptor> {
+fn module_descriptor(db: &impl ModulesDatabase, file_id: FileId) -> Cancelable<Arc<ModuleDescriptor>> {
+    db::check_canceled(db)?;
     let file = db.file_syntax(file_id);
-    Arc::new(ModuleDescriptor::new(file.ast()))
+    Ok(Arc::new(ModuleDescriptor::new(file.ast())))
 }
 
-fn module_tree(db: &impl ModulesDatabase) -> Arc<ModuleTreeDescriptor> {
+fn module_tree(db: &impl ModulesDatabase) -> Cancelable<Arc<ModuleTreeDescriptor>> {
+    db::check_canceled(db)?;
     let file_set = db.file_set();
     let mut files = Vec::new();
     for &file_id in file_set.files.iter() {
-        let module_descr = db.module_descriptor(file_id);
+        let module_descr = db.module_descriptor(file_id)?;
         files.push((file_id, module_descr));
     }
     let res = ModuleTreeDescriptor::new(
         files.iter().map(|(file_id, descr)| (*file_id, &**descr)),
         &file_set.resolver,
     );
-    Arc::new(res)
+    Ok(Arc::new(res))
 }
diff --git a/crates/ra_analysis/src/roots.rs b/crates/ra_analysis/src/roots.rs
index 19c84df65..123c4acfa 100644
--- a/crates/ra_analysis/src/roots.rs
+++ b/crates/ra_analysis/src/roots.rs
@@ -8,6 +8,7 @@ use rustc_hash::{FxHashMap, FxHashSet};
 use salsa::Database;
 
 use crate::{
+    Cancelable,
     db::{self, FilesDatabase, SyntaxDatabase},
     descriptors::{ModuleDescriptor, ModuleTreeDescriptor},
     imp::FileResolverImp,
@@ -18,10 +19,10 @@ use crate::{
 
 pub(crate) trait SourceRoot {
     fn contains(&self, file_id: FileId) -> bool;
-    fn module_tree(&self) -> Arc<ModuleTreeDescriptor>;
+    fn module_tree(&self) -> Cancelable<Arc<ModuleTreeDescriptor>>;
     fn lines(&self, file_id: FileId) -> Arc<LineIndex>;
     fn syntax(&self, file_id: FileId) -> File;
-    fn symbols(&self, acc: &mut Vec<Arc<SymbolIndex>>);
+    fn symbols(&self, acc: &mut Vec<Arc<SymbolIndex>>) -> Cancelable<()>;
 }
 
 #[derive(Default, Debug, Clone)]
@@ -64,7 +65,7 @@ impl WritableSourceRoot {
 }
 
 impl SourceRoot for WritableSourceRoot {
-    fn module_tree(&self) -> Arc<ModuleTreeDescriptor> {
+    fn module_tree(&self) -> Cancelable<Arc<ModuleTreeDescriptor>> {
         self.db.module_tree()
     }
     fn contains(&self, file_id: FileId) -> bool {
@@ -76,14 +77,12 @@ impl SourceRoot for WritableSourceRoot {
     fn syntax(&self, file_id: FileId) -> File {
         self.db.file_syntax(file_id)
     }
-    fn symbols<'a>(&'a self, acc: &mut Vec<Arc<SymbolIndex>>) {
-        let db = &self.db;
-        let symbols = db.file_set();
-        let symbols = symbols
-            .files
-            .iter()
-            .map(|&file_id| db.file_symbols(file_id));
-        acc.extend(symbols);
+    fn symbols<'a>(&'a self, acc: &mut Vec<Arc<SymbolIndex>>) -> Cancelable<()> {
+        for &file_id in self.db.file_set().files.iter() {
+            let symbols = self.db.file_symbols(file_id)?;
+            acc.push(symbols)
+        }
+        Ok(())
     }
 }
 
@@ -167,8 +166,8 @@ impl ReadonlySourceRoot {
 }
 
 impl SourceRoot for ReadonlySourceRoot {
-    fn module_tree(&self) -> Arc<ModuleTreeDescriptor> {
-        Arc::clone(&self.module_tree)
+    fn module_tree(&self) -> Cancelable<Arc<ModuleTreeDescriptor>> {
+        Ok(Arc::clone(&self.module_tree))
     }
     fn contains(&self, file_id: FileId) -> bool {
         self.file_map.contains_key(&file_id)
@@ -179,7 +178,8 @@ impl SourceRoot for ReadonlySourceRoot {
     fn syntax(&self, file_id: FileId) -> File {
         self.data(file_id).syntax().clone()
     }
-    fn symbols(&self, acc: &mut Vec<Arc<SymbolIndex>>) {
-        acc.push(Arc::clone(&self.symbol_index))
+    fn symbols(&self, acc: &mut Vec<Arc<SymbolIndex>>) -> Cancelable<()> {
+        acc.push(Arc::clone(&self.symbol_index));
+        Ok(())
     }
 }
diff --git a/crates/ra_analysis/src/symbol_index.rs b/crates/ra_analysis/src/symbol_index.rs
index 51eef8170..a0f3c0437 100644
--- a/crates/ra_analysis/src/symbol_index.rs
+++ b/crates/ra_analysis/src/symbol_index.rs
@@ -1,4 +1,8 @@
-use crate::{FileId, JobToken, Query};
+use std::{
+    hash::{Hash, Hasher},
+    sync::Arc,
+};
+
 use fst::{self, Streamer};
 use ra_editor::{file_symbols, FileSymbol};
 use ra_syntax::{
@@ -7,10 +11,7 @@ use ra_syntax::{
 };
 use rayon::prelude::*;
 
-use std::{
-    hash::{Hash, Hasher},
-    sync::Arc,
-};
+use crate::{FileId, Query};
 
 #[derive(Debug)]
 pub(crate) struct SymbolIndex {
@@ -59,7 +60,6 @@ impl Query {
     pub(crate) fn search(
         self,
         indices: &[Arc<SymbolIndex>],
-        token: &JobToken,
     ) -> Vec<(FileId, FileSymbol)> {
         let mut op = fst::map::OpBuilder::new();
         for file_symbols in indices.iter() {
@@ -69,7 +69,7 @@ impl Query {
         let mut stream = op.union();
         let mut res = Vec::new();
         while let Some((_, indexed_values)) = stream.next() {
-            if res.len() >= self.limit || token.is_canceled() {
+            if res.len() >= self.limit {
                 break;
             }
             for indexed_value in indexed_values {
diff --git a/crates/ra_analysis/tests/tests.rs b/crates/ra_analysis/tests/tests.rs
index 0c2c69ea0..7ae3d0eeb 100644
--- a/crates/ra_analysis/tests/tests.rs
+++ b/crates/ra_analysis/tests/tests.rs
@@ -7,15 +7,15 @@ extern crate test_utils;
 
 use std::sync::Arc;
 
-use ra_analysis::{
-    Analysis, AnalysisHost, CrateGraph, CrateId, FileId, FileResolver, FnDescriptor, JobHandle,
-};
 use ra_syntax::TextRange;
-
 use relative_path::{RelativePath, RelativePathBuf};
 use rustc_hash::FxHashMap;
 use test_utils::{assert_eq_dbg, extract_offset};
 
+use ra_analysis::{
+    Analysis, AnalysisHost, CrateGraph, CrateId, FileId, FileResolver, FnDescriptor,
+};
+
 #[derive(Debug)]
 struct FileMap(Vec<(FileId, RelativePathBuf)>);
 
@@ -64,24 +64,22 @@ fn get_signature(text: &str) -> (FnDescriptor, Option<usize>) {
     let (offset, code) = extract_offset(text);
     let code = code.as_str();
 
-    let (_handle, token) = JobHandle::new();
     let snap = analysis(&[("/lib.rs", code)]);
 
-    snap.resolve_callable(FileId(1), offset, &token).unwrap()
+    snap.resolve_callable(FileId(1), offset).unwrap().unwrap()
 }
 
 #[test]
 fn test_resolve_module() {
     let snap = analysis(&[("/lib.rs", "mod foo;"), ("/foo.rs", "")]);
-    let (_handle, token) = JobHandle::new();
-    let symbols = snap.approximately_resolve_symbol(FileId(1), 4.into(), &token);
+    let symbols = snap.approximately_resolve_symbol(FileId(1), 4.into()).unwrap();
     assert_eq_dbg(
         r#"[(FileId(2), FileSymbol { name: "foo", node_range: [0; 0), kind: MODULE })]"#,
         &symbols,
     );
 
     let snap = analysis(&[("/lib.rs", "mod foo;"), ("/foo/mod.rs", "")]);
-    let symbols = snap.approximately_resolve_symbol(FileId(1), 4.into(), &token);
+    let symbols = snap.approximately_resolve_symbol(FileId(1), 4.into()).unwrap();
     assert_eq_dbg(
         r#"[(FileId(2), FileSymbol { name: "foo", node_range: [0; 0), kind: MODULE })]"#,
         &symbols,
@@ -91,7 +89,7 @@ fn test_resolve_module() {
 #[test]
 fn test_unresolved_module_diagnostic() {
     let snap = analysis(&[("/lib.rs", "mod foo;")]);
-    let diagnostics = snap.diagnostics(FileId(1));
+    let diagnostics = snap.diagnostics(FileId(1)).unwrap();
     assert_eq_dbg(
         r#"[Diagnostic {
             message: "unresolved module",
@@ -108,14 +106,14 @@ fn test_unresolved_module_diagnostic() {
 #[test]
 fn test_unresolved_module_diagnostic_no_diag_for_inline_mode() {
     let snap = analysis(&[("/lib.rs", "mod foo {}")]);
-    let diagnostics = snap.diagnostics(FileId(1));
+    let diagnostics = snap.diagnostics(FileId(1)).unwrap();
     assert_eq_dbg(r#"[]"#, &diagnostics);
 }
 
 #[test]
 fn test_resolve_parent_module() {
     let snap = analysis(&[("/lib.rs", "mod foo;"), ("/foo.rs", "")]);
-    let symbols = snap.parent_module(FileId(2));
+    let symbols = snap.parent_module(FileId(2)).unwrap();
     assert_eq_dbg(
         r#"[(FileId(1), FileSymbol { name: "foo", node_range: [0; 8), kind: MODULE })]"#,
         &symbols,
@@ -126,7 +124,7 @@ fn test_resolve_parent_module() {
 fn test_resolve_crate_root() {
     let mut host = analysis_host(&[("/lib.rs", "mod foo;"), ("/foo.rs", "")]);
     let snap = host.analysis();
-    assert!(snap.crate_for(FileId(2)).is_empty());
+    assert!(snap.crate_for(FileId(2)).unwrap().is_empty());
 
     let crate_graph = CrateGraph {
         crate_roots: {
@@ -138,7 +136,7 @@ fn test_resolve_crate_root() {
     host.set_crate_graph(crate_graph);
     let snap = host.analysis();
 
-    assert_eq!(snap.crate_for(FileId(2)), vec![CrateId(1)],);
+    assert_eq!(snap.crate_for(FileId(2)).unwrap(), vec![CrateId(1)],);
 }
 
 #[test]
@@ -232,10 +230,9 @@ fn get_all_refs(text: &str) -> Vec<(FileId, TextRange)> {
     let (offset, code) = extract_offset(text);
     let code = code.as_str();
 
-    let (_handle, token) = JobHandle::new();
     let snap = analysis(&[("/lib.rs", code)]);
 
-    snap.find_all_refs(FileId(1), offset, &token)
+    snap.find_all_refs(FileId(1), offset).unwrap()
 }
 
 #[test]
@@ -266,4 +263,4 @@ fn test_find_all_refs_for_param_inside() {
 
     let refs = get_all_refs(code);
     assert_eq!(refs.len(), 2);
-}
\ No newline at end of file
+}
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 639fe4553..f5dff4c80 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -1,12 +1,13 @@
-use rustc_hash::FxHashMap;
+use std::collections::HashMap;
 
+use rustc_hash::FxHashMap;
 use languageserver_types::{
     CodeActionResponse, Command, CompletionItem, CompletionItemKind, Diagnostic,
     DiagnosticSeverity, DocumentSymbol, FoldingRange, FoldingRangeKind, FoldingRangeParams,
     InsertTextFormat, Location, Position, SymbolInformation, TextDocumentIdentifier, TextEdit,
     RenameParams, WorkspaceEdit, PrepareRenameResponse
 };
-use ra_analysis::{FileId, FoldKind, JobToken, Query, RunnableKind};
+use ra_analysis::{FileId, FoldKind, Query, RunnableKind};
 use ra_syntax::text_utils::contains_offset_nonstrict;
 use serde_json::to_value;
 
@@ -18,12 +19,9 @@ use crate::{
     Result,
 };
 
-use std::collections::HashMap;
-
 pub fn handle_syntax_tree(
     world: ServerWorld,
     params: req::SyntaxTreeParams,
-    _token: JobToken,
 ) -> Result<String> {
     let id = params.text_document.try_conv_with(&world)?;
     let res = world.analysis().syntax_tree(id);
@@ -33,7 +31,6 @@ pub fn handle_syntax_tree(
 pub fn handle_extend_selection(
     world: ServerWorld,
     params: req::ExtendSelectionParams,
-    _token: JobToken,
 ) -> Result<req::ExtendSelectionResult> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let file = world.analysis().file_syntax(file_id);
@@ -51,7 +48,6 @@ pub fn handle_extend_selection(
 pub fn handle_find_matching_brace(
     world: ServerWorld,
     params: req::FindMatchingBraceParams,
-    _token: JobToken,
 ) -> Result<Vec<Position>> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let file = world.analysis().file_syntax(file_id);
@@ -74,7 +70,6 @@ pub fn handle_find_matching_brace(
 pub fn handle_join_lines(
     world: ServerWorld,
     params: req::JoinLinesParams,
-    _token: JobToken,
 ) -> Result<req::SourceChange> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let line_index = world.analysis().file_line_index(file_id);
@@ -88,7 +83,6 @@ pub fn handle_join_lines(
 pub fn handle_on_enter(
     world: ServerWorld,
     params: req::TextDocumentPositionParams,
-    _token: JobToken,
 ) -> Result<Option<req::SourceChange>> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let line_index = world.analysis().file_line_index(file_id);
@@ -102,7 +96,6 @@ pub fn handle_on_enter(
 pub fn handle_on_type_formatting(
     world: ServerWorld,
     params: req::DocumentOnTypeFormattingParams,
-    _token: JobToken,
 ) -> Result<Option<Vec<TextEdit>>> {
     if params.ch != "=" {
         return Ok(None);
@@ -122,7 +115,6 @@ pub fn handle_on_type_formatting(
 pub fn handle_document_symbol(
     world: ServerWorld,
     params: req::DocumentSymbolParams,
-    _token: JobToken,
 ) -> Result<Option<req::DocumentSymbolResponse>> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let line_index = world.analysis().file_line_index(file_id);
@@ -161,7 +153,6 @@ pub fn handle_document_symbol(
 pub fn handle_workspace_symbol(
     world: ServerWorld,
     params: req::WorkspaceSymbolParams,
-    token: JobToken,
 ) -> Result<Option<Vec<SymbolInformation>>> {
     let all_symbols = params.query.contains("#");
     let libs = params.query.contains("*");
@@ -181,11 +172,11 @@ pub fn handle_workspace_symbol(
         q.limit(128);
         q
     };
-    let mut res = exec_query(&world, query, &token)?;
+    let mut res = exec_query(&world, query)?;
     if res.is_empty() && !all_symbols {
         let mut query = Query::new(params.query);
         query.limit(128);
-        res = exec_query(&world, query, &token)?;
+        res = exec_query(&world, query)?;
     }
 
     return Ok(Some(res));
@@ -193,10 +184,9 @@ pub fn handle_workspace_symbol(
     fn exec_query(
         world: &ServerWorld,
         query: Query,
-        token: &JobToken,
     ) -> Result<Vec<SymbolInformation>> {
         let mut res = Vec::new();
-        for (file_id, symbol) in world.analysis().symbol_search(query, token) {
+        for (file_id, symbol) in world.analysis().symbol_search(query)? {
             let line_index = world.analysis().file_line_index(file_id);
             let info = SymbolInformation {
                 name: symbol.name.to_string(),
@@ -214,7 +204,6 @@ pub fn handle_workspace_symbol(
 pub fn handle_goto_definition(
     world: ServerWorld,
     params: req::TextDocumentPositionParams,
-    token: JobToken,
 ) -> Result<Option<req::GotoDefinitionResponse>> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let line_index = world.analysis().file_line_index(file_id);
@@ -222,7 +211,7 @@ pub fn handle_goto_definition(
     let mut res = Vec::new();
     for (file_id, symbol) in world
         .analysis()
-        .approximately_resolve_symbol(file_id, offset, &token)
+        .approximately_resolve_symbol(file_id, offset)?
     {
         let line_index = world.analysis().file_line_index(file_id);
         let location = to_location(file_id, symbol.node_range, &world, &line_index)?;
@@ -234,11 +223,10 @@ pub fn handle_goto_definition(
 pub fn handle_parent_module(
     world: ServerWorld,
     params: TextDocumentIdentifier,
-    _token: JobToken,
 ) -> Result<Vec<Location>> {
     let file_id = params.try_conv_with(&world)?;
     let mut res = Vec::new();
-    for (file_id, symbol) in world.analysis().parent_module(file_id) {
+    for (file_id, symbol) in world.analysis().parent_module(file_id)? {
         let line_index = world.analysis().file_line_index(file_id);
         let location = to_location(file_id, symbol.node_range, &world, &line_index)?;
         res.push(location);
@@ -249,20 +237,19 @@ pub fn handle_parent_module(
 pub fn handle_runnables(
     world: ServerWorld,
     params: req::RunnablesParams,
-    _token: JobToken,
 ) -> Result<Vec<req::Runnable>> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let line_index = world.analysis().file_line_index(file_id);
     let offset = params.position.map(|it| it.conv_with(&line_index));
     let mut res = Vec::new();
-    for runnable in world.analysis().runnables(file_id) {
+    for runnable in world.analysis().runnables(file_id)? {
         if let Some(offset) = offset {
             if !contains_offset_nonstrict(runnable.range, offset) {
                 continue;
             }
         }
 
-        let args = runnable_args(&world, file_id, &runnable.kind);
+        let args = runnable_args(&world, file_id, &runnable.kind)?;
 
         let r = req::Runnable {
             range: runnable.range.conv_with(&line_index),
@@ -282,9 +269,9 @@ pub fn handle_runnables(
     }
     return Ok(res);
 
-    fn runnable_args(world: &ServerWorld, file_id: FileId, kind: &RunnableKind) -> Vec<String> {
-        let spec = if let Some(&crate_id) = world.analysis().crate_for(file_id).first() {
-            let file_id = world.analysis().crate_root(crate_id);
+    fn runnable_args(world: &ServerWorld, file_id: FileId, kind: &RunnableKind) -> Result<Vec<String>> {
+        let spec = if let Some(&crate_id) = world.analysis().crate_for(file_id)?.first() {
+            let file_id = world.analysis().crate_root(crate_id)?;
             let path = world.path_map.get_path(file_id);
             world
                 .workspaces
@@ -319,7 +306,7 @@ pub fn handle_runnables(
                 }
             }
         }
-        res
+        Ok(res)
     }
 
     fn spec_args(pkg_name: &str, tgt_name: &str, tgt_kind: TargetKind, buf: &mut Vec<String>) {
@@ -353,21 +340,19 @@ pub fn handle_runnables(
 pub fn handle_decorations(
     world: ServerWorld,
     params: TextDocumentIdentifier,
-    _token: JobToken,
 ) -> Result<Vec<Decoration>> {
     let file_id = params.try_conv_with(&world)?;
-    Ok(highlight(&world, file_id))
+    highlight(&world, file_id)
 }
 
 pub fn handle_completion(
     world: ServerWorld,
     params: req::CompletionParams,
-    _token: JobToken,
 ) -> Result<Option<req::CompletionResponse>> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let line_index = world.analysis().file_line_index(file_id);
     let offset = params.position.conv_with(&line_index);
-    let items = match world.analysis().completions(file_id, offset) {
+    let items = match world.analysis().completions(file_id, offset)? {
         None => return Ok(None),
         Some(items) => items,
     };
@@ -394,7 +379,6 @@ pub fn handle_completion(
 pub fn handle_folding_range(
     world: ServerWorld,
     params: FoldingRangeParams,
-    _token: JobToken,
 ) -> Result<Option<Vec<FoldingRange>>> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let line_index = world.analysis().file_line_index(file_id);
@@ -427,7 +411,6 @@ pub fn handle_folding_range(
 pub fn handle_signature_help(
     world: ServerWorld,
     params: req::TextDocumentPositionParams,
-    token: JobToken,
 ) -> Result<Option<req::SignatureHelp>> {
     use languageserver_types::{ParameterInformation, SignatureInformation};
 
@@ -436,7 +419,7 @@ pub fn handle_signature_help(
     let offset = params.position.conv_with(&line_index);
 
     if let Some((descriptor, active_param)) =
-        world.analysis().resolve_callable(file_id, offset, &token)
+        world.analysis().resolve_callable(file_id, offset)?
     {
         let parameters: Vec<ParameterInformation> = descriptor
             .params
@@ -466,7 +449,6 @@ pub fn handle_signature_help(
 pub fn handle_prepare_rename(
     world: ServerWorld,
     params: req::TextDocumentPositionParams,
-    token: JobToken,
 ) -> Result<Option<PrepareRenameResponse>> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let line_index = world.analysis().file_line_index(file_id);
@@ -474,7 +456,7 @@ pub fn handle_prepare_rename(
 
     // We support renaming references like handle_rename does.
     // In the future we may want to reject the renaming of things like keywords here too.
-    let refs = world.analysis().find_all_refs(file_id, offset, &token);
+    let refs = world.analysis().find_all_refs(file_id, offset)?;
     if refs.is_empty() {
         return Ok(None);
     }
@@ -488,7 +470,6 @@ pub fn handle_prepare_rename(
 pub fn handle_rename(
     world: ServerWorld,
     params: RenameParams,
-    token: JobToken,
 ) -> Result<Option<WorkspaceEdit>> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let line_index = world.analysis().file_line_index(file_id);
@@ -498,7 +479,7 @@ pub fn handle_rename(
         return Ok(None);
     }
 
-    let refs = world.analysis().find_all_refs(file_id, offset, &token);
+    let refs = world.analysis().find_all_refs(file_id, offset)?;
     if refs.is_empty() {
         return Ok(None);
     }
@@ -525,13 +506,12 @@ pub fn handle_rename(
 pub fn handle_references(
     world: ServerWorld,
     params: req::ReferenceParams,
-    token: JobToken,
 ) -> Result<Option<Vec<Location>>> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let line_index = world.analysis().file_line_index(file_id);
     let offset = params.position.conv_with(&line_index);
 
-    let refs = world.analysis().find_all_refs(file_id, offset, &token);
+    let refs = world.analysis().find_all_refs(file_id, offset)?;
 
     Ok(Some(refs.into_iter()
         .filter_map(|r| to_location(r.0, r.1, &world, &line_index).ok())
@@ -541,16 +521,15 @@ pub fn handle_references(
 pub fn handle_code_action(
     world: ServerWorld,
     params: req::CodeActionParams,
-    _token: JobToken,
 ) -> Result<Option<CodeActionResponse>> {
     let file_id = params.text_document.try_conv_with(&world)?;
     let line_index = world.analysis().file_line_index(file_id);
     let range = params.range.conv_with(&line_index);
 
-    let assists = world.analysis().assists(file_id, range).into_iter();
+    let assists = world.analysis().assists(file_id, range)?.into_iter();
     let fixes = world
         .analysis()
-        .diagnostics(file_id)
+        .diagnostics(file_id)?
         .into_iter()
         .filter_map(|d| Some((d.range, d.fix?)))
         .filter(|(range, _fix)| contains_offset_nonstrict(*range, range.start()))
@@ -579,7 +558,7 @@ pub fn publish_diagnostics(
     let line_index = world.analysis().file_line_index(file_id);
     let diagnostics = world
         .analysis()
-        .diagnostics(file_id)
+        .diagnostics(file_id)?
         .into_iter()
         .map(|d| Diagnostic {
             range: d.range.conv_with(&line_index),
@@ -600,19 +579,20 @@ pub fn publish_decorations(
     let uri = world.file_id_to_uri(file_id)?;
     Ok(req::PublishDecorationsParams {
         uri,
-        decorations: highlight(&world, file_id),
+        decorations: highlight(&world, file_id)?,
     })
 }
 
-fn highlight(world: &ServerWorld, file_id: FileId) -> Vec<Decoration> {
+fn highlight(world: &ServerWorld, file_id: FileId) -> Result<Vec<Decoration>> {
     let line_index = world.analysis().file_line_index(file_id);
-    world
+    let res = world
         .analysis()
-        .highlight(file_id)
+        .highlight(file_id)?
         .into_iter()
         .map(|h| Decoration {
             range: h.range.conv_with(&line_index),
             tag: h.tag,
         })
-        .collect()
+        .collect();
+    Ok(res)
 }
diff --git a/crates/ra_lsp_server/src/main_loop/mod.rs b/crates/ra_lsp_server/src/main_loop/mod.rs
index 165f2e78f..b35ebd38b 100644
--- a/crates/ra_lsp_server/src/main_loop/mod.rs
+++ b/crates/ra_lsp_server/src/main_loop/mod.rs
@@ -8,9 +8,9 @@ use gen_lsp_server::{
     handle_shutdown, ErrorCode, RawMessage, RawNotification, RawRequest, RawResponse,
 };
 use languageserver_types::NumberOrString;
-use ra_analysis::{FileId, JobHandle, JobToken, LibraryData};
+use ra_analysis::{FileId, LibraryData};
 use rayon::{self, ThreadPool};
-use rustc_hash::FxHashMap;
+use rustc_hash::FxHashSet;
 use serde::{de::DeserializeOwned, Serialize};
 
 use crate::{
@@ -47,7 +47,7 @@ pub fn main_loop(
     info!("server initialized, serving requests");
     let mut state = ServerWorldState::new();
 
-    let mut pending_requests = FxHashMap::default();
+    let mut pending_requests = FxHashSet::default();
     let mut subs = Subscriptions::new();
     let main_res = main_loop_inner(
         internal_mode,
@@ -92,7 +92,7 @@ fn main_loop_inner(
     fs_worker: Worker<PathBuf, (PathBuf, Vec<FileEvent>)>,
     ws_worker: Worker<PathBuf, Result<CargoWorkspace>>,
     state: &mut ServerWorldState,
-    pending_requests: &mut FxHashMap<u64, JobHandle>,
+    pending_requests: &mut FxHashSet<u64>,
     subs: &mut Subscriptions,
 ) -> Result<()> {
     let (libdata_sender, libdata_receiver) = unbounded();
@@ -204,14 +204,13 @@ fn main_loop_inner(
 fn on_task(
     task: Task,
     msg_sender: &Sender<RawMessage>,
-    pending_requests: &mut FxHashMap<u64, JobHandle>,
+    pending_requests: &mut FxHashSet<u64>,
 ) {
     match task {
         Task::Respond(response) => {
-            if let Some(handle) = pending_requests.remove(&response.id) {
-                assert!(handle.has_completed());
+            if pending_requests.remove(&response.id) {
+                msg_sender.send(RawMessage::Response(response))
             }
-            msg_sender.send(RawMessage::Response(response))
         }
         Task::Notify(n) => msg_sender.send(RawMessage::Notification(n)),
     }
@@ -219,7 +218,7 @@ fn on_task(
 
 fn on_request(
     world: &mut ServerWorldState,
-    pending_requests: &mut FxHashMap<u64, JobHandle>,
+    pending_requests: &mut FxHashSet<u64>,
     pool: &ThreadPool,
     sender: &Sender<Task>,
     req: RawRequest,
@@ -253,8 +252,8 @@ fn on_request(
         .on::<req::References>(handlers::handle_references)?
         .finish();
     match req {
-        Ok((id, handle)) => {
-            let inserted = pending_requests.insert(id, handle).is_none();
+        Ok(id) => {
+            let inserted = pending_requests.insert(id);
             assert!(inserted, "duplicate request: {}", id);
             Ok(None)
         }
@@ -265,7 +264,7 @@ fn on_request(
 fn on_notification(
     msg_sender: &Sender<RawMessage>,
     state: &mut ServerWorldState,
-    pending_requests: &mut FxHashMap<u64, JobHandle>,
+    pending_requests: &mut FxHashSet<u64>,
     subs: &mut Subscriptions,
     not: RawNotification,
 ) -> Result<()> {
@@ -277,9 +276,7 @@ fn on_notification(
                     panic!("string id's not supported: {:?}", id);
                 }
             };
-            if let Some(handle) = pending_requests.remove(&id) {
-                handle.cancel();
-            }
+            pending_requests.remove(&id);
             return Ok(());
         }
         Err(not) => not,
@@ -336,7 +333,7 @@ fn on_notification(
 
 struct PoolDispatcher<'a> {
     req: Option<RawRequest>,
-    res: Option<(u64, JobHandle)>,
+    res: Option<u64>,
     pool: &'a ThreadPool,
     world: &'a ServerWorldState,
     sender: &'a Sender<Task>,
@@ -345,7 +342,7 @@ struct PoolDispatcher<'a> {
 impl<'a> PoolDispatcher<'a> {
     fn on<'b, R>(
         &'b mut self,
-        f: fn(ServerWorld, R::Params, JobToken) -> Result<R::Result>,
+        f: fn(ServerWorld, R::Params) -> Result<R::Result>,
     ) -> Result<&'b mut Self>
     where
         R: req::Request,
@@ -358,11 +355,10 @@ impl<'a> PoolDispatcher<'a> {
         };
         match req.cast::<R>() {
             Ok((id, params)) => {
-                let (handle, token) = JobHandle::new();
                 let world = self.world.snapshot();
                 let sender = self.sender.clone();
                 self.pool.spawn(move || {
-                    let resp = match f(world, params, token) {
+                    let resp = match f(world, params) {
                         Ok(resp) => RawResponse::ok::<R>(id, &resp),
                         Err(e) => {
                             RawResponse::err(id, ErrorCode::InternalError as i32, e.to_string())
@@ -371,14 +367,14 @@ impl<'a> PoolDispatcher<'a> {
                     let task = Task::Respond(resp);
                     sender.send(task);
                 });
-                self.res = Some((id, handle));
+                self.res = Some(id);
             }
             Err(req) => self.req = Some(req),
         }
         Ok(self)
     }
 
-    fn finish(&mut self) -> ::std::result::Result<(u64, JobHandle), RawRequest> {
+    fn finish(&mut self) -> ::std::result::Result<u64, RawRequest> {
         match (self.res.take(), self.req.take()) {
             (Some(res), None) => Ok(res),
             (None, Some(req)) => Err(req),
diff --git a/crates/ra_lsp_server/src/path_map.rs b/crates/ra_lsp_server/src/path_map.rs
index 585013acd..d32829382 100644
--- a/crates/ra_lsp_server/src/path_map.rs
+++ b/crates/ra_lsp_server/src/path_map.rs
@@ -1,9 +1,9 @@
+use std::path::{Component, Path, PathBuf};
+
 use im;
 use ra_analysis::{FileId, FileResolver};
 use relative_path::RelativePath;
 
-use std::path::{Component, Path, PathBuf};
-
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Root {
     Workspace,
diff --git a/crates/ra_lsp_server/src/project_model.rs b/crates/ra_lsp_server/src/project_model.rs
index d170ceb73..04e2ef9c8 100644
--- a/crates/ra_lsp_server/src/project_model.rs
+++ b/crates/ra_lsp_server/src/project_model.rs
@@ -1,9 +1,9 @@
+use std::path::{Path, PathBuf};
+
 use cargo_metadata::{metadata_run, CargoOpt};
 use ra_syntax::SmolStr;
 use rustc_hash::{FxHashMap, FxHashSet};
 
-use std::path::{Path, PathBuf};
-
 use crate::{
     thread_watcher::{ThreadWatcher, Worker},
     Result,
diff --git a/crates/ra_lsp_server/src/thread_watcher.rs b/crates/ra_lsp_server/src/thread_watcher.rs
index 67952eb74..51b35fa66 100644
--- a/crates/ra_lsp_server/src/thread_watcher.rs
+++ b/crates/ra_lsp_server/src/thread_watcher.rs
@@ -1,8 +1,9 @@
-use crate::Result;
+use std::thread;
+
 use crossbeam_channel::{bounded, unbounded, Receiver, Sender};
 use drop_bomb::DropBomb;
 
-use std::thread;
+use crate::Result;
 
 pub struct Worker<I, O> {
     pub inp: Sender<I>,