4 files changed, 31 insertions, 29 deletions

diff --git a/crates/ra_analysis/src/imp.rs b/crates/ra_analysis/src/imp.rs
index d60fb8278..df5aacb2d 100644
--- a/crates/ra_analysis/src/imp.rs
+++ b/crates/ra_analysis/src/imp.rs
@@ -159,7 +159,7 @@ impl AnalysisImpl {
     }
     pub fn parent_module(&self, file_id: FileId) -> Cancelable<Vec<(FileId, FileSymbol)>> {
         let root = self.root(file_id);
-        let module_tree = root.module_tree();
+        let module_tree = root.module_tree()?;
         let res = module_tree
             .parent_modules(file_id)
             .iter()
@@ -177,8 +177,8 @@ impl AnalysisImpl {
             .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();
@@ -196,7 +196,7 @@ 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]
@@ -205,9 +205,9 @@ impl AnalysisImpl {
         &self,
         file_id: FileId,
         offset: TextUnit,
-    ) -> 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) {
@@ -223,10 +223,10 @@ impl AnalysisImpl {
                     },
                 ));
 
-                return vec;
+                return Ok(vec);
             } else {
                 // If that fails try the index based approach.
-                return self.index_resolve(name_ref);
+                return Ok(self.index_resolve(name_ref));
             }
         }
         if let Some(name) = find_node_at_offset::<ast::Name>(syntax, offset) {
@@ -250,11 +250,11 @@ impl AnalysisImpl {
                         })
                         .collect();
 
-                    return res;
+                    return Ok(res);
                 }
             }
         }
-        vec![]
+        Ok(vec![])
     }
 
     pub fn find_all_refs(&self, file_id: FileId, offset: TextUnit) -> Vec<(FileId, TextRange)> {
@@ -289,9 +289,9 @@ 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 +346,7 @@ impl AnalysisImpl {
             };
             res.push(diag)
         }
-        res
+        Ok(res)
     }
 
     pub fn assists(&self, file_id: FileId, range: TextRange) -> Vec<SourceChange> {
diff --git a/crates/ra_analysis/src/lib.rs b/crates/ra_analysis/src/lib.rs
index 8595d7e03..6ce32894a 100644
--- a/crates/ra_analysis/src/lib.rs
+++ b/crates/ra_analysis/src/lib.rs
@@ -37,7 +37,7 @@ pub use ra_editor::{
     RunnableKind, StructureNode,
 };
 
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct Cancel;
 
 pub type Cancelable<T> = Result<T, Cancel>;
@@ -231,8 +231,8 @@ impl Analysis {
         file_id: FileId,
         offset: TextUnit
     ) -> Cancelable<Vec<(FileId, FileSymbol)>> {
-        Ok(self.imp
-            .approximately_resolve_symbol(file_id, offset))
+        self.imp
+            .approximately_resolve_symbol(file_id, offset)
     }
     pub fn find_all_refs(&self, file_id: FileId, offset: TextUnit, ) -> Cancelable<Vec<(FileId, TextRange)>> {
         Ok(self.imp.find_all_refs(file_id, offset))
@@ -241,7 +241,7 @@ impl Analysis {
         self.imp.parent_module(file_id)
     }
     pub fn crate_for(&self, file_id: FileId) -> Cancelable<Vec<CrateId>> {
-        Ok(self.imp.crate_for(file_id))
+        self.imp.crate_for(file_id)
     }
     pub fn crate_root(&self, crate_id: CrateId) -> Cancelable<FileId> {
         Ok(self.imp.crate_root(crate_id))
@@ -262,7 +262,7 @@ impl Analysis {
         Ok(self.imp.assists(file_id, range))
     }
     pub fn diagnostics(&self, file_id: FileId) -> Cancelable<Vec<Diagnostic>> {
-        Ok(self.imp.diagnostics(file_id))
+        self.imp.diagnostics(file_id)
     }
     pub fn resolve_callable(
         &self,
diff --git a/crates/ra_analysis/src/module_map.rs b/crates/ra_analysis/src/module_map.rs
index b15432498..0c413becd 100644
--- a/crates/ra_analysis/src/module_map.rs
+++ b/crates/ra_analysis/src/module_map.rs
@@ -1,4 +1,5 @@
 use crate::{
+    Cancelable,
     db::SyntaxDatabase,
     descriptors::{ModuleDescriptor, ModuleTreeDescriptor},
     FileId,
@@ -8,30 +9,30 @@ 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>> {
     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>> {
     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..e950a75e2 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,
@@ -18,7 +19,7 @@ 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>>);
@@ -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 {
@@ -167,8 +168,8 @@ 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)