diff --git a/src/librustc/middle/pat_util.rs b/src/librustc/middle/pat_util.rs
index 0ffa5d7a5e3..ec7274a9b6d 100644
--- a/src/librustc/middle/pat_util.rs
+++ b/src/librustc/middle/pat_util.rs
@@ -228,7 +228,7 @@ pub fn necessary_variants(dm: &DefMap, pat: &hir::Pat) -> Vec<ast::NodeId> {
             hir::PatStruct(..) => {
                 match dm.borrow().get(&p.id) {
                     Some(&PathResolution { base_def: DefVariant(_, id, _), .. }) => {
-                        variants.push(id.node);
+                        variants.push(id.node); // XXX
                     }
                     _ => ()
                 }
diff --git a/src/librustc_resolve/record_exports.rs b/src/librustc_resolve/record_exports.rs
index 36ed2c14579..076b2fcc004 100644
--- a/src/librustc_resolve/record_exports.rs
+++ b/src/librustc_resolve/record_exports.rs
@@ -102,7 +102,7 @@ impl<'a, 'b, 'tcx> ExportRecorder<'a, 'b, 'tcx> {
         self.add_exports_for_module(&mut exports, module_);
         match module_.def_id.get() {
             Some(def_id) => {
-                self.export_map.insert(def_id.node, exports);
+                self.export_map.insert(def_id.node, exports); // XXX
                 debug!("(computing exports) writing exports for {} (some)",
                        def_id.node);
             }
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index 2c9f273d703..5811c3c72f7 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -558,7 +558,7 @@ fn is_param<'tcx>(tcx: &ty::ctxt<'tcx>,
     if let hir::TyPath(None, _) = ast_ty.node {
         let path_res = *tcx.def_map.borrow().get(&ast_ty.id).unwrap();
         match path_res.base_def {
-            def::DefSelfTy(Some(def_id), None) => {
+            def::DefSelfTy(Some(def_id), None) => { // XXX
                 path_res.depth == 0 && def_id.node == param_id
             }
             def::DefTyParam(_, _, def_id, _) => {