separated mutable and immutable maps

1 files changed, 1 insertions, 1 deletions

diff --git a/src/library/scala/collection/generic/TraversableView.scala b/src/library/scala/collection/generic/TraversableView.scala
index 939dc5b032..c89639bab1 100644
--- a/src/library/scala/collection/generic/TraversableView.scala
+++ b/src/library/scala/collection/generic/TraversableView.scala
@@ -19,7 +19,7 @@ trait TraversableView[+A, +Coll <: Traversable[_]] extends TraversableViewTempla
 
 object TraversableView {
   class NoBuilder[A] extends Builder[A, Nothing] {
-    def +=(elem: A) {}
+    def +=(elem: A): this.type = this
     def elements: Iterator[A] = Iterator.empty
     def result() = throw new UnsupportedOperationException("TraversableView.Builder.result")
     def clear() {}