separated mutable and immutable maps

1 files changed, 3 insertions, 3 deletions

diff --git a/src/library/scala/collection/mutable/SynchronizedQueue.scala b/src/library/scala/collection/mutable/SynchronizedQueue.scala
index 0b3f870a9f..7a803c5879 100644
--- a/src/library/scala/collection/mutable/SynchronizedQueue.scala
+++ b/src/library/scala/collection/mutable/SynchronizedQueue.scala
@@ -32,7 +32,7 @@ class SynchronizedQueue[A] extends Queue[A] {
    *
    *  @param  elem        the element to insert
    */
-  override def +=(elem: A): Unit = synchronized { super.+=(elem) }
+  override def +=(elem: A): this.type = synchronized[this.type] { super.+=(elem) }
 
   /** Adds all elements provided by an <code>Iterable</code> object
    *  at the end of the queue. The elements are prepended in the order they
@@ -40,7 +40,7 @@ class SynchronizedQueue[A] extends Queue[A] {
    *
    *  @param  iter        an iterable object
    */
-  override def ++=(iter: Traversable[A]): Unit = synchronized { super.++=(iter) }
+  override def ++=(iter: Traversable[A]): this.type = synchronized[this.type] { super.++=(iter) }
 
   /** Adds all elements provided by an iterator
    *  at the end of the queue. The elements are prepended in the order they
@@ -48,7 +48,7 @@ class SynchronizedQueue[A] extends Queue[A] {
    *
    *  @param  it        an iterator
    */
-  override def ++=(it: Iterator[A]): Unit = synchronized { super.++=(it) }
+  override def ++=(it: Iterator[A]): this.type = synchronized[this.type] { super.++=(it) }
 
   /** Adds all elements to the queue.
    *