Fix for view isEmpty.

Views have been inheriting the very inefficient isEmpty
from Traversable, and since isEmpty is not specifically
forwarded to the underlying collections, views miss out on all
the important optimizations in those collections which tend to
be implemented via method override.  Not to mention, they miss
out on correctness, because calling foreach has a habit of
forcing the first element of the view.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/library/scala/collection/IterableLike.scala b/src/library/scala/collection/IterableLike.scala
index 2e9599058f..ac6d754f9e 100644
--- a/src/library/scala/collection/IterableLike.scala
+++ b/src/library/scala/collection/IterableLike.scala
@@ -171,7 +171,7 @@ self =>
    *          fewer elements than size.
    */
   def sliding(size: Int): Iterator[Repr] = sliding(size, 1)
-  
+
   /** Groups elements in fixed size blocks by passing a "sliding window"
    *  over them (as opposed to partitioning them, as is done in grouped.)
    *  @see [[scala.collection.Iterator]], method `sliding`
@@ -293,6 +293,7 @@ self =>
 
   override /*TraversableLike*/ def view = new IterableView[A, Repr] {
     protected lazy val underlying = self.repr
+    override def isEmpty = self.isEmpty
     override def iterator = self.iterator
   }