Fixed problem discovered by Paul that views do ...

Fixed problem discovered by Paul that views do not support a filter in
for expressions. review by extempore.

3 files changed, 17 insertions, 3 deletions

diff --git a/src/library/scala/collection/TraversableLike.scala b/src/library/scala/collection/TraversableLike.scala
index 71e9b0f0e9..04d9002eae 100644
--- a/src/library/scala/collection/TraversableLike.scala
+++ b/src/library/scala/collection/TraversableLike.scala
@@ -86,7 +86,9 @@ import immutable.{List, Stream, Nil, ::}
  *
  *    Note: will not terminate for infinite-sized collections.
  */
-trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr] with TraversableOnce[A] {
+trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr]
+                                    with FilterMonadic[A, Repr]
+                                    with TraversableOnce[A] {
   self =>
 
   import Traversable.breaks._
@@ -754,12 +756,12 @@ trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr] with Traversable
    *             All these operations apply to those elements of this $coll which
    *             satisfy the predicate `p`.
    */
-  def withFilter(p: A => Boolean): WithFilter = new WithFilter(p)
+  def withFilter(p: A => Boolean): FilterMonadic[A, Repr] = new WithFilter(p)
 
   /** A class supporting filtered operations. Instances of this class are returned by
    *  method `withFilter`.
    */
-  class WithFilter(p: A => Boolean) {
+  class WithFilter(p: A => Boolean) extends FilterMonadic[A, Repr] {
 
     /** Builds a new collection by applying a function to all elements of the
      *  outer $coll containing this `WithFilter` instance that satisfy predicate `p`.
diff --git a/src/library/scala/collection/TraversableViewLike.scala b/src/library/scala/collection/TraversableViewLike.scala
index ae3f6c0e93..7b443e54b8 100644
--- a/src/library/scala/collection/TraversableViewLike.scala
+++ b/src/library/scala/collection/TraversableViewLike.scala
@@ -199,6 +199,7 @@ self =>
   }
 
   override def filter(p: A => Boolean): This = newFiltered(p).asInstanceOf[This]
+  override def withFilter(p: A => Boolean): This = newFiltered(p).asInstanceOf[This]
   override def partition(p: A => Boolean): (This, This) = (filter(p), filter(!p(_)))
   override def init: This = newSliced(0, size - 1).asInstanceOf[This]
   override def drop(n: Int): This = newSliced(n max 0, Int.MaxValue).asInstanceOf[This]
diff --git a/src/library/scala/collection/generic/FilterMonadic.scala b/src/library/scala/collection/generic/FilterMonadic.scala
new file mode 100755
index 0000000000..abf2e0355d
--- /dev/null
+++ b/src/library/scala/collection/generic/FilterMonadic.scala
@@ -0,0 +1,11 @@
+package scala.collection.generic
+
+/** A template trait that contains just the `map`, `flatMap`, `foreach` and `withFilter` methods
+ *  of trait `TraverableLike`.
+ */
+trait FilterMonadic[+A, +Repr] {
+  def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That
+  def flatMap[B, That](f: A => Traversable[B])(implicit bf: CanBuildFrom[Repr, B, That]): That
+  def foreach[U](f: A => U): Unit
+  def withFilter(p: A => Boolean): FilterMonadic[A, Repr]
+}