Optimized toArray for ArrayOps and WrappedArrays.

5 files changed, 35 insertions, 6 deletions

diff --git a/src/library/scala/collection/SeqView.scala b/src/library/scala/collection/SeqView.scala
index 61443b3b90..79d50f1de6 100644
--- a/src/library/scala/collection/SeqView.scala
+++ b/src/library/scala/collection/SeqView.scala
@@ -21,6 +21,8 @@ import TraversableView.NoBuilder
  */
 trait SeqView[+A, +Coll] extends SeqViewLike[A, Coll, SeqView[A, Coll]]
 
+/** $factoryInfo
+ */
 object SeqView {
   type Coll = TraversableView[_, C] forSome {type C <: Traversable[_]}
   implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, SeqView[A, Seq[_]]] =
diff --git a/src/library/scala/collection/mutable/ArrayOps.scala b/src/library/scala/collection/mutable/ArrayOps.scala
index 61fcc77e14..553461c805 100644
--- a/src/library/scala/collection/mutable/ArrayOps.scala
+++ b/src/library/scala/collection/mutable/ArrayOps.scala
@@ -24,6 +24,12 @@ abstract class ArrayOps[T] extends ArrayLike[T, Array[T]] {
       ClassManifest.fromClass(
         repr.getClass.getComponentType.getComponentType.asInstanceOf[Predef.Class[U]]))
 
+  override def toArray[U >: T : ClassManifest]: Array[U] =
+    if (implicitly[ClassManifest[U]].erasure eq repr.getClass.getComponentType)
+      repr.asInstanceOf[Array[U]]
+    else
+      super.toArray[U]
+
   /** Flattens a two-dimensional array by concatenating all its rows
    *  into a single array
    */
diff --git a/src/library/scala/collection/mutable/IndexedSeqView.scala b/src/library/scala/collection/mutable/IndexedSeqView.scala
index c6c92db1e7..d870b762d3 100644
--- a/src/library/scala/collection/mutable/IndexedSeqView.scala
+++ b/src/library/scala/collection/mutable/IndexedSeqView.scala
@@ -91,9 +91,22 @@ self =>
   override def reverse: IndexedSeqView[A, Coll] = newReversed.asInstanceOf[IndexedSeqView[A, Coll]]
 }
 
-/*
- * object IndexedSeqView {
-  type Coll = TraversableView[_, C] forSome { type C <: scala.collection.Traversable[_] }
-  implicit def canBuildFrom[A]: CanBuildFrom[IndexedSeq[_], A, IndexedSeqView[A], Coll] = new CanBuildFrom[mutable.IndexedSeq[_], A, IndexedSeqView[A], Coll] { : Coll) = new NoBuilder }
+/** $factoryInfo
+ * Note that the canBuildFrom factories yield SeqViews, not IndexedSewqViews.
+ * This is intentional, because not all operations yield again a mutable.IndexedSeqView.
+ * For instance, map just gives a SeqView, which reflects the fact that
+ * map cannot do its work and maintain a pointer into the original indexed sequence.
+ */
+object IndexedSeqView {
+  type Coll = TraversableView[_, C] forSome {type C <: Traversable[_]}
+  implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, SeqView[A, Seq[_]]] =
+    new CanBuildFrom[Coll, A, SeqView[A, Seq[_]]] {
+      def apply(from: Coll) = new NoBuilder
+      def apply() = new NoBuilder
+    }
+  implicit def arrCanBuildFrom[A]: CanBuildFrom[TraversableView[_, Array[_]], A, SeqView[A, Array[A]]] =
+    new CanBuildFrom[TraversableView[_, Array[_]], A, SeqView[A, Array[A]]] {
+      def apply(from: TraversableView[_, Array[_]]) = new NoBuilder
+      def apply() = new NoBuilder
+    }
 }
-*/
diff --git a/src/library/scala/collection/mutable/WrappedArray.scala b/src/library/scala/collection/mutable/WrappedArray.scala
index 6652f5e40a..10117a1086 100644
--- a/src/library/scala/collection/mutable/WrappedArray.scala
+++ b/src/library/scala/collection/mutable/WrappedArray.scala
@@ -41,6 +41,13 @@ abstract class WrappedArray[T] extends IndexedSeq[T] with ArrayLike[T, WrappedAr
 
   /** The underlying array */
   def array: Array[T]
+
+  override def toArray[U >: T : ClassManifest]: Array[U] =
+    if (implicitly[ClassManifest[U]].erasure eq array.getClass.getComponentType)
+      array.asInstanceOf[Array[U]]
+    else
+      super.toArray[U]
+
   override def stringPrefix = "WrappedArray"
 
   /** Clones this object, including the underlying Array. */
diff --git a/src/library/scala/runtime/ScalaRunTime.scala b/src/library/scala/runtime/ScalaRunTime.scala
index 2970cf1980..dffebfc892 100644
--- a/src/library/scala/runtime/ScalaRunTime.scala
+++ b/src/library/scala/runtime/ScalaRunTime.scala
@@ -12,7 +12,7 @@
 package scala.runtime
 
 import scala.reflect.ClassManifest
-import scala.collection.{ Seq, IndexedSeq }
+import scala.collection.{ Seq, IndexedSeq, TraversableView }
 import scala.collection.mutable.WrappedArray
 import scala.collection.immutable.{ List, Stream, Nil, :: }
 import scala.xml.{ Node, MetaData }
@@ -240,6 +240,7 @@ object ScalaRunTime {
       // Not to mention MetaData extends Iterable[MetaData]
       case x: MetaData              => x toString
       case x: AnyRef if isArray(x)  => WrappedArray make x map inner mkString ("Array(", ", ", ")")
+      case x: TraversableView[_, _] => x.toString
       case x: Traversable[_] if !x.hasDefiniteSize => x.toString
       case x: Traversable[_]        =>
         // Some subclasses of AbstractFile implement Iterable, then throw an