Fixes SI-6150 - backport to 2.10.x branch.

2 files changed, 24 insertions, 6 deletions

diff --git a/src/library/scala/collection/generic/GenTraversableFactory.scala b/src/library/scala/collection/generic/GenTraversableFactory.scala
index d5edf5961e..a43862abaf 100644
--- a/src/library/scala/collection/generic/GenTraversableFactory.scala
+++ b/src/library/scala/collection/generic/GenTraversableFactory.scala
@@ -36,15 +36,12 @@ import scala.language.higherKinds
  *    @see GenericCanBuildFrom
  */
 abstract class GenTraversableFactory[CC[X] <: GenTraversable[X] with GenericTraversableTemplate[X, CC]]
-  extends GenericCompanion[CC] {
+extends GenericCompanion[CC] {
 
-  // A default implementation of GenericCanBuildFrom which can be cast
-  // to whatever is desired.
-  private class ReusableCBF extends GenericCanBuildFrom[Nothing] {
+  private[this] val ReusableCBFInstance: GenericCanBuildFrom[Nothing] = new GenericCanBuildFrom[Nothing] {
     override def apply() = newBuilder[Nothing]
   }
-  // Working around SI-4789 by using a lazy val instead of an object.
-  lazy val ReusableCBF: GenericCanBuildFrom[Nothing] = new ReusableCBF
+  def ReusableCBF: GenericCanBuildFrom[Nothing] = ReusableCBFInstance
 
   /** A generic implementation of the `CanBuildFrom` trait, which forwards
    *  all calls to `apply(from)` to the `genericBuilder` method of
diff --git a/src/library/scala/collection/generic/IndexedSeqFactory.scala b/src/library/scala/collection/generic/IndexedSeqFactory.scala
new file mode 100644
index 0000000000..200d033c2d
--- /dev/null
+++ b/src/library/scala/collection/generic/IndexedSeqFactory.scala
@@ -0,0 +1,21 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003-2011, LAMP/EPFL             **
+**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+\*                                                                      */
+
+package scala.collection
+package generic
+
+import language.higherKinds
+
+/** A template for companion objects of IndexedSeq and subclasses thereof.
+ *
+ *  @since 2.10
+ */
+abstract class IndexedSeqFactory[CC[X] <: IndexedSeq[X] with GenericTraversableTemplate[X, CC]] extends SeqFactory[CC] {
+  override def ReusableCBF: GenericCanBuildFrom[Nothing] =
+    scala.collection.IndexedSeq.ReusableCBF.asInstanceOf[GenericCanBuildFrom[Nothing]]
+}