Modified SI-6150 fix to use intended ReusableCBF.

I also realized it didn't have to be lazy, and made it so.

4 files changed, 12 insertions, 10 deletions

diff --git a/src/library/scala/collection/IndexedSeq.scala b/src/library/scala/collection/IndexedSeq.scala
index 4d1758fdd3..39be1f7a9e 100644
--- a/src/library/scala/collection/IndexedSeq.scala
+++ b/src/library/scala/collection/IndexedSeq.scala
@@ -29,9 +29,12 @@ trait IndexedSeq[+A] extends Seq[A]
  *  @define Coll `IndexedSeq`
  */
 object IndexedSeq extends SeqFactory[IndexedSeq] {
-  override lazy val ReusableCBF: GenericCanBuildFrom[Nothing] = new ReusableCBF
-  
-  implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, IndexedSeq[A]] = IndexedSeq.ReusableCBF.asInstanceOf[GenericCanBuildFrom[A]]
+  override val ReusableCBF: GenericCanBuildFrom[Nothing] = new GenericCanBuildFrom[Nothing] {
+    override def apply() = newBuilder[Nothing]
+  }
+  implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, IndexedSeq[A]] =
+    ReusableCBF.asInstanceOf[GenericCanBuildFrom[A]]
+
   def newBuilder[A]: Builder[A, IndexedSeq[A]] = immutable.IndexedSeq.newBuilder[A]
 }
 
diff --git a/src/library/scala/collection/generic/GenTraversableFactory.scala b/src/library/scala/collection/generic/GenTraversableFactory.scala
index 3d5306621a..076f555506 100644
--- a/src/library/scala/collection/generic/GenTraversableFactory.scala
+++ b/src/library/scala/collection/generic/GenTraversableFactory.scala
@@ -40,11 +40,9 @@ abstract class GenTraversableFactory[CC[X] <: GenTraversable[X] with GenericTrav
 
   // A default implementation of GenericCanBuildFrom which can be cast
   // to whatever is desired.
-  private[collection] class ReusableCBF extends GenericCanBuildFrom[Nothing] {
+  val ReusableCBF: 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
 
   /** 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/immutable/IndexedSeq.scala b/src/library/scala/collection/immutable/IndexedSeq.scala
index 3abac932e6..68f642b558 100644
--- a/src/library/scala/collection/immutable/IndexedSeq.scala
+++ b/src/library/scala/collection/immutable/IndexedSeq.scala
@@ -36,6 +36,7 @@ object IndexedSeq extends SeqFactory[IndexedSeq] {
     def length = buf.length
     def apply(idx: Int) = buf.apply(idx)
   }
-  implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, IndexedSeq[A]] = IndexedSeq.ReusableCBF.asInstanceOf[GenericCanBuildFrom[A]]
+  implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, IndexedSeq[A]] =
+    scala.collection.IndexedSeq.ReusableCBF.asInstanceOf[GenericCanBuildFrom[A]]
   def newBuilder[A]: Builder[A, IndexedSeq[A]] = Vector.newBuilder[A]
 }
diff --git a/src/library/scala/collection/immutable/Vector.scala b/src/library/scala/collection/immutable/Vector.scala
index d0098e8420..f912285143 100644
--- a/src/library/scala/collection/immutable/Vector.scala
+++ b/src/library/scala/collection/immutable/Vector.scala
@@ -19,7 +19,7 @@ import scala.collection.parallel.immutable.ParVector
  */
 object Vector extends SeqFactory[Vector] {
   @inline implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, Vector[A]] =
-    IndexedSeq.ReusableCBF.asInstanceOf[CanBuildFrom[Coll, A, Vector[A]]]
+    scala.collection.IndexedSeq.ReusableCBF.asInstanceOf[GenericCanBuildFrom[A]]
   def newBuilder[A]: Builder[A, Vector[A]] = new VectorBuilder[A]
   private[immutable] val NIL = new Vector[Nothing](0, 0, 0)
   @inline override def empty[A]: Vector[A] = NIL
@@ -144,11 +144,11 @@ override def companion: GenericCompanion[Vector] = Vector
     if (bf eq IndexedSeq.ReusableCBF) updateAt(index, elem).asInstanceOf[That] // just ignore bf
     else super.updated(index, elem)(bf)
 
-  @inline override def +:[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Vector[A], B, That]): That = 
+  @inline override def +:[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Vector[A], B, That]): That =
     if (bf eq IndexedSeq.ReusableCBF) appendFront(elem).asInstanceOf[That] // just ignore bf
     else super.+:(elem)(bf)
 
-  @inline override def :+[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Vector[A], B, That]): That = 
+  @inline override def :+[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Vector[A], B, That]): That =
     if (bf eq IndexedSeq.ReusableCBF) appendBack(elem).asInstanceOf[That] // just ignore bf
     else super.:+(elem)(bf)