Merge pull request #3366 from Ichoran/issue/6457

SI-6457 ImmutableSetFactory.empty results in StackOverflowError

4 files changed, 8 insertions, 6 deletions

diff --git a/src/library/scala/collection/generic/ImmutableSetFactory.scala b/src/library/scala/collection/generic/ImmutableSetFactory.scala
index f4d4e061bb..a72caf2633 100644
--- a/src/library/scala/collection/generic/ImmutableSetFactory.scala
+++ b/src/library/scala/collection/generic/ImmutableSetFactory.scala
@@ -15,6 +15,7 @@ import scala.language.higherKinds
 
 abstract class ImmutableSetFactory[CC[X] <: immutable.Set[X] with SetLike[X, CC[X]]]
   extends SetFactory[CC] {
-
+  private[collection] def emptyInstance: CC[Any]
+  override def empty[A] = emptyInstance.asInstanceOf[CC[A]]
   def newBuilder[A]: Builder[A, CC[A]] = new SetBuilder[A, CC[A]](empty[A])
 }
diff --git a/src/library/scala/collection/immutable/HashSet.scala b/src/library/scala/collection/immutable/HashSet.scala
index 115be09502..d5787a660a 100644
--- a/src/library/scala/collection/immutable/HashSet.scala
+++ b/src/library/scala/collection/immutable/HashSet.scala
@@ -123,10 +123,10 @@ object HashSet extends ImmutableSetFactory[HashSet] {
 
   /** $setCanBuildFromInfo */
   implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, HashSet[A]] = setCanBuildFrom[A]
-  override def empty[A]: HashSet[A] = EmptyHashSet.asInstanceOf[HashSet[A]]
 
   private object EmptyHashSet extends HashSet[Any] { }
-
+  private[collection] def emptyInstance: HashSet[Any] = EmptyHashSet
+  
   // utility method to create a HashTrieSet from two leaf HashSets (HashSet1 or HashSetCollision1) with non-colliding hash code)
   private def makeHashTrieSet[A](hash0:Int, elem0:HashSet[A], hash1:Int, elem1:HashSet[A], level:Int) : HashTrieSet[A] = {
     val index0 = (hash0 >>> level) & 0x1f
diff --git a/src/library/scala/collection/immutable/ListSet.scala b/src/library/scala/collection/immutable/ListSet.scala
index 7ebaa26d26..1bb07eb02d 100644
--- a/src/library/scala/collection/immutable/ListSet.scala
+++ b/src/library/scala/collection/immutable/ListSet.scala
@@ -22,10 +22,11 @@ import mutable.{ ListBuffer, Builder }
 object ListSet extends ImmutableSetFactory[ListSet] {
   /** setCanBuildFromInfo */
   implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, ListSet[A]] = setCanBuildFrom[A]
-  override def empty[A] = EmptyListSet.asInstanceOf[ListSet[A]]
+
   override def newBuilder[A]: Builder[A, ListSet[A]] = new ListSetBuilder[A]
 
   private object EmptyListSet extends ListSet[Any] { }
+  private[collection] def emptyInstance: ListSet[Any] = EmptyListSet
 
   /** A custom builder because forgetfully adding elements one at
    *  a time to a list backed set puts the "squared" in N^2.  There is a
diff --git a/src/library/scala/collection/immutable/Set.scala b/src/library/scala/collection/immutable/Set.scala
index a888955bb2..e21a8dfa8a 100644
--- a/src/library/scala/collection/immutable/Set.scala
+++ b/src/library/scala/collection/immutable/Set.scala
@@ -53,8 +53,7 @@ trait Set[A] extends Iterable[A]
 object Set extends ImmutableSetFactory[Set] {
   /** $setCanBuildFromInfo */
   implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, Set[A]] = setCanBuildFrom[A]
-  override def empty[A]: Set[A] = EmptySet.asInstanceOf[Set[A]]
-
+  
   /** An optimized representation for immutable empty sets */
   private object EmptySet extends AbstractSet[Any] with Set[Any] with Serializable {
     override def size: Int = 0
@@ -64,6 +63,7 @@ object Set extends ImmutableSetFactory[Set] {
     def iterator: Iterator[Any] = Iterator.empty
     override def foreach[U](f: Any =>  U): Unit = {}
   }
+  private[collection] def emptyInstance: Set[Any] = EmptySet
 
   /** An optimized representation for immutable sets of size 1 */
   @SerialVersionUID(1233385750652442003L)