Merge pull request #1097 from rklaehn/SI-6198

Si 6198

2 files changed, 14 insertions, 12 deletions

diff --git a/src/library/scala/collection/immutable/HashSet.scala b/src/library/scala/collection/immutable/HashSet.scala
index c60fdc3bf1..7171e32ccc 100644
--- a/src/library/scala/collection/immutable/HashSet.scala
+++ b/src/library/scala/collection/immutable/HashSet.scala
@@ -151,10 +151,12 @@ object HashSet extends ImmutableSetFactory[HashSet] {
     override def removed0(key: A, hash: Int, level: Int): HashSet[A] =
       if (hash == this.hash) {
         val ks1 = ks - key
-        if (!ks1.isEmpty)
-          new HashSetCollision1(hash, ks1)
-        else
+        if(ks1.isEmpty)
           HashSet.empty[A]
+        else if(ks1.tail.isEmpty)
+          new HashSet1(ks1.head, hash)
+        else
+          new HashSetCollision1(hash, ks1)
       } else this
 
     override def iterator: Iterator[A] = ks.iterator
diff --git a/src/library/scala/collection/immutable/ListSet.scala b/src/library/scala/collection/immutable/ListSet.scala
index ce3abaacb7..4dd0d62fc0 100644
--- a/src/library/scala/collection/immutable/ListSet.scala
+++ b/src/library/scala/collection/immutable/ListSet.scala
@@ -116,8 +116,8 @@ class ListSet[A] extends AbstractSet[A]
     def hasNext = that.nonEmpty
     def next: A =
       if (hasNext) {
-        val res = that.elem
-        that = that.next
+        val res = that.head
+        that = that.tail
         res
       }
       else Iterator.empty.next
@@ -126,18 +126,18 @@ class ListSet[A] extends AbstractSet[A]
   /**
    *  @throws Predef.NoSuchElementException
    */
-  protected def elem: A = throw new NoSuchElementException("Set has no elements");
+  override def head: A = throw new NoSuchElementException("Set has no elements");
 
   /**
    *  @throws Predef.NoSuchElementException
    */
-  protected def next: ListSet[A] = throw new NoSuchElementException("Next of an empty set");
+  override def tail: ListSet[A] = throw new NoSuchElementException("Next of an empty set");
 
   override def stringPrefix = "ListSet"
 
   /** Represents an entry in the `ListSet`.
    */
-  protected class Node(override protected val elem: A) extends ListSet[A] with Serializable {
+  protected class Node(override val head: A) extends ListSet[A] with Serializable {
     override private[ListSet] def unchecked_outer = self
 
     /** Returns the number of elements in this set.
@@ -162,7 +162,7 @@ class ListSet[A] extends AbstractSet[A]
      */
     override def contains(e: A) = containsInternal(this, e)
     @tailrec private def containsInternal(n: ListSet[A], e: A): Boolean =
-      !n.isEmpty && (n.elem == e || containsInternal(n.unchecked_outer, e))
+      !n.isEmpty && (n.head == e || containsInternal(n.unchecked_outer, e))
 
     /** This method creates a new set with an additional element.
      */
@@ -170,10 +170,10 @@ class ListSet[A] extends AbstractSet[A]
 
     /** `-` can be used to remove a single element from a set.
      */
-    override def -(e: A): ListSet[A] = if (e == elem) self else {
-      val tail = self - e; new tail.Node(elem)
+    override def -(e: A): ListSet[A] = if (e == head) self else {
+      val tail = self - e; new tail.Node(head)
     }
 
-    override protected def next: ListSet[A] = self
+    override def tail: ListSet[A] = self
   }
 }