1 files changed, 12 insertions, 3 deletions
diff --git a/src/library/scala/collection/SetLike.scala b/src/library/scala/collection/SetLike.scala
index f8ac1d754d..d03c808c2c 100644
--- a/src/library/scala/collection/SetLike.scala
+++ b/src/library/scala/collection/SetLike.scala
@@ -77,11 +77,20 @@ self =>
 
   protected[this] override def parCombiner = ParSet.newCombiner[A]
 
-  /* Overridden for efficiency. */
-  override def toSeq: Seq[A] = toBuffer[A]
+  // Default collection type appropriate for immutable collections; mutable collections override this
+  override def toSeq: Seq[A] = {
+    if (isEmpty) Vector.empty[A]
+    else {
+      val vb = Vector.newBuilder[A]
+      foreach(vb += _)
+      vb.result
+    }
+  }
+  
   override def toBuffer[A1 >: A]: mutable.Buffer[A1] = {
     val result = new mutable.ArrayBuffer[A1](size)
-    copyToBuffer(result)
+    // Faster to let the map iterate itself than to defer through copyToBuffer
+    foreach(result += _)
     result
   }