Separate option Ordering into a trait so it can...

Separate option Ordering into a trait so it can be reused. Closes #3539,
no review.

1 files changed, 10 insertions, 8 deletions

diff --git a/src/library/scala/math/Ordering.scala b/src/library/scala/math/Ordering.scala
index 4527e18338..fdfc4915d9 100644
--- a/src/library/scala/math/Ordering.scala
+++ b/src/library/scala/math/Ordering.scala
@@ -204,15 +204,17 @@ object Ordering extends LowPriorityOrderingImplicits {
   }
   implicit object String extends StringOrdering
 
-  implicit def Option[T](implicit ord: Ordering[T]) : Ordering[Option[T]] =
-    new Ordering[Option[T]] {
-      def compare(x : Option[T], y : Option[T]) = (x, y) match {
-        case (None, None) => 0
-        case (None, _) => -1
-        case (_, None) => 1
-        case (Some(x), Some(y)) => ord.compare(x, y)
-      }
+  trait OptionOrdering[T] extends Ordering[Option[T]] {
+    def optionOrdering: Ordering[T]
+    def compare(x: Option[T], y: Option[T]) = (x, y) match {
+      case (None, None)       => 0
+      case (None, _)          => -1
+      case (_, None)          => 1
+      case (Some(x), Some(y)) => optionOrdering.compare(x, y)
     }
+  }
+  implicit def Option[T](implicit ord: Ordering[T]): Ordering[Option[T]] =
+    new OptionOrdering[T] { val optionOrdering = ord }
 
   implicit def Iterable[T](implicit ord: Ordering[T]): Ordering[Iterable[T]] =
     new Ordering[Iterable[T]] {