fixed #2500: refactoring collections so that a ...

fixed #2500: refactoring collections so that a `collection.{Map|SortedMap|SortedSet}` can be built from the corresponding collection (thus, do not require the immutable one)

pulling up newBuilder method from Immutable*Factory to *Factory, and
inheriting *Factory in scala.collection companion objects, instead of
the Immutable*Factory this way, you can, e.g., build a collection.Map
from a collection.Map (instead of requiring an immutable.Map)

1 files changed, 3 insertions, 3 deletions

diff --git a/src/library/scala/collection/generic/MapFactory.scala b/src/library/scala/collection/generic/MapFactory.scala
index 9e47412448..2476142ec7 100644
--- a/src/library/scala/collection/generic/MapFactory.scala
+++ b/src/library/scala/collection/generic/MapFactory.scala
@@ -12,7 +12,7 @@
 package scala.collection
 package generic
 
-import mutable.Builder
+import mutable.{Builder, MapBuilder}
 
 /** A template for companion objects of <code>mutable.Map</code> and
  *  subclasses thereof.
@@ -23,12 +23,12 @@ abstract class MapFactory[CC[A, B] <: Map[A, B] with MapLike[A, B, CC[A, B]]] {
 
   type Coll = CC[_, _]
 
-  def newBuilder[A, B]: Builder[(A, B), CC[A, B]]
-
   def empty[A, B]: CC[A, B]
 
   def apply[A, B](elems: (A, B)*): CC[A, B] = (newBuilder[A, B] ++= elems).result
 
+  def newBuilder[A, B]: Builder[(A, B), CC[A, B]] = new MapBuilder[A, B, CC[A, B]](empty[A, B])
+
   class MapCanBuildFrom[A, B] extends CanBuildFrom[Coll, (A, B), CC[A, B]] {
     def apply(from: Coll) = newBuilder[A, B]
     def apply() = newBuilder