Introduce Cloneable trait

collections/src/main/scala/strawman/collection/mutable/Cloneable.scala

@@ -0,0 +1,13 @@
+package strawman.collection.mutable
+
+import scala.AnyRef
+
+/** A trait for cloneable collections.
+  *
+  *  @since 2.8
+  *
+  *  @tparam A    Type of the collection, covariant and with reference types as upperbound.
+  */
+trait Cloneable[+A <: AnyRef] extends scala.Cloneable {
+  override def clone(): A = super.clone().asInstanceOf[A]
+}

collections/src/main/scala/strawman/collection/mutable/Map.scala

@@ -10,8 +10,7 @@ import scala.{Boolean, None, Option, Some, Unit, `inline`, deprecated}
 trait Map[K, V]
   extends Iterable[(K, V)]
     with collection.Map[K, V]
-    with MapOps[K, V, Map, Map[K, V]]
-    with Shrinkable[K] {
+    with MapOps[K, V, Map, Map[K, V]] {
 
   /*
   //TODO consider keeping `remove` because it returns the removed entry
@@ -53,10 +52,11 @@ trait Map[K, V]
 trait MapOps[K, V, +CC[X, Y] <: MapOps[X, Y, CC, _], +C <: MapOps[K, V, CC, C]]
   extends IterableOps[(K, V), Iterable, C]
     with collection.MapOps[K, V, CC, C]
+    with Cloneable[C]
     with Growable[(K, V)]
     with Shrinkable[K] {
 
-  def iterableFactory = Iterable
+  def iterableFactory: IterableFactory[Iterable] = Iterable
 
   /** Adds a new key/value pair to this map and optionally returns previously bound value.
     *  If the map already contains a

collections/src/main/scala/strawman/collection/mutable/Seq.scala

@@ -24,7 +24,8 @@ object Seq extends SeqFactory.Delegate[Seq](ArrayBuffer)
   */
 trait SeqOps[A, +CC[X] <: Seq[X], +C <: Seq[A]]
   extends IterableOps[A, CC, C]
-    with collection.SeqOps[A, CC, C] {
+    with collection.SeqOps[A, CC, C]
+    with Cloneable[C] {
 
   override def clone(): C = {
     val b = newSpecificBuilder()

collections/src/main/scala/strawman/collection/mutable/Set.scala

@@ -18,6 +18,7 @@ trait Set[A]
 trait SetOps[A, +CC[X], +C <: SetOps[A, CC, C]]
   extends IterableOps[A, CC, C]
     with collection.SetOps[A, CC, C]
+    with Cloneable[C]
     with Growable[A]
     with Shrinkable[A] {