Overrides immutable.{ Map, Set, Seq } to return...

Overrides immutable.{ Map, Set, Seq } to return self on
the corresponding toMap/toSet/toSeq.  Closes #3953, review
by prokopec.

3 files changed, 4 insertions, 0 deletions

diff --git a/src/library/scala/collection/immutable/Map.scala b/src/library/scala/collection/immutable/Map.scala
index 5a6b1be3d5..d345b89057 100644
--- a/src/library/scala/collection/immutable/Map.scala
+++ b/src/library/scala/collection/immutable/Map.scala
@@ -30,6 +30,8 @@ trait Map[A, +B] extends Iterable[(A, B)]
                     with MapLike[A, B, Map[A, B]] { self =>
 
   override def empty: Map[A, B] = Map.empty
+  override def toMap[T, U](implicit ev: (A, B) <:< (T, U)): immutable.Map[T, U] =
+    self.asInstanceOf[immutable.Map[T, U]]
 
   /** The same map with a given default function */
   def withDefault[B1 >: B](d: A => B1): immutable.Map[A, B1] = new Map.WithDefault[A, B1](this, d)
diff --git a/src/library/scala/collection/immutable/Seq.scala b/src/library/scala/collection/immutable/Seq.scala
index 18d3b9b263..5217b19097 100644
--- a/src/library/scala/collection/immutable/Seq.scala
+++ b/src/library/scala/collection/immutable/Seq.scala
@@ -26,6 +26,7 @@ trait Seq[+A] extends Iterable[A]
                       with GenericTraversableTemplate[A, Seq]
                       with SeqLike[A, Seq[A]] {
   override def companion: GenericCompanion[Seq] = Seq
+  override def toSeq: Seq[A] = this
 }
 
 /** $factoryInfo
diff --git a/src/library/scala/collection/immutable/Set.scala b/src/library/scala/collection/immutable/Set.scala
index ffd41752a4..d5520163d4 100644
--- a/src/library/scala/collection/immutable/Set.scala
+++ b/src/library/scala/collection/immutable/Set.scala
@@ -29,6 +29,7 @@ trait Set[A] extends Iterable[A]
                 with GenericSetTemplate[A, Set]
                 with SetLike[A, Set[A]] {
   override def companion: GenericCompanion[Set] = Set
+  override def toSet[B >: A]: Set[B] = this.asInstanceOf[Set[B]]
 }
 
 /** $factoryInfo