immutable.Map keySet returns immutable.Set.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/library/scala/collection/immutable/MapLike.scala b/src/library/scala/collection/immutable/MapLike.scala
index bbad195687..0e2723cf2b 100644
--- a/src/library/scala/collection/immutable/MapLike.scala
+++ b/src/library/scala/collection/immutable/MapLike.scala
@@ -50,8 +50,6 @@ trait MapLike[A, +B, +This <: MapLike[A, B, This] with Map[A, B]]
   extends scala.collection.MapLike[A, B, This]
 { self =>
 
-  import scala.collection.Traversable
-
   /** A new immutable map containing updating this map with a given key/value mapping.
    *  @param    key the key
    *  @param    value the value
@@ -110,6 +108,11 @@ trait MapLike[A, +B, +This <: MapLike[A, B, This] with Map[A, B]]
     def get(key: A) = self.get(key).map(f)
   }
 
+  /** Collects all keys of this map in a set.
+   *  @return  a set containing all keys of this map.
+   */
+  override def keySet: immutable.Set[A] = immutable.Set.empty ++ (this map (_._1))
+
   /** This function transforms all the values of mappings contained
    *  in this map with function `f`.
    *