Reverting 17770 - right, that is what "map view...

Reverting 17770 - right, that is what "map view" means.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/library/scala/collection/generic/MapTemplate.scala b/src/library/scala/collection/generic/MapTemplate.scala
index 4f4830d65c..a3260cc9b0 100644
--- a/src/library/scala/collection/generic/MapTemplate.scala
+++ b/src/library/scala/collection/generic/MapTemplate.scala
@@ -162,7 +162,12 @@ self =>
   /** A map view consisting only of those key value pairs where the key satisfies a given
    *  predicate `p`.
    */
-  def filterKeys(p: A => Boolean): This = this filter (kv => p(kv._1))
+  def filterKeys(p: A => Boolean) = new DefaultMap[A, B] {
+    override def foreach[C](f: ((A, B)) => C): Unit = for (kv <- self) if (p(kv._1)) f(kv)
+    def elements = self.elements.filter(kv => p(kv._1))
+    override def contains(key: A) = self.contains(key) && p(key)
+    def get(key: A) = if (!p(key)) None else self.get(key)
+  }
 
   /** A map view resulting from applying a given function `f` to each value.
    */