Merge pull request scala/scala#8672 from rorygraves/mike/2.12.x-HashMapLessTupling

remove tupling for foreach in keySet/values of immutable HashMap and TreeMap

Author: SethTisue

library/src/mima-filters/2.12.0.forwards.excludes

@@ -56,4 +56,7 @@ ProblemFilters.exclude[DirectMissingMethodProblem]("scala.collection.immutable.L
 ProblemFilters.exclude[DirectMissingMethodProblem]("scala.collection.immutable.HashMap#HashMap1.foreachEntry")
 ProblemFilters.exclude[DirectMissingMethodProblem]("scala.collection.immutable.HashMap#HashMapCollision1.foreachEntry")
 ProblemFilters.exclude[DirectMissingMethodProblem]("scala.util.hashing.MurmurHash3.product2Hash")
-ProblemFilters.exclude[DirectMissingMethodProblem]("scala.util.hashing.MurmurHash3.emptyMapHash")
+ProblemFilters.exclude[DirectMissingMethodProblem]("scala.util.hashing.MurmurHash3.emptyMapHash")
+
+ProblemFilters.exclude[MissingClassProblem]("scala.collection.immutable.HashMap$HashMapKeys")
+ProblemFilters.exclude[MissingClassProblem]("scala.collection.immutable.HashMap$HashMapValues")

library/src/scala/collection/immutable/HashMap.scala

@@ -139,6 +139,21 @@ sealed class HashMap[A, +B] extends AbstractMap[A, B]
 
   override def par = ParHashMap.fromTrie(this)
 
+  /* Override to avoid tuple allocation in foreach */
+  private[collection] class HashMapKeys extends ImmutableDefaultKeySet {
+    override def foreach[U](f: A => U) = foreachEntry((key, _) => f(key))
+    override lazy val hashCode = super.hashCode()
+  }
+  override def keySet: immutable.Set[A] = new HashMapKeys
+
+  /** The implementation class of the iterable returned by `values`.
+   */
+  private[collection] class HashMapValues extends DefaultValuesIterable {
+    override def foreach[U](f: B => U) = foreachEntry((_, value) => f(value))
+  }
+  override def values: scala.collection.Iterable[B] = new HashMapValues
+
+
 }
 
 /** $factoryInfo

library/src/scala/collection/immutable/TreeMap.scala

@@ -215,4 +215,11 @@ final class TreeMap[A, +B] private (tree: RB.Tree[A, B])(implicit val ordering:
     }
   }
 
+  override def keySet: SortedSet[A] = new DefaultKeySortedSet {
+    override def foreach[U](f: A => U): Unit = RB.foreachEntry(tree, {(key: A, _: B) => f(key)})
+  }
+
+  override def values: scala.Iterable[B] = new DefaultValuesIterable {
+    override def foreach[U](f: B => U): Unit = RB.foreachEntry(tree, {(_: A, value: B) => f(value)})
+  }
 }