Mark the private[collection] HashTable as not used

src/library/scala/collection/mutable/HashTable.scala

@@ -35,8 +35,8 @@ import java.lang.Integer
  *
  *  @tparam A     type of the elements contained in this hash table.
  */
-// Was an abstract class, but to simplify the upgrade of the parallel collections I’ve made it a trait
-private[collection] /*abstract class*/ trait HashTable[A, B, Entry >: Null <: HashEntry[A, Entry]] extends HashTable.HashUtils[A] {
+// Not used in the standard library, but used in scala-parallel-collections
+private[collection] trait HashTable[A, B, Entry >: Null <: HashEntry[A, Entry]] extends HashTable.HashUtils[A] {
   // Replacing Entry type parameter by abstract type member here allows to not expose to public
   // implementation-specific entry classes such as `DefaultEntry` or `LinkedEntry`.
   // However, I'm afraid it's too late now for such breaking change.

src/library/scala/collection/mutable/OpenHashMap.scala

@@ -13,8 +13,8 @@
 package scala.collection
 package mutable
 
+import java.lang.Integer.numberOfLeadingZeros
 import java.util.ConcurrentModificationException
-
 import scala.collection.generic.DefaultSerializable
 
 /**
@@ -41,6 +41,8 @@ object OpenHashMap extends MapFactory[OpenHashMap] {
   final private class OpenEntry[Key, Value](var key: Key,
                                             var hash: Int,
                                             var value: Option[Value])
+
+  private[mutable] def nextPositivePowerOfTwo(target: Int): Int = 1 << -numberOfLeadingZeros(target - 1)
 }
 
 /** A mutable hash map based on an open addressing method. The precise scheme is
@@ -75,7 +77,7 @@ class OpenHashMap[Key, Value](initialSize : Int)
 
   override def mapFactory: MapFactory[OpenHashMap] = OpenHashMap
 
-  private[this] val actualInitialSize = HashTable.nextPositivePowerOfTwo(initialSize)
+  private[this] val actualInitialSize = OpenHashMap.nextPositivePowerOfTwo(initialSize)
 
   private[this] var mask = actualInitialSize - 1