Merge pull request scala/scala#10221 from liang3zy22/collectionbug12369

new LinkedHashMap/LinkedHashSet implementation

Author: lrytz

library/src/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.