adapt to scala/scala#7929

Author: adriaanm

build.sbt

@@ -5,7 +5,7 @@ version in ThisBuild := "0.1.3-SNAPSHOT"
 resolvers in ThisBuild += "scala-integration" at "https://scala-ci.typesafe.com/artifactory/scala-integration/"
 
 scalaVersionsByJvm in ThisBuild := {
-  val v213 = "2.13.0-pre-59975bb"  // Mar 28
+  val v213 = "2.13.0-pre-041fc23"  // Apr 2
   Map(
     8 -> List(v213 -> true),
     11 -> List(v213 -> false),

core/src/main/scala/scala/collection/immutable/OldHashMap.scala

@@ -31,6 +31,7 @@ sealed abstract class OldHashMap[K, +V]
     with MapOps[K, V, OldHashMap, OldHashMap[K, V]]
     with StrictOptimizedIterableOps[(K, V), Iterable, OldHashMap[K, V]]
     with StrictOptimizedMapOps[K, V, OldHashMap, OldHashMap[K, V]]
+    with collection.MapFactoryDefaults[K, V, OldHashMap, Iterable]
     with Serializable {
 
   import OldHashMap.{bufferSize, liftMerger, Merger, MergeFunction, nullToEmpty}

core/src/main/scala/scala/collection/immutable/OldHashSet.scala

@@ -27,6 +27,7 @@ sealed abstract class OldHashSet[A]
   extends AbstractSet[A]
     with SetOps[A, OldHashSet, OldHashSet[A]]
     with StrictOptimizedIterableOps[A, OldHashSet, OldHashSet[A]]
+    with collection.IterableFactoryDefaults[A, OldHashSet]
     with Serializable {
 
   import OldHashSet.{bufferSize, LeafOldHashSet, nullToEmpty}