From 6d49dfd60664110f66801467755cdc7b06ccd09e Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Thu, 27 Feb 2020 11:26:36 +1000
Subject: [PATCH] temp

---
 .../scala/collection/immutable/HashMap.scala  | 56 ++++++++++---------
 .../scala/collection/mutable/HashMap.scala    |  8 ++-
 2 files changed, 38 insertions(+), 26 deletions(-)

diff --git a/src/library/scala/collection/immutable/HashMap.scala b/src/library/scala/collection/immutable/HashMap.scala
index d104f62a09f..88782263e93 100644
--- a/src/library/scala/collection/immutable/HashMap.scala
+++ b/src/library/scala/collection/immutable/HashMap.scala
@@ -22,6 +22,7 @@ import scala.collection.Stepper.EfficientSplit
 import scala.collection.generic.DefaultSerializable
 import scala.collection.mutable.ReusableBuilder
 import scala.collection.{Iterator, MapFactory, MapFactoryDefaults, Stepper, StepperShape, mutable}
+import scala.runtime.AbstractFunction2
 import scala.runtime.Statics.releaseFence
 import scala.util.hashing.MurmurHash3
 
@@ -184,35 +185,38 @@ final class HashMap[K, +V] private[immutable] (private[immutable] val rootNode:
       }
       this
     case _ =>
-      val iter = that.iterator
-      var current: BitmapIndexedMapNode[K, V1] = rootNode
-      while (iter.hasNext) {
-        val (key, value) = iter.next()
-        val originalHash = key.##
-        val improved = improve(originalHash)
-        current = current.updated(key, value, originalHash, improved, 0, replaceValue = true)
-
-        if (current ne rootNode) {
-          // Note: We could have started with shallowlyMutableNodeMap = 0, however this way, in the case that
-          // the first changed key ended up in a subnode beneath root, we mark that root right away as being
-          // shallowly mutable.
-          //
-          // since key->value has just been inserted, and certainly caused a new root node to be created, we can say with
-          // certainty that it either caused a new subnode to be created underneath `current`, in which case we should
-          // carry on mutating that subnode, or it ended up as a child data pair of the root, in which case, no harm is
-          // done by including its bit position in the shallowlyMutableNodeMap anyways.
-          var shallowlyMutableNodeMap = Node.bitposFrom(Node.maskFrom(improved, 0))
-
-          while (iter.hasNext) {
-            val (key, value) = iter.next()
-            val originalHash = key.##
-            val improved = improve(originalHash)
+      object accum extends AbstractFunction2[K, V1, Unit] with Function1[(K, V1), Unit] {
+        var changed = false
+        var shallowlyMutableNodeMap: Int = 0
+        var current: BitmapIndexedMapNode[K, V1] = rootNode
+        def apply(kv: (K, V1)) = apply(kv._1, kv._2)
+        def apply(key: K, value: V1): Unit = {
+          val originalHash = key.##
+          val improved = improve(originalHash)
+          if (!changed) {
+            current = current.updated(key, value, originalHash, improved, 0, replaceValue = true)
+            if (current ne rootNode) {
+              // Note: We could have started with shallowlyMutableNodeMap = 0, however this way, in the case that
+              // the first changed key ended up in a subnode beneath root, we mark that root right away as being
+              // shallowly mutable.
+              //
+              // since key->value has just been inserted, and certainly caused a new root node to be created, we can say with
+              // certainty that it either caused a new subnode to be created underneath `current`, in which case we should
+              // carry on mutating that subnode, or it ended up as a child data pair of the root, in which case, no harm is
+              // done by including its bit position in the shallowlyMutableNodeMap anyways.
+              changed = true
+              shallowlyMutableNodeMap = Node.bitposFrom(Node.maskFrom(improved, 0))
+            }
+          } else {
             shallowlyMutableNodeMap = current.updateWithShallowMutations(key, value, originalHash, improved, 0, shallowlyMutableNodeMap)
           }
-          return new HashMap(current)
         }
       }
-      this
+      that match {
+        case thatMap: Map[K, V1] => thatMap.foreachEntry(accum)
+        case _ => that.iterator.foreach(accum)
+      }
+      newHashMapOrThis(accum.current)
   }
 
   override def tail: HashMap[K, V] = this - head._1
@@ -2331,6 +2335,8 @@ private[immutable] final class HashMapBuilder[K, V] extends ReusableBuilder[(K,
           val hash = improve(originalHash)
           update(rootNode, next.key, next.value, originalHash, hash, 0)
         }
+      case thatMap: Map[K, V] =>
+        thatMap.foreachEntry((key, value) => addOne(key, value))
       case other =>
         val it = other.iterator
         while(it.hasNext) addOne(it.next())
diff --git a/src/library/scala/collection/mutable/HashMap.scala b/src/library/scala/collection/mutable/HashMap.scala
index fa07b836b1c..94e97402f9a 100644
--- a/src/library/scala/collection/mutable/HashMap.scala
+++ b/src/library/scala/collection/mutable/HashMap.scala
@@ -102,7 +102,13 @@ class HashMap[K, V](initialCapacity: Int, loadFactor: Double)
           put0(next.key, next.value, next.hash, getOld = false)
         }
         this
-      case _ => super.addAll(xs)
+      case thatMap: Map[K, V] =>
+        thatMap.foreachEntry { (key: K, value: V) =>
+          put0(key, value, key.##, getOld = false)
+        }
+        this
+      case _ =>
+        super.addAll(xs)
     }
   }