Merge pull request scala/scala#7118 from joshlemer/mapbuilder-prototype

Optimize s.c.i.HashMap builder

Author: retronym

library/src/scala/collection/immutable/ChampCommon.scala

@@ -58,6 +58,15 @@ private[immutable] abstract class Node[T <: Node[T]] {
     result
   }
 
+  protected final def removeAnyElement(as: Array[Any], ix: Int): Array[Any] = {
+    if (ix < 0) throw new ArrayIndexOutOfBoundsException
+    if (ix > as.length - 1) throw new ArrayIndexOutOfBoundsException
+    val result = new Array[Any](as.length - 1)
+    arraycopy(as, 0, result, 0, ix)
+    arraycopy(as, ix + 1, result, ix, as.length - ix - 1)
+    result
+  }
+
   protected final def insertElement(as: Array[Int], ix: Int, elem: Int): Array[Int] = {
     if (ix < 0) throw new ArrayIndexOutOfBoundsException
     if (ix > as.length) throw new ArrayIndexOutOfBoundsException
@@ -67,6 +76,15 @@ private[immutable] abstract class Node[T <: Node[T]] {
     arraycopy(as, ix, result, ix + 1, as.length - ix)
     result
   }
+  protected final def insertAnyElement(as: Array[Any], ix: Int, elem: Int): Array[Any] = {
+    if (ix < 0) throw new ArrayIndexOutOfBoundsException
+    if (ix > as.length) throw new ArrayIndexOutOfBoundsException
+    val result = new Array[Any](as.length + 1)
+    arraycopy(as, 0, result, 0, ix)
+    result(ix) = elem
+    arraycopy(as, ix, result, ix + 1, as.length - ix)
+    result
+  }
 }
 
 /**