Fix unzip issue

Author: Antoine Brunner

library/src-bootstrapped/scala/IArray.scala

@@ -191,10 +191,10 @@ object opaques
     def [T](arr: IArray[T]) takeWhile(p: T => Boolean): IArray[T] =
       arr.asInstanceOf[Array[T]].takeWhile(p).asInstanceOf
 
-    // def [T, U: ClassTag, V: ClassTag](arr: IArray[T]) unzip(given T => (U, V)): (IArray[U], IArray[V]) =
-    //   arr.asInstanceOf[Array[T]].unzip match {
-    //     case (x, y) => (x.asInstanceOf[IArray[U]], y.asInstanceOf[IArray[V]])
-    //   }
+    def [U: ClassTag, V: ClassTag](arr: IArray[(U, V)]) unzip: (IArray[U], IArray[V]) =
+      arr.asInstanceOf[Array[(U, V)]].unzip match {
+        case (x, y) => (x.asInstanceOf[IArray[U]], y.asInstanceOf[IArray[V]])
+      }
 
     def [T, U: ClassTag](arr: IArray[T]) zip(that: IterableOnce[U]): IArray[(T, U)] =
       arr.asInstanceOf[Array[T]].zip(that).asInstanceOf

tests/run-bootstrapped/iarray-extmtds.scala

@@ -1,5 +1,12 @@
 
 object Test extends App {
-  val arr = IArray[Int](1, 2, 3)
-  println(arr.take(2))
+  def assertNew[T, U](expr: => IArray[T], original: IArray[U]): Unit = {
+    val result = expr
+    assert(result ne original, "IArray was mutated in place")
+    println(result)
+  }
+
+  val arr = Array[Int](1,2,3,4,5,6,7,8,9,10)
+
+  assertNew(arr.filter(_ % 2 == 0), arr)
 }