Add mapIndexed() function for common case withIndex().map{} #KT-3153 Fixed

libraries/stdlib/test/collections/IterableTests.kt

@@ -15,7 +15,7 @@ class IterableWrapper<T>(collection: Iterable<T>) : Iterable<T> {
 }
 
 class IterableTest : IterableTests<Iterable<String>>(iterableOf("foo", "bar"), iterableOf<String>())
-class SetTest : IterableTests<Set<String>>(hashSetOf("foo", "bar"), hashSetOf<String>())
+class SetTest : IterableTests<Set<String>>(setOf("foo", "bar"), setOf<String>())
 class ListTest : OrderedIterableTests<List<String>>(listOf("foo", "bar"), listOf<String>())
 class ArrayListTest : OrderedIterableTests<ArrayList<String>>(arrayListOf("foo", "bar"), arrayListOf<String>())
 

libraries/stdlib/test/iterators/IteratorsTest.kt

@@ -30,6 +30,10 @@ class IteratorsTest {
         assertEquals(arrayListOf(0, 3, 3, 6, 9, 15), fibonacci().map { it * 3 }.takeWhile { (i: Int) -> i < 20 }.toList())
     }
 
+    test fun mapIndexed() {
+        assertEquals(arrayListOf(0, 1, 2, 6, 12), fibonacci().mapIndexed { index, value -> index * value }.takeWhile {(i: Int) -> i < 20 }.toList())
+    }
+
     test fun joinConcatenatesTheFirstNElementsAboveAThreshold() {
         assertEquals("13, 21, 34, 55, 89, ...", fibonacci().filter { it > 10 }.joinToString(separator = ", ", limit = 5))
     }