Provide unzip method for Iterables, Arrays and Sequences of pairs.

#KT-5793 Fixed

libraries/stdlib/test/collections/CollectionTest.kt

@@ -621,6 +621,19 @@ class CollectionTest {
         assertEquals(e, 5)
     }
 
+    test fun unzipList() {
+        val list = listOf(1 to 'a', 2 to 'b', 3 to 'c')
+        val (ints, chars) = list.unzip()
+        assertEquals(listOf(1, 2, 3), ints)
+        assertEquals(listOf('a', 'b', 'c'), chars)
+    }
+
+    test fun unzipArray() {
+        val array = arrayOf(1 to 'a', 2 to 'b', 3 to 'c')
+        val (ints, chars) = array.unzip()
+        assertEquals(listOf(1, 2, 3), ints)
+        assertEquals(listOf('a', 'b', 'c'), chars)
+    }
 
     test fun specialLists() {
         compare(arrayListOf<Int>(), listOf<Int>()) { listBehavior() }

libraries/stdlib/test/collections/SequenceTest.kt

@@ -291,8 +291,7 @@ public class SequenceTest {
         assertEquals(listOf(0, 1, 3, 4), result.toList())
     }
 
-    test
-    fun flatten() {
+    test fun flatten() {
         val data = sequenceOf(1, 2).map { sequenceOf(0..it) }
         assertEquals(listOf(0, 1, 0, 1, 2), data.flatten().toList())
     }
@@ -307,6 +306,12 @@ public class SequenceTest {
         assertEquals(listOf(13, 34, 55, 144), sequence.distinctBy { it % 4 }.toList())
     }
 
+    test fun unzip() {
+        val seq = sequenceOf(1 to 'a', 2 to 'b', 3 to 'c')
+        val (ints, chars) = seq.unzip()
+        assertEquals(listOf(1, 2, 3), ints)
+        assertEquals(listOf('a', 'b', 'c'), chars)
+    }
 
     /*
     test fun pairIterator() {