Fix progression iterators to respect the Iterator contract.

#KT-16923 Fixed

core/builtins/src/kotlin/ProgressionIterators.kt

@@ -23,15 +23,16 @@ package kotlin.ranges
  * @property step the number by which the value is incremented on each step.
  */
 internal class CharProgressionIterator(first: Char, last: Char, val step: Int) : CharIterator() {
-    private var next = first.toInt()
     private val finalElement = last.toInt()
     private var hasNext: Boolean = if (step > 0) first <= last else first >= last
+    private var next = if (hasNext) first.toInt() else finalElement
 
     override fun hasNext(): Boolean = hasNext
 
     override fun nextChar(): Char {
         val value = next
         if (value == finalElement) {
+            if (!hasNext) throw kotlin.NoSuchElementException()
             hasNext = false
         }
         else {
@@ -46,15 +47,16 @@ internal class CharProgressionIterator(first: Char, last: Char, val step: Int) :
  * @property step the number by which the value is incremented on each step.
  */
 internal class IntProgressionIterator(first: Int, last: Int, val step: Int) : IntIterator() {
-    private var next = first
     private val finalElement = last
     private var hasNext: Boolean = if (step > 0) first <= last else first >= last
+    private var next = if (hasNext) first else finalElement
 
     override fun hasNext(): Boolean = hasNext
 
     override fun nextInt(): Int {
         val value = next
         if (value == finalElement) {
+            if (!hasNext) throw kotlin.NoSuchElementException()
             hasNext = false
         }
         else {
@@ -69,15 +71,16 @@ internal class IntProgressionIterator(first: Int, last: Int, val step: Int) : In
  * @property step the number by which the value is incremented on each step.
  */
 internal class LongProgressionIterator(first: Long, last: Long, val step: Long) : LongIterator() {
-    private var next = first
     private val finalElement = last
     private var hasNext: Boolean = if (step > 0) first <= last else first >= last
+    private var next = if (hasNext) first else finalElement
 
     override fun hasNext(): Boolean = hasNext
 
     override fun nextLong(): Long {
         val value = next
         if (value == finalElement) {
+            if (!hasNext) throw kotlin.NoSuchElementException()
             hasNext = false
         }
         else {

generators/src/org/jetbrains/kotlin/generators/builtins/progressionIterators.kt

@@ -36,15 +36,16 @@ fun integerProgressionIterator(kind: ProgressionKind): String {
  * @property step the number by which the value is incremented on each step.
  */
 internal class ${t}ProgressionIterator(first: $t, last: $t, val step: $incrementType) : ${t}Iterator() {
-    private var next = first$toInt
     private val finalElement = last$toInt
     private var hasNext: Boolean = if (step > 0) first <= last else first >= last
+    private var next = if (hasNext) first$toInt else finalElement
 
     override fun hasNext(): Boolean = hasNext
 
     override fun next$t(): $t {
         val value = next
         if (value == finalElement) {
+            if (!hasNext) throw kotlin.NoSuchElementException()
             hasNext = false
         }
         else {

libraries/stdlib/test/ranges/RangeIterationTest.kt

@@ -1,6 +1,8 @@
 package test.ranges
 
 import org.junit.Test
+import test.collections.behaviors.iteratorBehavior
+import test.collections.compare
 import kotlin.test.*
 
 public open class RangeIterationTestBase {
@@ -41,6 +43,10 @@ public open class RangeIterationTestBase {
             assertTrue(sequence.none())
         else
             assertEquals(expectedElements, sequence.toList())
+
+        compare(expectedElements.iterator(), sequence.iterator()) {
+            iteratorBehavior()
+        }
     }
 
 }