Implement for-in.

frog/tests/leg_only/src/ForInTest.dart

+// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Test foreach (aka. for-in) functionality.
+
+testIterator(List expect, Iterable input) {
+  int i = 0;
+  for (var value in input) {
+    Expect.isTrue(i < expect.length);
+    Expect.equals(expect[i], value);
+    i += 1;
+  }
+  Expect.equals(expect.length, i);
+}
+
+class MyIterable<T> /* implements Iterable<T> */ {
+  final List<T> values;
+  MyIterable(List<T> values) : this.values = values;
+  Iterator iterator() {
+    return new MyListIterator(values);
+  }
+}
+
+class MyListIterator<T> /* implements Iterator<T> */ {
+  final List<T> values;
+  int index;
+  MyListIterator(List<T> values) : this.values = values, index = 0;
+  bool hasNext() => index < values.length;
+  T next() => values[index++];
+}
+
+void main() {
+  testIterator([], []);
+  testIterator([], new MyIterable([]));
+  testIterator([1], [1]);
+  testIterator([1], new MyIterable([1]));
+  testIterator([1,2,3], [1,2,3]);
+  testIterator([1,2,3], new MyIterable([1,2,3]));
+  testIterator(["a","b","c"], ["a","b","c"]);
+  testIterator(["a","b","c"], new MyIterable(["a","b","c"]));
+}