Allow for-in to use a previously declared identifier as variable.

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);
+
+  i = 0;
+  var value2;
+  for (value2 in input) {
+    Expect.isTrue(i < expect.length);
+    Expect.equals(expect[i], value2);
+    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"]));
+
+  // Several nested for-in's.
+  for (var x in [[["a"]]]) {
+    for (var y in x) {
+      for (var z in y) {
+        Expect.equals("a", z);
+      }
+    }
+  }
+
+  // Simultaneous iteration of the same iterable.
+  for (var iterable in [[1,2,3], new MyIterable([1,2,3])]) {
+    int result = 0;
+    for (var x in iterable) {
+      for (var y in iterable) {
+        result += x * y;
+      }
+    }
+    Expect.equals(36, result);
+  }
+
+  // Using the same variable (showing that the expression is evaluated
+  // in the outer scope).
+  int result = 0;
+  var x = [1,2,3];
+  for (var x in x) {
+    result += x;
+  }
+  Expect.equals(6, result);
 }