fixes #202, check IndexExpression

test/dart_codegen/expect/collection/splay_tree.dart

 part of dart.collection;
  typedef bool _Predicate<T>(T value);
  class _SplayTreeNode<K> {final K key;
  _SplayTreeNode<K> left;
  _SplayTreeNode<K> right;
  _SplayTreeNode(K this.key);
 }
  class _SplayTreeMapNode<K, V> extends _SplayTreeNode<K> {V value;
  _SplayTreeMapNode(K key, V this.value) : super(key);
 }
@@ skipping 133 matching lines @@
 }
 }
  class SplayTreeMap<K, V> extends _SplayTree<K> implements Map<K, V> {Comparator<K> _comparator;
  _Predicate<Object> _validKey;
  SplayTreeMap([int compare(K key1, K key2), bool isValidKey(Object potentialKey)]) : _comparator = ((__x12) => DEVC$RT.cast(__x12, dynamic, DEVC$RT.type((Comparator<K> _) {
 }
 ), "CompositeCast", """line 265, column 23 of dart:collection/splay_tree.dart: """, __x12 is Comparator<K>, false))((compare == null) ? Comparable.compare : compare), _validKey = (isValidKey != null) ? isValidKey : ((v) => v is K);
  factory SplayTreeMap.from(Map other, [int compare(K key1, K key2), bool isValidKey(Object potentialKey)]) {
 SplayTreeMap<K, V> result = new SplayTreeMap<K, V>();
  other.forEach((k, v) {
-result[k] = DEVC$RT.cast(v, dynamic, V, "CompositeCast", """line 275, column 40 of dart:collection/splay_tree.dart: """, v is V, false);
+result[DEVC$RT.cast(k, dynamic, K, "CompositeCast", """line 275, column 35 of dart:collection/splay_tree.dart: """, k is K, false)] = DEVC$RT.cast(v, dynamic, V, "CompositeCast", """line 275, column 40 of dart:collection/splay_tree.dart: """, v is V, false);
 }
 );
  return result;
 }
  factory SplayTreeMap.fromIterable(Iterable iterable, {
 K key(element), V value(element), int compare(K key1, K key2), bool isValidKey(Object potentialKey)}
 ) {
 SplayTreeMap<K, V> map = new SplayTreeMap<K, V>(compare, isValidKey);
  Maps._fillMapWithMappedIterable(map, iterable, key, value);
  return map;
@@ skipping 366 matching lines @@
  return new _SplayTreeNode<E>(node.key)..left = _copyNode(node.left)..right = _copyNode(node.right);
 }
  void clear() {
 _clear();
 }
  Set<E> toSet() => _clone();
  String toString() => IterableBase.iterableToFullString(this, '{', '}');
 }
  typedef int __CastType14<K>(K __u15, K __u16);
  typedef bool __CastType17(Object __u18);