fixes #202, check IndexExpression

tool/sdk_expected_errors.txt

 warning: line 20, column 39 of dart:async/async_error.dart: [DownCastImplicit] errorHandler (Function) will need runtime check to cast to type (dynamic) → dynamic
     return zone.registerUnaryCallback(errorHandler);
                                       ^^^^^^^^^^^^
 severe: line 211, column 38 of dart:async/broadcast_stream_controller.dart: [AnalyzerError] The getter '_next' is not defined for the class 'StreamSubscription<T>'
       assert(!identical(subscription._next, subscription));
                                      ^^^^^
 severe: line 207, column 36 of dart:async/broadcast_stream_controller.dart: [AnalyzerError] The getter '_next' is not defined for the class 'StreamSubscription<T>'
     assert(!identical(subscription._next, subscription));
                                    ^^^^^
 severe: line 209, column 20 of dart:async/broadcast_stream_controller.dart: [AnalyzerError] The method '_setRemoveAfterFiring' is not defined for the class 'StreamSubscription<T>'
@@ skipping 685 matching lines @@
                                               ^^^^
 warning: line 997, column 40 of dart:_internal/iterable.dart: [DownCastComposite] list (List<dynamic>) will need runtime check to cast to type Iterable<T>
     return new ReversedListIterable<T>(list);
                                        ^^^^
 warning: line 1033, column 35 of dart:_internal/iterable.dart: [DownCastComposite] list (List<dynamic>) will need runtime check to cast to type Iterable<T>
     return new SubListIterable<T>(list, start, end);
                                   ^^^^
 warning: line 1115, column 31 of dart:_internal/iterable.dart: [DownCastComposite] l (List<dynamic>) will need runtime check to cast to type List<T>
     return new ListMapView<T>(l);
                               ^
+warning: line 251, column 59 of dart:_internal/list.dart: [DownCastImplicit] key (Object) will need runtime check to cast to type int
+  E operator[] (Object key) => containsKey(key) ? _values[key] : null;
+                                                          ^^^
 warning: line 179, column 12 of dart:collection: [DownCastComposite] JS('var', '#.splice(#, 2)[1]', bucket, index) (dynamic) will need runtime check to cast to type V
     return JS('var', '#.splice(#, 2)[1]', bucket, index);
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 warning: line 193, column 14 of dart:collection: [DownCastComposite] key (dynamic) will need runtime check to cast to type K
       action(key, this[key]);
              ^^^
 warning: line 261, column 17 of dart:collection: [DownCastComposite] _getTableEntry(table, key) (dynamic) will need runtime check to cast to type V
       V value = _getTableEntry(table, key);
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 severe: line 372, column 61 of dart:collection: [InvalidRuntimeCheckError] Invalid runtime check on non-ground type K
@@ skipping 97 matching lines @@
                                    ^^^^^^^
 warning: line 1616, column 47 of dart:collection: [DownCastComposite] element (dynamic) will need runtime check to cast to type E
     return JS('int', '# & 0x3ffffff', _hasher(element));
                                               ^^^^^^^
 warning: line 1678, column 18 of dart:collection: [DownCastComposite] _cell._element (dynamic) will need runtime check to cast to type E
       _current = _cell._element;
                  ^^^^^^^^^^^^^^
 warning: line 112, column 40 of dart:collection/hash_map.dart: [DownCastComposite] v (dynamic) will need runtime check to cast to type V
     other.forEach((k, v) { result[k] = v; });
                                        ^
+warning: line 112, column 35 of dart:collection/hash_map.dart: [DownCastComposite] k (dynamic) will need runtime check to cast to type K
+    other.forEach((k, v) { result[k] = v; });
+                                  ^
 warning: line 128, column 17 of dart:collection/hash_set.dart: [DownCastComposite] elements (Iterable<dynamic>) will need runtime check to cast to type Iterable<E>
     for (E e in elements) result.add(e);
                 ^^^^^^^^
 warning: line 33, column 16 of dart:collection/iterator.dart: [DownCastComposite] _iterator.current (dynamic) will need runtime check to cast to type E
     E result = _iterator.current;
                ^^^^^^^^^^^^^^^^^
 warning: line 99, column 40 of dart:collection/linked_hash_map.dart: [DownCastComposite] v (dynamic) will need runtime check to cast to type V
     other.forEach((k, v) { result[k] = v; });
                                        ^
+warning: line 99, column 35 of dart:collection/linked_hash_map.dart: [DownCastComposite] k (dynamic) will need runtime check to cast to type K
+    other.forEach((k, v) { result[k] = v; });
+                                  ^
 warning: line 142, column 12 of dart:collection/linked_hash_map.dart: [DownCastComposite] fillLiteralMap(keyValuePairs, new _LinkedHashMap<K, V>()) (dynamic) will need runtime check to cast to type LinkedHashMap<K, V>
     return fillLiteralMap(keyValuePairs, new _LinkedHashMap<K, V>());
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 warning: line 65, column 56 of dart:collection/linked_list.dart: [DownCastComposite] entry (dynamic) will need runtime check to cast to type E
     entries.forEach((entry) => _insertAfter(_previous, entry));
                                                        ^^^^^
 warning: line 93, column 17 of dart:collection/linked_list.dart: [DownCastComposite] next (_LinkedListLink) will need runtime check to cast to type E
       E entry = next;
                 ^^^^
 warning: line 105, column 12 of dart:collection/linked_list.dart: [DownCastComposite] _next (_LinkedListLink) will need runtime check to cast to type E
@@ skipping 76 matching lines @@
            ^^^^^^^
 warning: line 265, column 23 of dart:collection/splay_tree.dart: [DownCastComposite] (compare == null) ? Comparable.compare : compare (dynamic) will need runtime check to cast to type (K, K) → int
       : _comparator = (compare == null) ? Comparable.compare : compare,
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 severe: line 266, column 65 of dart:collection/splay_tree.dart: [InvalidRuntimeCheckError] Invalid runtime check on non-ground type K
         _validKey = (isValidKey != null) ? isValidKey : ((v) => v is K);
                                                                 ^^^^^^
 warning: line 275, column 40 of dart:collection/splay_tree.dart: [DownCastComposite] v (dynamic) will need runtime check to cast to type V
     other.forEach((k, v) { result[k] = v; });
                                        ^
+warning: line 275, column 35 of dart:collection/splay_tree.dart: [DownCastComposite] k (dynamic) will need runtime check to cast to type K
+    other.forEach((k, v) { result[k] = v; });
+                                  ^
 warning: line 328, column 25 of dart:collection/splay_tree.dart: [DownCastComposite] key (Object) will need runtime check to cast to type K
       int comp = _splay(key);
                         ^^^
 warning: line 331, column 16 of dart:collection/splay_tree.dart: [DownCastComposite] mapRoot.value (dynamic) will need runtime check to cast to type V
         return mapRoot.value;
                ^^^^^^^^^^^^^
 warning: line 339, column 41 of dart:collection/splay_tree.dart: [DownCastComposite] key (Object) will need runtime check to cast to type K
     _SplayTreeMapNode mapRoot = _remove(key);
                                         ^^^
 warning: line 340, column 33 of dart:collection/splay_tree.dart: [DownCastComposite] mapRoot.value (dynamic) will need runtime check to cast to type V
@@ skipping 250 matching lines @@
                       ^^^^^^^^^^^^^^^^
 warning: line 1869, column 12 of dart:core/uri.dart: [DownCastComposite] query.split("&").fold({}, (map, element) {int index = element.indexOf("="); if (index == -1) {if (element != "") {map[decodeQueryComponent(element, encoding: encoding)] = "";}} else if (index != 0) {var key = element.substring(0, index); var value = element.substring(index + 1); map[Uri.decodeQueryComponent(key, encoding: encoding)] = decodeQueryComponent(value, encoding: encoding);} return map;}) (dynamic) will need runtime check to cast to type Map<String, String>
     return query.split("&").fold({}, (map, element) {
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 warning: line 1901, column 12 of dart:core/uri.dart: [DownCastComposite] bytes.map((byteString) {int byte = int.parse(byteString); if (byte < 0 || byte > 255) {error('each part must be in the range of `0..255`');} return byte;}).toList() (List<dynamic>) will need runtime check to cast to type List<int>
     return bytes
            ^^^^^^
 warning: line 2023, column 12 of dart:core/uri.dart: [DownCastComposite] bytes (List<dynamic>) will need runtime check to cast to type List<int>
     return bytes;
            ^^^^^