fix #214, check type of inferred initializing formal with default value

tool/sdk_expected_errors.txt

 warning: line 80, column 12 of dart:_interceptors/js_array.dart: [DownCastComposite] JS('var', r'#.pop()', this) (dynamic) will need runtime check to cast to type E
     return JS('var', r'#.pop()', this);
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 warning: line 125, column 9 of dart:_interceptors/js_array.dart: [DownCastComposite] JS('', '#[#]', this, i) (dynamic) will need runtime check to cast to type E
       f(JS('', '#[#]', this, i));
         ^^^^^^^^^^^^^^^^^^^^^^^
 warning: line 161, column 12 of dart:_interceptors/js_array.dart: [DownCastComposite] IterableMixinWorkaround.reduce(this, combine) (dynamic) will need runtime check to cast to type E
     return IterableMixinWorkaround.reduce(this, combine);
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 warning: line 169, column 12 of dart:_interceptors/js_array.dart: [DownCastComposite] IterableMixinWorkaround.firstWhere(this, test, orElse) (dynamic) will need runtime check to cast to type E
@@ skipping 241 matching lines @@
                                       ^^^^^^^^
 warning: line 378, column 17 of dart:_internal/iterable.dart: [DownCastComposite] iterable (Iterable<dynamic>) will need runtime check to cast to type Iterable<S>
       : super._(iterable, function);
                 ^^^^^^^^
 warning: line 454, column 76 of dart:_internal/iterable.dart: [DownCastComposite] _f ((dynamic) → Iterable<dynamic>) will need runtime check to cast to type (S) → Iterable<T>
   Iterator<T> get iterator => new ExpandIterator<S, T>(_iterable.iterator, _f);
                                                                            ^^
 warning: line 481, column 29 of dart:_internal/iterable.dart: [DownCastComposite] _f(_iterator.current).iterator (Iterator<dynamic>) will need runtime check to cast to type Iterator<T>
         _currentExpansion = _f(_iterator.current).iterator;
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-warning: line 555, column 57 of dart:_internal/iterable.dart: [DownCastComposite] _f ((dynamic) → bool) will need runtime check to cast to type (E) → bool
-    return new TakeWhileIterator<E>(_iterable.iterator, _f);
-                                                        ^^
-warning: line 648, column 57 of dart:_internal/iterable.dart: [DownCastComposite] _f ((dynamic) → bool) will need runtime check to cast to type (E) → bool
-    return new SkipWhileIterator<E>(_iterable.iterator, _f);
-                                                        ^^
 warning: line 961, column 33 of dart:_internal/iterable.dart: [DownCastComposite] iterable (Iterable<dynamic>) will need runtime check to cast to type Iterable<T>
     return new WhereIterable<T>(iterable, f);
                                 ^^^^^^^^
 warning: line 961, column 43 of dart:_internal/iterable.dart: [DownCastComposite] f ((dynamic) → bool) will need runtime check to cast to type (T) → bool
     return new WhereIterable<T>(iterable, f);
                                           ^
 warning: line 978, 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, 0, n);
                                   ^^^^
 warning: line 983, column 37 of dart:_internal/iterable.dart: [DownCastComposite] iterable (Iterable<dynamic>) will need runtime check to cast to type Iterable<T>
@@ skipping 796 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;
            ^^^^^