Yep I meant that there should be a leading `_`

```dart
main() {
  final list = <int>[1, 2, 3];

  list.add('a');

  print(list);
}
```

executed in `--checked` mode

```
Unhandled exception:
type 'String' is not a subtype of type 'int' of 'value'.
#0      List.add (dart:core-patch/growable_array.dart:176)
#1      main (file:///var/www/localhost/sites/dart-test/lib/hi/hi.dart:12:11)
#2      _startIsolate.isolateStartHandler (dart:isolate-patch/isolate_patch.dart:216)
#3      _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:115)
```