See this code:

void main() async {
  await Future<int>.error('error').catchError((e) {});
}

This code is guaranteed to throw a runtime error. However, there is currently no static error reported. As part of dart-lang/sdk#49215, the dart analyzer will start to report static errors for code like this. Before analyzer can start reporting these static errors by default, the Flutter codebases must be cleaned of them.