class A {}

class B<X> {
  B() : this._(0, '');
  B._(this.field1, this.field2);
  B.foo(this.field1) : field2 = '';
  String field2;
  factory B.bar(int i, String j) => new B<X>._(i, j);
  int field1;
}

expect(expected, actual) {}
final bool inSoundMode = <int?>[] is! List<int>;
main() {}
throws(Function() f, {bool inSoundModeOnly: false}) {}
typedef DA1 = A;
typedef DA2<X extends num> = A;
typedef DB1 = B<String>;
typedef DB2<X extends num> = B<X>;
typedef DB3<X extends num, Y extends String> = B<X>;