class A {
  A get nonNullableProperty => this;
  const A();
}

class Class {
  A get nonNullableProperty => nonNullableField;
  A nonNullableField = const A();
  A nonNullableMethod() => nonNullableField;
  void set nonNullableProperty(A value) {}
}

expect(expected, actual) {}
main() {}
throws(void Function() f) {}