how do I make analysis warnings trigger runtime failure

Question

In the following example, main is allowed to call a sniff function on Dog that I would prefer would somehow break. If I say exactly what a Dog can do, but somehow the client knows more and can get the object to do more with that special knowledge - I think that is an encapsulation leak. I don't necessarily want it to die in the general case, but is there a flag or way to run that would enforce that only methods be called if they exist. I know the language supports the knowledge that something is wrong since the Dart Editor displays a warning: The method 'sniff' is not defined for the class 'Dog'. Even when run with --checked flag, this runs fine.

So suppose similar code were invoked by a test. Is there a flag in Dart or some code to cause it to fail when the test is run?

abstract class Dog {
  void run();
  void bark();
}

class BigDog implements Dog {
  void run() => print("Big dog running");
  void bark() => print("Woof");
  void sniff() => print("Sniff");
}

main() {
  Dog bd = new BigDog();
  bd.run();
  bd.bark();
  bd.sniff();
}

Answer 1

You should ensure to run the tests in checked mode dart -c testfile.dart then type annotations are taken into account. You shouldn't use checked mode in production though because it slows down your application.

Answer 2

This isn't possible. The problem is that your instance really is a BigDog; and therefore it really has a sniff method. An important goal in Dart is that type annotations do not affect runtime behaviour; therefore your Dog annotation is unable to change the behaviour.

The tooling is able to highlight this because it does use the type annotations.

This sort of question comes up a lot in the Dart bug tracker; but it would be a pretty fundamental change to allow type annotations to change behaviour, so it's not something I expect would ever be considered; confusing as it might be. See here for some more info on this.