Sound Dart Guide: generic type assignment

main.dart

// Enable strong mode by clicking Strong mode checkbox in lower right.
// The code passes strong mode static analysis.
// Follow the instructions in the generic type assignment below.

class Animal {
  void feed() {}
}

class Alligator extends Animal {}

class Cat extends Animal {}

class MaineCoon extends Cat {}

void feedAnimals(Iterable<Animal> animals) {
  for (var animal in animals) {
    animal.feed();
  }
}

main(List<String> args) {
  List<Cat> myCats = new List<Cat>();  // Replace Cat with MaineCoon. It passes.
                                       // Replace with Animal. It passes.
                                       // Replace with Alligator. It fails.
  Cat muffin = new Cat();
  Cat winky = new Cat();
  Cat bongo = new Cat();
  myCats.addAll([muffin, winky, bongo]);

  feedAnimals(myCats);
}