Sdk: package:meta: @mustCallSuper should not apply to 'implements'

[matanlurey]

Example case:

import 'package:meta/meta.dart';

/// An interface for a living breathing animal on Earth.
///
/// Animals are different sizes and may need to eat more or less.
abstract class Animal {
  /// Eat [food]. Throws exception if the animal is still hungry after eating.
  @mustCallSuper
  void eat(Food food) {
    if (isHungry) {
      throw 'Was not fed enough food!';
    }
  }

  bool get isHungry;
}

In this example, I'd assume that extends Animal triggers a warning I missed super.eat:

class TinyAnimal extends Animal {
  bool _isHungry = false;

  @override
  void eat(Food food) {
    _isHungry = false;
  }

  @override
  bool get isHungry => _isHungry;
}

However, this will _also_ (incorrectly) trigger a warning. I _can't_ call super:

class LargeAnimal implements Animal {
  bool _isHungry = false;

  @override
  void eat(Food food) {
    if (!food.isLargeAmount) {
      throw 'Large animals need large amounts of food!';
    }
    _isHungry = false;
  }

  @override
  bool get isHungry => _isHungry;
}

[bwilkerson]

Either that, or there should also be a hint if a class that has methods annotated with @mustCallSuper is implemented.

@Hixie Any thoughts?

[Hixie]

Yeah, this seems legit.

We should probably require that classes be annotate as @mixin or @interface to be used with "with" or "implements", which would address this somewhat, but that's another (already filed) bug.

[matanlurey]

In this specific case though I'd like Animal to be both implementable and extendable by default (Dart idioms that we see across the code base and I think are well respected). I could see the value of having @mixin (you _must_ mix me in) or @interface (you _must_ implement me), but I think those are somewhat separate.

[Hixie]

Oh yeah I'm not saying this would be required. A package would have to opt-in to this kind of thing for sure.

[bwilkerson]

https://codereview.chromium.org/2348383006/

[matanlurey]

Thanks Brian!