[Feature request] Safe guard when iterate over properties.

[chunhtai]

I would like to have a better warning when writing method that needs to account for all properties.
For example when a class overrides operator== and hashCode of a class.

class A {
  int? a;
  int? b;

  void printAll() {
    if (a != null) {
      print(a);
    }
    if (b != null) {
      print(b);
    }
  }

  @override
  bool operator ==(Object other) {
    return other is A && other.a == a && other.b == b;
  }

    @override
  int get hashCode => Object.hashAll([a, b]);

}

it is very easy to forgot to update these method when adding new propperty which cause obscure bugs.

class A {
  int? a;
  int? b;
  int? c;

  void printAll() {
    if (a != null) {
      print(a);
    }
    if (b!= null) {
      print(b);
    }
    // may forgot to add
    if (c!= null) {
      print(c);
    }
  }

  @override
  bool operator ==(Object other) {
    return other is A && other.a == a && other.b == b
     // forgot 
     && other.c ==c ;
  }

    @override
  int get hashCode => Object.hashAll([a, b, /*forgot*/ c]);

}

I hope we could have a way to get warming about cases like this.

[FMorschel]

What are you proposing it would look for? All non-synthetic fields in a class? How do you want to tell the analyzer that the warning should trigger on printAll? Do you mean a new annotation?

[chunhtai]

I don't have concrete idea, but possible solution maybe a decorator or a properties enumeration syntax like

void printAll() {
  for(final Object property in $properties) {
    print(property);
  }
}

This is not type safe though.