type ideas in dart

ideas.dart

/// Extensible enum that has `instance.asKnown` for good switch tooling
enum KnownReleaseType {
  ALPHA,
  BETA,
  GAMMA,
}

class ReleaseType {
  ReleaseType(String value) : value = _parseValue(value);

  final Object value;

  static const ALPHA = KnownReleaseType.ALPHA;
  static const BETA = KnownReleaseType.BETA;
  static const GAMMA = KnownReleaseType.GAMMA;

  KnownReleaseType get asKnown => value is KnownReleaseType ? value : null;

  static Object _parseValue(String value) {
    switch (value) {
      case 'ALPHA':
        return KnownReleaseType.ALPHA;
      case 'BETA':
        return KnownReleaseType.BETA;
      case 'GAMMA':
        return KnownReleaseType.GAMMA;
    }
    return value;
  }

  @override
  int get hashCode => value.hashCode;
  @override
  bool operator ==(Object o) => o is ReleaseType && o.value == value;
}

I bet enum + extension can be hacked into variants

enum E { foo, biz, bar }

extension F on E {
  E shift(){
    switch(this){
      case E.foo:
        return E.biz;
       case E.biz:
        return E.bar;
      case E.bar:
        return E.foo;
     }
    throw Error();
  }
}


void main() {
  print(E.foo.shift().shift());
}