anchor.diff:  }
   
   class Room extends Card {
  -  const Room._(this.name);
  +  const Room._(name):super(name);
     
     static final Room HALL =
         const Room._("HALL");
  
positive.code: }
  
  class Weapon extends Card {
    const Weapon._(this.name);
    static final Weapon KNIFE =
        const Weapon._("KNIFE");
    static final Weapon CANDLESTICK =
  
negative.code: 
  abstract class Card {
    final String name;
    const Card(this.name);
  }
  
  class Character extends Card {
    const Character._(name):super(name);
    
    static final Character SCARLET =
        const Character._("SCARLET");
  