anchor.diff:    }  
       
     String toDebugString() => String$.debugString(e);
  +}
  +
  +class Num$ extends Mixin {
  +  num target;
  +  Num$(target) : super(target) {
  +    this.target = target;
  +  }
  +
  +  times(iterator(int n)) {
  +    for (int i = 0; i < e; i++) iterator(i);
  +  }    
   }
   
   class String$ extends Mixin {
  
positive.code:         (target) => target is Collection ? new List$(target) : null, 
          (target) => target is Map ? new Map$(target) : null,
          (target) => target is String ? new String$(target) : null,
          (target) => new Mixin(target),
        ];
      }
  
negative.code:     int id = _idCounter++;
      return prefix == null ? "$prefix$id" : id;
    }
    
    result(key) { 
      if (e == null) return null;
  