anchor.diff:  type AdaptiveDecorator(o : IAdaptiveObject) =
       let mutable o = o
       let id = newId()
  -    
  +    let mutable weakThis = null
  +
       member x.Id = id
       member x.OutOfDate
           with get() = o.OutOfDate
  
positive.code: 
  
      abstract member InputChanged : IAdaptiveObject -> unit
      
  
  /// <summary>
  /// LevelChangedException is internally used by the system
  
negative.code:                 x.Mark ()
  
              member x.InputChanged ip = x.InputChanged ip
              
      end
  
  
  