How can I fix the MissingFieldException Error

So I've been trying to make a puzzle game for one of my old teachers. I've been working on a script but whenever I use it it gives me this error:

MissingFieldException: System.Single.transform Boo.Lang.Runtime.DynamicDispatching.PropertyDispatcherFactory.FindExtension (IEnumerable`1 candidates) Boo.Lang.Runtime.DynamicDispatching.PropertyDispatcherFactory.Create (SetOrGet gos) Boo.Lang.Runtime.DynamicDispatching.PropertyDispatcherFactory.CreateGetter () Boo.Lang.Runtime.RuntimeServices.DoCreatePropGetDispatcher (System.Object target, System.Type type, System.String name) Boo.Lang.Runtime.RuntimeServices.CreatePropGetDispatcher (System.Object target, System.String name) Boo.Lang.Runtime.RuntimeServices+c_AnonStorey17.<>m_C () Boo.Lang.Runtime.DynamicDispatching.DispatcherCache.Get (Boo.Lang.Runtime.DynamicDispatching.DispatcherKey key, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory) Boo.Lang.Runtime.RuntimeServices.GetDispatcher (System.Object target, System.String cacheKeyName, System.Type[] cacheKeyTypes, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory) Boo.Lang.Runtime.RuntimeServices.GetDispatcher (System.Object target, System.Object[] args, System.String cacheKeyName, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory) Boo.Lang.Runtime.RuntimeServices.GetProperty (System.Object target, System.String name) UnityScript.Lang.UnityRuntimeServices.GetProperty (System.Object target, System.String name) UnityEngine.SendMouseEvents:DoSendMouseEvents(Int32, Int32)

Here's the Script:

 var Empty : Transform;
 var PosY;
 var PosX;
 
 function OnMouseUp(){                    
         if (Vector3.Distance(transform.position,Empty.position)==1){
         PosY = transform.position.x;
         PosX = transform.position.y;
         PosY.transform.position = Empty.position.y;
         PosX.transform.position = Empty.position.x;
         Empty.position = PosX;
         Empty.position = PosY;
         }
     
     
     
     
     
     
     //empty ray
     var hit : RaycastHit;
     
     //spawn said ray at mouse position
     var ray : Ray = Camera.main.ScreenPointToRay(Input.mousePosition);
 
     if(Physics.Raycast(ray,hit)){
         //Print out the objects name in Console
         Debug.Log(hit.collider.name);
     }    
 }

If you could tell me whats wrong and how I could fix it that'd be great. I've already tried looking around and unless I'm blind I cant find anything on this. Again any help would be appreciated.