anchor.diff:          match source with
           | :? Symbol as symbol ->
               match symbol with
  -            | Symbols ([Number (x, _); Number (y, _); Number (z, _); Number (w, _)], _) ->
  -                Box2i (scvalue x, scvalue y, scvalue z, scvalue w) :> obj
  +            | Symbols ([positionSymbol; sizeSymbol], _) ->
  +                match (positionSymbol, sizeSymbol) with
  +                | (Symbols ([Number (px, _); Number (py, _)], _), Symbols ([Number (sx, _); Number (sy, _)], _)) ->
  +                    Box2i (scvalue px, scvalue py, scvalue sx, scvalue sy) :> obj
  +                | _ ->
  +                    failconv "Invalid Box2iConverter conversion from source." (Some symbol)
               | _ ->
                   failconv "Invalid Box2iConverter conversion from source." (Some symbol)
  -        | :? Box2i -> source
  +        | :? Box2 -> source
           | _ -> failconv "Invalid Box2iConverter conversion from source." None
   
   [<AutoOpen>]
  
positive.code:         if destType = typeof<Symbol> then
              let box2 = source :?> Box2
              Symbols
                  ([Number (scstring box2.Position.X, None)
                    Number (scstring box2.Position.Y, None)
                    Number (scstring box2.Size.X, None)
                    Number (scstring box2.Size.Y, None)], None) :> obj
          elif destType = typeof<Box2> then source
          else failconv "Invalid Box2Converter conversion to source." None
  
  
negative.code: 
      override this.ConvertTo (_, _, source, destType) =
          if destType = typeof<Symbol> then
              let box2i = source :?> Box2i
              Symbols
                  ([Symbols ([Number (scstring box2i.Position.X, None); Number (scstring box2i.Position.Y, None)], None)
                    Symbols ([Number (scstring box2i.Size.X, None); Number (scstring box2i.Size.Y, None)], None)], None) :> obj
          elif destType = typeof<Box2i> then source
          else failconv "Invalid Box2iConverter conversion to source." None
  
  