anchor.diff:          match t with
               | Struct(_,fields) ->
                   fields 
  -                |> List.mapi (fun i (t,n) -> (i,t,n))
  +                |> List.mapi (fun i (t,n,_) -> (i,t,n))
                   |> List.pick (fun (i,t,n) ->
                       if field = n then Some (i,t)
                       else None
  
positive.code:     | Vector of compType : Type * dim : int
      | Matrix of colType : Type * dim : int
      | Array of elementType : Type * length : int
      | Struct of name : string * fields : list<Type * string>
      | Image of sampledType : Type * dim : Dim * depth : int * arrayed : bool * ms : int * sampled : bool * format : int
      | SampledImage of Type
      | Ptr of StorageClass * Type
  
negative.code:         let m = new Var("m", myType, true)
  
  
          let ub0t = Struct("PerModel", [Type.M44f, "ModelViewProjTrafo", []])
          let ub0 = Var("perModel", ub0t, true)
  
          let ex = 
  