mkWpFun :: HsWrapper -> HsWrapper -> TcType -> TcType -> HsWrapper
mkWpFun WpHole       WpHole       _  _  = WpHole
mkWpFun :: HsWrapper -> HsWrapper -> TcType -> TcType -> HsWrapper
mkWpFun WpHole       WpHole       _  _  = WpHole
mkWpFun WpHole       WpHole       _  _  = WpHole