class gui = fn (t :: Type) (ctx :: {Unit}) => [body ~ ctx] => t -> xml (body ++ ctx) [] []

fun gui_xbody [body ~ []] x = x
fun gui_xtable [body ~ _] x = x

fun mkGui [t ::: Type] [ctx ::: {Unit}] (toXml : [body ~ ctx] => t -> xml (body ++ ctx) [] []) = @toXml

fun toXml [t ::: Type] [ctx ::: {Unit}] [body ~ ctx] (toXml : gui t ctx) = toXml