structure M = struct
datatype t = A | B
end
val f = fn x : M.t => case x of M.A => M.B | M.B => M.A
datatype t = datatype M.t
val g = fn x : t => case x of M.A => B | B => M.A
structure N = struct
datatype u = C of t | D
end
val h = fn x : N.u => case x of N.C x => x | N.D => M.A
datatype u = datatype N.u
val i = fn x : u => case x of N.C x => x | D => M.A
val toString = fn x =>
case x of
C A => "C A"
| C B => "C B"
| D => "D"
val rec page = fn x =>
{cdata (toString x)}

Again!
val main : unit -> page = fn () =>
C A
C B
D