signature S = sig
        type t
        val x : t
end

structure M : S = struct
        val x = 0
end

signature S = sig
        con r :: {Type}
        val x : $r
end

structure M : S = struct
        val x = {A = 0, B = "Hi"}
end

signature S = sig
        type t
        con r :: {Type}
        val x : t -> $r
end

structure M : S = struct
        val x = fn v : int => {A = 0, B = "Hi"}
end