Re: higher-order functors

I managed to pare my code down to as simple an example I could that 
generates the compiler error (see below).

Thanks,
Dave

----------

signature COROUTINE =
sig
     type result
     type C

     val new : ((C * result) -> result) -> C
end;

funsig MK_COROUTINE (type result) = COROUTINE where type result = result;

functor MyCoroutine (type result) : COROUTINE =
struct
     type result = result

     datatype COROUTINE = Co

     type C = COROUTINE

     fun new f = Co
end

signature GENERATOR =
sig
     type G

     val make  : (G -> unit) -> G
end

functor Generator(functor MkCoroutine : MK_COROUTINE) : GENERATOR =
struct
     datatype signal = S

     structure Coroutine : COROUTINE =
         MkCoroutine (type result = signal)

     datatype G = Generator of Coroutine.C

     fun make f =
         Generator (Coroutine.new (fn _ => S))
end

structure G = Generator(functor MkCoroutine = MyCoroutine)


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