Hi,

> You program below is exactly equivalent to the following,
> without as. Or is your real code something different?

You're right, the formulation without 'as' is simpler, and Sexplib handles
it just fine.  The real code adds a phantom type variable to t, and the
advantage of using 'as' was making the phantomness obvious:

type +'a t = private [< 'b node_t ] as 'b

versus

type +'a t = private [< 'a t node_t ]

But in this case, 'as' does raise more trouble than it's worth...
Anyway, issue solved -- thanks!

Best regards,
Dario Teixeira