type 'a conv = [ | `Result of 'a| `Error of exn * t
]exception Conv_exn of string * exntype stack = {mutable positions : pos list;mutable stack : t list list;
}val sexp_of_conv :
('a -> Type.t) ->
[< `Error of exn * t | `Result of 'b ] ->
Type.texception Annot_sexp of t