Dead links to hidden items appearing in documentation

[lpw25]

In the Field module in base we have the following code:

(**/**)
module For_generated_code : sig
  (*_ don't use this by hand, it is only meant for ppx_fields_conv *)

  type ('perm, 'record, 'field) t =
    { force_variance : 'perm -> unit
    ; name : string
    ; setter : ('record -> 'field -> unit) option
    ; getter : 'record -> 'field
    ; fset : 'record -> 'field -> 'record
    }

  val opaque_identity : 'a -> 'a
end
(**/**)

(** ['record] is the type of the record.  ['field] is the type of the
    values stored in the record field with name [name]. ['perm] is a way
    of restricting the operations that can be used. *)
type ('perm, 'record, 'field) t_with_perm =
  | Field of ('perm, 'record, 'field) For_generated_code.t
[@@unboxed]

The For_generated_code is correctly left out of the documentation, however the t_with_perm type is documented as:

type ('perm, 'record, 'field) t_with_perm =
  | Field of ('perm, 'record, 'field) For_generated_code.t

with For_generated_code.t a dead link. It should instead be documented as:

type ('perm, 'record, 'field) t_with_perm