Nested module comment scope differs between before/after decl

[dsheets]

type t

(** This module has {{!t}type t}! *)
module M : sig
  type t
end

is scoped to the container but

type t

module M : sig
  (** This module has {{!t}type t}! *)

  type t
end

is scoped to the child, M.

See also dsheets/ocamlary-test-library@f326339.

[lpw25]

This is an interesting variation on #15. It seems that we would like self-reference to subcomponents to be highest priority but self-reference to the same definition to be lowest priority.

[dsheets]

I think the rules for the second case work ok. As far as I understand them, the path is searched ancestor-ward starting with self.

I don't understand why the first case is different as I thought both resulted in an annotation node on the same signature item (M).

[lpw25]

I think that the second one is a stand-alone comment within M rather than it's description. I think that only the top-level modules treat the first comment specially. To be honest I can't actually remember whether this is the case, nor whether this is what ocamldoc currently implements, but I think it is probably the right implementation.

[dsheets]

This affects documentation of cmdliner.