Module abbreviation

[Romain Bardou <romain@bardou.fr>]

Hello, dear Caml-list,

I have a file ast.mli. It has no .ml implementation as it contains only
type definitions.

I have a file toto.ml, which contains simply:

module A = Ast

So I only use it as an abbreviation, to write A.t instead of Ast.t for
instance.

However, at link-time, the following error occurs:

File "_none_", line 1, characters 0-1:
Error: Error while linking toto.cmo:
Reference to undefined global `Ast'

I found a workaround, which is to change ast.mli to put all type
definitions in a signature, such as:

module type Sig =
sig
  type t = ...
  ...
end

And then, in toto.ml:

module type A =
sig
  include Ast.Sig
end

Is there any better way to write such a module abbreviation, without
changing ast.mli? And, of course, without copying or renaming ast.mli
into ast.ml.

By the way, this is yet another evidence for the need of a construction
"sig of" which would take a module (with or without implementation) and
return its signature.

Thanks,

-- 
Romain Bardou