[wg-camlp4] Keeping attributes in .cmi files?

[Alain Frisch]

Dear all,

Attributes are currently kept in .cmt and .cmti files, which are dumps 
of the Typedtree counterparts of .ml and .mli files.  This allows 
external tools to access those attributes together with the output of 
the type-checker.  But this does not easily allow the compiler itself 
(which doesn't parse the .cmti file) to see attributes from external units.

If we keep attributes also in the internal structure of the 
type-checker, which is dumped in the .cmi file, we can make the compiler 
aware, for instance, of attributes put on value declarations.

As an example, see the following discussion about having the compiler 
report a warning when a value marked as deprecated is being used:

http://caml.inria.fr/mantis/view.php?id=5854

Attributes give a natural way to mark values as deprecated, and as I 
suggest in the discussion, the simplest way to use this information is 
to keep it in the Types.value_description record (and thus in .cmi files).

If we start having the compiler understand some specific attributes, it 
makes sense, in my opinion, to keep them even in .cmi files (at least 
for attributes on "declarations", not necessarily on type expressions). 
  Do you agree?  Would anyone object to the patch I proposed on the 
ticket above?


Alain