[Caml-list] type constructor escape its scope

[Caml-list] type constructor escape its scope

[Basile STARYNKEVITCH]

Hello List,

[[I'm a bit sick today so brain is badly working... probably a trivial
question I would be ashamed to ask on normal days.. sorry...]]

I compile a selfcontained camlp4 stuff.

You can get it from 

http://www2.poesia-filter.org:8000/cgi-bin/cvsweb.cgi/~checkout~/PoesiaSoft/PoesiaMonIcap/pa_filtproto.ml?rev=1.3&content-type=text/plain

It is the pa_filtproto.ml file in PoesiaSoft/PoesiaMonIcap/ revision
1.3 under CVS on www.poesia-filter.org

I've got when compiling with  
  ocamlc -pp "camlp4o pa_extend.cmo" -I +camlp4 -I . -c pa_filtproto.ml 
the strange message 

File "pa_filtproto.ml", line 60, characters 7-41:
This expression has type definition_t but is here used with type 'a
The type constructor definition_t would escape its scope

However, definition_t is a type defined in line 37 of the same file

any clues?

Thanks....


N.B. Any opinions expressed here are only mine, and not of my organization.
N.B. Les opinions exprimees ici me sont personnelles et n engagent pas le CEA.

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Basile STARYNKEVITCH   ----  Commissariat à l Energie Atomique * France
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home email: Basile at Starynkevitch point net

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Re: [Caml-list] type constructor escape its scope

[Daniel de Rauglaudre]

Hi,

On Thu, Oct 03, 2002 at 11:18:18AM +0200, Basile STARYNKEVITCH wrote:

> I've got when compiling with  
>   ocamlc -pp "camlp4o pa_extend.cmo" -I +camlp4 -I . -c pa_filtproto.ml 
> the strange message 
> 
> File "pa_filtproto.ml", line 60, characters 7-41:
> This expression has type definition_t but is here used with type 'a
> The type constructor definition_t would escape its scope

This happens typically in this situation:
      $ cat foo.ml
      let x = ref [];;
      type t = C;;
      x := [C];;

      $ ocamlc -c foo.ml
      File "foo.ml", line 3, characters 6-7:
      This expression has type t but is here used with type 'a
      The type constructor t would escape its scope

The problem is that at the *definition* of "x", the type "t" does
not exist yet. The type of "x" is deferred, but is actually
"t list ref". But, since "t" is defined after, it would not be
possible to defined it with a type constraint:
      let x = ref ([] : t list);;

I did not look at your example, but search something around that. If it
is some obscur code generated by Camlp4, it can be more difficult: in
this case, I can look at it, if you need.

-- 
Daniel de RAUGLAUDRE
daniel.de_rauglaudre@inria.fr
http://cristal.inria.fr/~ddr/
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