[Caml-list] In 3.12 and 4.0, erratic message "The implementation tt.ml does not match the interface tt.cmi"

[Jean-Louis Giavitto <jean-louis.giavitto@ircam.fr>]

Hello.
if anyone could give me some hints on the following problem...


I have a file tt.ml which reduces to

   type typedef = {
     isa : 'a 'rep 'cell .
       (('rep, int, int, int, int, int) #Collection.collection as 'a);
   }

The mli file is exactly the same has the ml file. 'collection' is a 
virtual class declared in file collection.ml and signature in 
collection.mli.

tt.ml compile without problems. However, if I replace (in tt.ml and 
tt.mli) one of the 'int' parameter by a type variable:

  type typedef = {
   isa :
     'a 'rep 'cell .
       (('rep, 'cell, int, int, int, int) #Collection.collection
        as 'a);
  }

then I have the following message (with the 4.0 compiler):

File "tt.ml", line 1:
Error: The implementation tt.ml does not match the interface tt.cmi:
        Type declarations do not match:
          type typedef = {
            isa :
              'a 'rep 'cell.
          ('rep, 'cell, int, int, int, int) #Collection.collection as 'a;
          }
        is not included in
          type typedef = {
            isa :
              'a 'rep 'cell.
          ('rep, 'cell, int, int, int, int) #Collection.collection as 'a;
          }
        File "tt.ml", line 2, characters 5-112: Actual declaration
        The types for field isa are not equal.


- The problem appears with the compiler 3.12 but also 4.0 (a similar 
error (5622) was reported but was not reproducible with 4.0).
- I have no problem if I drop the .mli file.
- The error seems sensitive to the definition of the class 'collection': 
I was not able to reproduce it with a much simpler definition of 
collection.
- I have the same error if I replace more 'int' parameter by type 
variables.

Have you any clues?
Jean-Louis Giavitto.