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Recursive module and class
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Date: -- (:)
From: Jun Furuse <jun.furuse@g...>
Subject: Recursive module and class
Hi,

Sorry if the following is already a known issue.

The following program trying to define a type and a class mutually recursive
is rejected by ocamlc (3.11+dev12 Private_abbrevs+natdynlink (2008-02-29)):

       module rec M : sig
         type t = Foo of N.c
       end = struct
         type t = Foo of N.c
       end and N : sig
         class c : object method x : M.t end
       end = struct
         class c = object (self)
           method x = M.Foo (self :> c)
         end
       end

The error message is puzzling:

       Error: Signature mismatch:
              Modules do not match:
                sig class c : object method x : M.t end end
              is not included in
                sig class c : object method x : M.t end end
              Type declarations do not match:
                type c = N.c
              is not included in
                type c = < x : M.t >

These signatures are literaly same, but do not match.

The above code is accepted by the compiler if I write

           method x = M.Foo (self :> N.c)

to coerce the object to the outer class N.c instead of c.

Is it a bug of typing? Or is it ok but with a puzzling error message ?

--
Jun FURUSE