Declarations.mli refactoring: module_type_body = module_body

 After this commit, module_type_body is a particular case of module_type.
 For a [module_type_body], the implementation field [mod_expr] is
 supposed to be always [Abstract]. This is verified by coqchk, even
 if this isn't so crucial, since [mod_expr] is never read in the case
 of a module type.

 Concretely, this amounts to the following rewrite on field names
 for module_type_body:
  - typ_expr --> mod_type
  - typ_expr_alg --> mod_type_alg
  - typ_* --> mod_*
 and adding two new fields to mtb:
  - mod_expr (always containing Abstract)
  - mod_retroknowledge (always containing [])

 This refactoring should be completely transparent for the user.

 Pros: code sharing, for instance subst_modtype = subst_module.
 Cons: a runtime invariant (mod_expr = Abstract) which isn't
 enforced by typing. I tried a polymorphic typing of mod_expr,
 to share field names while not having mtb = mb, but the OCaml
 typechecker isn't clever enough with polymorphic mutual fixpoints,
 and reject code sharing (e.g. between subst_modtype and subst_module).
 In the future (with ocaml>=4), some GADT could maybe help here,
 but for now the current solution seems good enough.

1 files changed, 6 insertions, 6 deletions

diff --git a/printing/printmod.ml b/printing/printmod.ml
index 84d4208f9..6b8bdea40 100644
--- a/printing/printmod.ml
+++ b/printing/printmod.ml
@@ -234,12 +234,12 @@ let nametab_register_module_body mp struc =
     nametab_register_dir mp;
     List.iter (nametab_register_body mp DirPath.empty) struc
 
-let get_typ_expr_alg mtb = match mtb.typ_expr_alg with
+let get_typ_expr_alg mtb = match mtb.mod_type_alg with
   | Some (NoFunctor me) -> me
   | _ -> raise Not_found
 
 let nametab_register_modparam mbid mtb =
-  match mtb.typ_expr with
+  match mtb.mod_type with
   | MoreFunctor _ -> () (* functorial param : nothing to register *)
   | NoFunctor struc ->
     (* We first try to use the algebraic type expression if any,
@@ -355,9 +355,9 @@ let rec print_expression x =
 and print_signature x =
   print_functor print_modtype print_structure x
 
-and print_modtype env mp locals mtb = match mtb.typ_expr_alg with
+and print_modtype env mp locals mtb = match mtb.mod_type_alg with
   | Some me -> print_expression true env mp locals me
-  | None -> print_signature true env mp locals mtb.typ_expr
+  | None -> print_signature true env mp locals mtb.mod_type
 
 let rec printable_body dir =
   let dir = pop_dirpath dir in
@@ -415,9 +415,9 @@ let print_modtype kn =
     (keyword "Module Type" ++ spc () ++ name ++ str " =" ++ spc () ++
      (try
 	if !short then raise ShortPrinting;
-	print_signature' true (Some (Global.env ())) kn mtb.typ_expr
+	print_signature' true (Some (Global.env ())) kn mtb.mod_type
       with e when Errors.noncritical e ->
-	print_signature' true None kn mtb.typ_expr))
+	print_signature' true None kn mtb.mod_type))
 
 end