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, 2 insertions, 2 deletions

diff --git a/library/declaremods.ml b/library/declaremods.ml
index 5c245064f..68cb81f1a 100644
--- a/library/declaremods.ml
+++ b/library/declaremods.ml
@@ -382,7 +382,7 @@ let rec replace_module_object idl mp0 objs0 mp1 objs1 =
 
 let type_of_mod mp env = function
   |true -> (Environ.lookup_module mp env).mod_type
-  |false -> (Environ.lookup_modtype mp env).typ_expr
+  |false -> (Environ.lookup_modtype mp env).mod_type
 
 let rec get_module_path = function
   |MEident mp -> mp
@@ -527,7 +527,7 @@ let build_subtypes interp_modast env mp args mtys =
        let inl = inl2intopt ann in
        let mte,_ = interp_modast env ModType m in
        let mtb = Mod_typing.translate_modtype env mp inl ([],mte) in
-       { mtb with typ_expr = mk_funct_type env args mtb.typ_expr })
+       { mtb with mod_type = mk_funct_type env args mtb.mod_type })
     mtys