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, 1 insertions, 1 deletions

diff --git a/kernel/environ.ml b/kernel/environ.ml
index 45dfb22d3..6e5491c0b 100644
--- a/kernel/environ.ml
+++ b/kernel/environ.ml
@@ -436,7 +436,7 @@ let keep_hyps env needed =
 (* Modules *)
 
 let add_modtype mtb env =
-  let mp = mtb.typ_mp in
+  let mp = mtb.mod_mp in
   let new_modtypes = MPmap.add mp mtb env.env_globals.env_modtypes in
   let new_globals = { env.env_globals with env_modtypes = new_modtypes } in
   { env with env_globals = new_globals }