Separating the module_type and module_body types by using a type parameter.

As explained in edf85b9, the original commit that merged the module_body
and module_type_body representations, this was delayed to a later time
assumedly due to OCaml lack of GADTs. Actually, the only thing that was
needed was polymorphic recursion, which has been around already for a
relatively long time (since 3.12).

1 files changed, 12 insertions, 6 deletions

diff --git a/checker/declarations.ml b/checker/declarations.ml
index 093d999a3..884a1ef18 100644
--- a/checker/declarations.ml
+++ b/checker/declarations.ml
@@ -583,24 +583,30 @@ let rec subst_expr sub = function
   | MEwith (me,wd)-> MEwith (subst_expr sub me, subst_with_body sub wd)
 
 let rec subst_expression sub me =
-  functor_map (subst_module sub) (subst_expr sub) me
+  functor_map (subst_module_type sub) (subst_expr sub) me
 
 and subst_signature sub sign =
-  functor_map (subst_module sub) (subst_structure sub) sign
+  functor_map (subst_module_type sub) (subst_structure sub) sign
 
 and subst_structure sub struc =
   let subst_body = function
     | SFBconst cb -> SFBconst (subst_const_body sub cb)
     | SFBmind mib -> SFBmind (subst_mind sub mib)
     | SFBmodule mb -> SFBmodule (subst_module sub mb)
-    | SFBmodtype mtb -> SFBmodtype (subst_module sub mtb)
+    | SFBmodtype mtb -> SFBmodtype (subst_module_type sub mtb)
   in
   List.map (fun (l,b) -> (l,subst_body b)) struc
 
-and subst_module sub mb =
+and subst_body : 'a. (_ -> 'a -> 'a) -> _ -> 'a generic_module_body -> 'a generic_module_body =
+  fun subst_impl sub mb ->
   { mb with
     mod_mp = subst_mp sub mb.mod_mp;
-    mod_expr =
-      implem_map (subst_signature sub) (subst_expression sub) mb.mod_expr;
+    mod_expr = subst_impl sub mb.mod_expr;
     mod_type = subst_signature sub mb.mod_type;
     mod_type_alg = Option.smartmap (subst_expression sub) mb.mod_type_alg }
+
+and subst_module sub mb =
+  subst_body (fun sub e -> implem_map (subst_signature sub) (subst_expression sub) e) sub mb
+
+and subst_module_type sub mb =
+  subst_body (fun _ () -> ()) sub mb