More errors with unboxed and untagged attributes

This commit adds errors for bad uses of @untagged and
@unboxed attributes in external declarations.

There are three possible new errors:
  - One when the external does not contain a native version of
the primitive,
  - One when the attribute occurs deeply into the type,
  - One when the attribute is applied to the whole function type.

1 files changed, 10 insertions, 0 deletions

diff --git a/typing/primitive.ml b/typing/primitive.ml
index efe55b1387..74d6eba1c9 100644
--- a/typing/primitive.ml
+++ b/typing/primitive.ml
@@ -34,6 +34,7 @@ type description =
 type error =
   | Old_style_float_with_native_repr_attribute
   | Old_style_noalloc_with_noalloc_attribute
+  | No_native_primitive_with_repr_attribute
 
 exception Error of Location.t * error
 
@@ -113,6 +114,11 @@ let parse_declaration valdecl ~native_repr_args ~native_repr_res =
     Location.prerr_warning valdecl.pval_loc
       (Warnings.Deprecated "[@@noalloc] should be used instead of \
                             \"noalloc\"");
+  if native_name = "" &&
+     not (List.for_all is_ocaml_repr native_repr_args &&
+          is_ocaml_repr native_repr_res) then
+    raise (Error (valdecl.pval_loc,
+                  No_native_primitive_with_repr_attribute));
   let noalloc = old_style_noalloc || noalloc_attribute in
   let native_repr_args, native_repr_res =
     if old_style_float then
@@ -200,6 +206,10 @@ let report_error ppf err =
   | Old_style_noalloc_with_noalloc_attribute ->
     Format.fprintf ppf "Cannot use \"noalloc\" in conjunction with \
                         [%@%@noalloc]"
+  | No_native_primitive_with_repr_attribute ->
+    Format.fprintf ppf
+      "The native code version of the primitive is mandatory when \
+       attributes [%@untagged] or [%@unboxed] are present"
 
 let () =
   Location.register_error_of_exn