Treat cases with non-unary payloads uniformly.

Author: cristianoc

jscomp/build_tests/super_errors/expected/UntaggedNonUnary2.res.expected

@@ -6,4 +6,4 @@
   2 │ type t = Tuple(int, string) | Float(float)
   3 │ 
 
-  This type cannot be unboxed because it has more than one constructor.
+  This untagged variant definition is invalid: Constructor Tuple has more than one argument.

jscomp/ml/typedecl.ml

@@ -304,27 +304,27 @@ let transl_declaration ~typeRecordAsObject env sdecl id =
   in
   let raw_status = get_unboxed_from_attributes sdecl in
 
-  let checkUntaggedVariant = match sdecl.ptype_kind with
+  let checkUntaggedVariant() = match sdecl.ptype_kind with
   | Ptype_variant cds -> Ext_list.for_all cds (function
       | {pcd_args = Pcstr_tuple ([] | [_])} ->
         (* at most one payload allowed for untagged  variants *)
         true
+      | {pcd_args = Pcstr_tuple (_::_::_); pcd_name={txt=name}} ->
+        Ast_untagged_variants.reportConstructorMoreThanOneArg ~loc:sdecl.ptype_loc ~name
       | {pcd_args = Pcstr_record _} -> true
-      | _ -> false )
+     )
   | _ -> false
   in
 
-  if raw_status.unboxed && not raw_status.default && not checkUntaggedVariant then begin
+  if raw_status.unboxed && not raw_status.default && not (checkUntaggedVariant()) then begin
     match sdecl.ptype_kind with
     | Ptype_abstract ->
         raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                       "it is abstract"))
     | Ptype_variant [{pcd_args = Pcstr_tuple []}] ->
       raise(Error(sdecl.ptype_loc, Bad_unboxed_attribute
                     "its constructor has no argument"))
-    | Ptype_variant [{pcd_args = Pcstr_tuple [_]}] -> ()
-    | Ptype_variant [{pcd_args = Pcstr_tuple (_::_::_); pcd_name = {txt=name}}] ->
-      Ast_untagged_variants.reportConstructorMoreThanOneArg ~loc:sdecl.ptype_loc ~name
+    | Ptype_variant [{pcd_args = Pcstr_tuple _}] -> ()
     | Ptype_variant [{pcd_args = Pcstr_record
                         [{pld_mutable=Immutable; _}]}] -> ()
     | Ptype_variant [{pcd_args = Pcstr_record [{pld_mutable=Mutable; _}]}] ->