Print () instead of Doc.nil

Author: shulhi

compiler/syntax/src/res_printer.ml

@@ -834,8 +834,10 @@ and print_mod_type ~state mod_type cmt_tbl =
                                  print_attributes ~state attrs cmt_tbl
                                in
                                let lbl_doc =
-                                 if lbl.Location.txt = "_" || lbl.txt = "*" then
-                                   Doc.nil
+                                 if lbl.Location.txt = "_" then Doc.nil
+                                 else if lbl.txt = "*" then
+                                   let doc = Doc.text "()" in
+                                   print_comments doc cmt_tbl lbl.loc
                                  else
                                    let doc = Doc.text lbl.txt in
                                    print_comments doc cmt_tbl lbl.loc