message: Error out when loading a malformed saved model that requires a reference to a reference of a variable.
diff: @@ -487,6 +487,11 @@ Status AddArgToSig(const NodeDefOrAttrSlice& node_or_attrs,
  if (arg_def.is_ref()) {
  // For all types that were added by this function call, make them refs.
  for (size_t i = original_size; i < sig->size(); ++i) {
  + if (IsRefType((*sig)[i])) {
  + return errors::InvalidArgument(
  + "Requested reference to a reference type: ",
  + arg_def.ShortDebugString());
  + }
  (*sig)[i] = MakeRefType((*sig)[i]);
  }
  }
  