parser->parseColonType(
                   replicated_region_arg_types.emplace_back())) {
      return failure();
    }
  } while (succeeded(parser->parseOptionalComma()));

  region_args->reserve(replicated_region_args.size() +
                       packed_region_args.size());
  region_args->append(replicated_region_args.begin(),

      l_square_parsed = true;
    }

    do {
      StringRef attr;
      if (failed(parser.parseKeyword(&attr))) return {};
      attrs.push_back(StringAttr::get(ctx, attr));
    } while (succeeded(parser.parseOptionalComma()));

    if (l_square_parsed && failed(parser.parseRSquare())) {
      parser.emitError(parser.getNameLoc(), "expected ']'");
    }

    if (failed(parser.parseGreater())) {