templateStart = placeholderStart + 2;
    }
    builder.append(template, templateStart, template.length());

    // if we run out of placeholders, append the extra args in square brackets
    if (i < args.length) {
      String prefix = " [";
      for (; i < args.length; i++) {
        builder.append(prefix);
        builder.append(lenientToString(args[i]));
        prefix = ", ";
      }