return nsPromiseConcatenation<CharT>(lhs, rhs);
return nsPromiseConcatenation<CharT>(*this, rhs, mFragmentIdentifierMask<<1);
operator+( const basic_nsLiteralString<CharT>& lhs, const basic_nsLiteralString<CharT>& rhs )  {    return nsPromiseConcatenation<CharT>(lhs, rhs);  }