Method swap

extlibs/catch/include/catch/catch.hpp:13275–13279

    }

    void StringRef::swap( StringRef& other ) noexcept {
        std::swap( m_start, other.m_start );
        std::swap( m_size, other.m_size );
        std::swap( m_data, other.m_data );
    }

    auto StringRef::c_str() const -> char const* {
        if( !isSubstring() )