Infinite cycle due to QTextStream

So, I get infinite cycle while trying to read lines from file (line by line). I was trying to use do{}while(); cycle like that:

QTextStream stream(stdin);
QString line;
do {
    line = stream.readLine();
} while (!line.isNull()); 

but I get empty string.

Sure, I checked file path (it is right). I was trying to use /Users/user/tts.txt path but without changes. I was trying to read other files (like m3u). And it's not working on macOS Catalina, Windows 10, Linux (Debian).

So, why did I get infinite cycle?

QStringList Manager::GetLinesFromFile(const QString &nameOfFile)
{
    QStringList lines = {};

    //path to file
    const QString path = QCoreApplication::applicationDirPath() + "/bin/" + "tts.txt";
    //"/Users/user/tts.txt"

    QFile buffer;
    buffer.QFile::setFileName(path);

    #ifndef Q_DEBUG
    qDebug() << path;
    #endif

    if(buffer.QFile::exists())
    {
        if(!buffer.QIODevice::open(QIODevice::ReadOnly))
        {
            #ifndef Q_DEBUG
            qCritical() << "error: can't open file";
            #endif
        }
        else
        {
            QTextStream stream(&buffer);

             // both conditions
            // (!stream.QTextStream::atEnd()) 
            while(!buffer.QFileDevice::atEnd())
                lines.QList::push_back(stream.QTextStream::readLine());

            buffer.QFile::close();
        }
    }
    else
    {
        #ifndef Q_DEBUG
        qCritical() << "error: file not exists";
        #endif
    }

    return lines;
}

So, I got it. I opened the file incorrectly.

I was using:

if(!file.QIODevice::open(QIODevice::ReadOnly))

but it should be like that:

if(!file.QFile::open(QFile::ReadOnly))