QDataStream setDevice() doesn't work on a default contructed QDataStream Object

Here is a simple program I wrote, that, in theory, should compile without issues. I create an object using the QDataStream Default constructor.

#include <QtCore/QDataStream>
#include <QtCore/QIODevice>
#include <QtCore/QFile>
int main( int argc, char **argv )
{
 QDataStream out_stream(); // we will serialize the data into the file
 QFile file("file.dat");
 file.open(QIODevice::WriteOnly);
 out_stream.setDevice(&file);
}
 

When attempting to compile this program, I get the following error:

datastream_test.cpp: In function 'int main(int, char**)':
datastream_test.cpp:12:16: error: request for member 'setDevice' in 'out_stream', which is of non-class type 'QDataStream()'
     out_stream.setDevice(&file);
                ^~~~~~~~~

This error makes no sense, as out is initialized as a QDataStream object. From what I can tell, calling the QDataStream constructor without passing an argument results in  an object ("out_stream") that is not initialized as a QDataStream object.

The only way I can use setDevice successfully is by passing a QIODevice into the QDataStream constructor. This is demonstrated in the below code, which compiles without issues:

#include <QtCore/QDataStream>
#include <QtCore/QIODevice>
#include <QtCore/QFile>
int main( int argc, char **argv )
{
 QFile dummy_file("asdf.dat");    //dummy that is used to initialize the datastream object
 dummy_file.open(QIODevice::WriteOnly);
 QDataStream out_stream(); // we will serialize the data into the file
 QFile file("file.dat");
 file.open(QIODevice::WriteOnly);
 out_stream.setDevice(&file);
}

This workaround gets Qt to (correctly) recognize "out_stream" as a QDataStream object. However, calling the QDataStream Constructor without passing arguments does not result in an object that is recognized as a QDataStream object.

When I create a default constructed QDatastream object and try to call setDevice() on it, I get