QVariant::isNull() must return true for nullptr_t

In Qt 5.8 we see many changes, and one of these is std::nullptr_t became registered type which is meant to be use for null values.

So, for example, if in C++ we get QVariant value from QML, and this value was set to null in QML, then QVariant::isNull() returns false. And user has to write ugly code like this:

if(value.isNull() || static_cast<QMetaType::Type>(value.type()) == QMetaType::Nullptr)
{
    // The value is null, or default object for a type
}
else
{
    // In this branch we can try convert value to C++ types
}

instead of something like this:

if(value.isNull())
{
    // The value is null, or default object for a type
}
else
{
    // In this branch we can try convert value to C++ types
}

Other example is:

int main() {
    QVariant v1 = QVariant::fromValue<void*>(nullptr);
    QVariant v2 = QVariant::fromValue(nullptr);
    qDebug() << v1.isNull() << v2.isNull() << (v1 == v2) << (v2 == v1);
    qDebug() << v2.canConvert<void*>() << v2.canConvert<QObject*>();
}
// output:
// "false false false false" 
// "false false"

I agree with the author of this example (Olivier) and I also think that it is wrong. Because it goes against of semantic of the isNull() method name.
In the discussion there are some posts against Olivier, but I think it is better for future releases to fix it now.

One of the possible solutions is based on the post:

QVariant's only pointer constructor is the one for const char*, which will be
null if the pointer is null too. That would support the proposition that
QVariant(nullptr).isNull() because QVariant((const char*)nullptr).isNull().

However, to create a VoidStar, you need to write:

QVariant::fromValue<void *>(nullptr);

which does

return QVariant(qMetaTypeId<T>(), &t, QTypeInfo<T>::isPointer);

That constructor always sets d.is_null = false. So the QVariant is not null,
as it contains a valid VoidStar value. It just happens that the VoidStar
itself is null. In other words, QVariant behaves like a non-null void**
pointing to a null void*.

So, maybe it should check the pointer value in QVariant(qMetaTypeId<T>(), &t, QTypeInfo<T>::isPointer) constructor and if isPointer and *t is null then set d.is_null = true

P.S. You could read the discussion in these links:
http://lists.qt-project.org/pipermail/development/2016-September/027370.html

http://development.qt-project.narkive.com/YnH0ceXV/behaviour-change-in-qml-in-qt-5-8-regarding-null

P.P.S. I think it must to be fixed before the final release of Qt 5.8.0, because later it will harder to change the behavior in public API, IMHO.