[Qt5-feedback] Add internalVariant to QModelIndex

[Stephen Kelly]

Nils Jeisecke wrote:

>> I don't know what assert you mean here, and I know of nothing in the code
>> preventing you from creating two QModelIndexes with different internal
>> pointers and referring to the same item. I also know that you can create
>> QModelIndexes dynamically and you don't have to keep them around.
> 
> see QAbstractItemView::setModel(QAbstractItemModel *model)
> 
>     // These asserts do basic sanity checking of the model
>     Q_ASSERT_X(d->model->index(0,0) == d->model->index(0,0),
>                "QAbstractItemView::setModel",
>                "A model should return the exact same index "
>                "(including its internal id/pointer) when asked for it
> twice in a row.");
> 
> Nils

Oh, ok. I thought you meant something different about accessing the actual 
data. 

I still don't see why you would want d->model->index(0,0) != d->model-
>index(0,0) though and why you think it means you have to keep already 
created indexes around.

I would like to see a minimal or partial implementation which shows that 
requirement.