QSqlQueryModel: restore RVO in data()

The return of a default-constructed QVariant 'v' from three branches
invites NRVO, but most compilers won't let it kick in, because there
are two return statements that don't return 'v'.

Return an rvalue from each branch, so RVO is guaranteed (since C++17)
to kick in.

Amends the start of the public history.

Picking back all the way, since it's risk-free.

Pick-to: 6.5 5.15
Change-Id: I495885bee3ebba63c9e52640903c792011c1dee2
Reviewed-by: Christian Ehrlicher <[email protected]>
(cherry picked from commit 26ba78900d6dae5be24b83004f0f91db74ac95e4)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>
(cherry picked from commit 89bc556da09759933f4f0773a85bfd70ce6b3c5e)

1 files changed, 3 insertions, 4 deletions

diff --git a/src/sql/models/qsqlquerymodel.cpp b/src/sql/models/qsqlquerymodel.cpp
index 1aae088c64a..f109f042f16 100644
--- a/src/sql/models/qsqlquerymodel.cpp
+++ b/src/sql/models/qsqlquerymodel.cpp
@@ -329,19 +329,18 @@ QVariant QSqlQueryModel::data(const QModelIndex &item, int role) const
     if (!item.isValid())
         return QVariant();
 
-    QVariant v;
     if (role & ~(Qt::DisplayRole | Qt::EditRole))
-        return v;
+        return QVariant();
 
     if (!d->rec.isGenerated(item.column()))
-        return v;
+        return QVariant();
     QModelIndex dItem = indexInQuery(item);
     if (dItem.row() > d->bottom.row())
         const_cast<QSqlQueryModelPrivate *>(d)->prefetch(dItem.row());
 
     if (!d->query.seek(dItem.row())) {
         d->error = d->query.lastError();
-        return v;
+        return QVariant();
     }
 
     return d->query.value(dItem.column());