QItemSelectionRange: add nothrow member-swap

Change-Id: Ie550f4a66b3c623b0ec630c18f38bcd96f6bbc99
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

src/corelib/itemmodels/qitemselectionmodel.cpp

@@ -103,6 +103,14 @@ QT_BEGIN_NAMESPACE
     by the model index \a index.
 */
 
+/*!
+    \fn QItemSelectionRange::swap(QItemSelectionRange &other)
+    \since 5.6
+
+    Swaps this selection range's contents with \a other.
+    This function is very fast and never fails.
+*/
+
 /*!
     \fn int QItemSelectionRange::top() const
 

src/corelib/itemmodels/qitemselectionmodel.h

@@ -55,6 +55,12 @@ public:
     explicit inline QItemSelectionRange(const QModelIndex &index)
         { tl = index; br = tl; }
 
+    void swap(QItemSelectionRange &other) Q_DECL_NOTHROW
+    {
+        qSwap(tl, other.tl);
+        qSwap(br, other.br);
+    }
+
     inline int top() const { return tl.row(); }
     inline int left() const { return tl.column(); }
     inline int bottom() const { return br.row(); }