Conflicting treatment of gridview/indexset in mappers

The MultipleCodimMultipleGeomTypeMapper internally stores

// GridView is needed to keep the IndexSet valid
GV gridView_;
const typename GV::IndexSet& is;

a grid view and a reference to an indexset and there is an interesting comment where I don't know if the statement is correct. In the update method since recently, the gridview is updated, e.g.

void update (const GV& gridView)
{
  gridView_ = gridView;
  update_();
}

But the reference to the index set is not updated.

The SingleCodimSingleGeomTypeMapper stores a pointer

const typename GV::IndexSet* is_;

So apparently no gridview is needed here to keep the pointer alive. Also update just sets the pointer

void update (const GV& gridView)
{
  is_ = &gridView.indexSet();
}

without storing the gridview itself.

What are the correct guarantees offered by the interface? The implementations seem to contradict each other, so at least one of them should be buggy.

I think this should be resolved before release 2.8 since the new mapper.update(gridView) interfaces have just been introduced recently and this might be related.