59       // Concrete tag should be BarrierSet::CardTableExtension.

    59       BarrierSet::FakeRtti(BarrierSet::CardTableExtension))

    60       // That will presently break things in a bunch of places though.

    61       // The concrete tag is used as a dispatch key in many places, and

    62       // CardTableExtension does not correctly dispatch in some of those

    63       // uses. This will be addressed as part of a reorganization of the

    64       // BarrierSet hierarchy.

    65       BarrierSet::FakeRtti(BarrierSet::CardTableModRef, 0).add_tag(BarrierSet::CardTableExtension))