This paper proposes that we adopt Barry Revzin’s [[P0893R1](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0893r1.html)] (based on my [[P0515R0](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0515r0.pdf)] section 3.3) with refined proposed rules that may address previous concerns, but for now only make the problematic chains deprecated or ill-formed to allow for a transition period.