Hardened preconditions for indirect and polymorphic R0 C++26 introduced two new “vocabulary types for composite class design”, `std::indirect` and `std::polymorphic`, via [[P3019R14]](https://wg21.link/p3019r14). Authors Tristan Brindle, Jonathan Coe, Antony Peacock Mailing 2026-09 Doc date 2026-08-21 Audience LEWG P
