tree 1071d38902d2a2b2f5b9fc3257c50d5c3b3b4c0d
parent d7eb797ea55c76c7a71886343e216be27d5757be
author Arthur O'Dwyer <arthur.j.odwyer@gmail.com> 1617648963 -0400
committer Arthur O'Dwyer <arthur.j.odwyer@gmail.com> 1618244955 -0400

[libc++] Implement D2351R0 "Mark all library static cast wrappers as [[nodiscard]]"

These [[nodiscard]] annotations are added as a conforming extension;
it's unclear whether the paper will actually be adopted and make them
mandatory, but they do seem like good ideas regardless.

https://isocpp.org/files/papers/D2351R0.pdf

This patch implements the paper's effect on:
- std::to_integer, std::to_underlying
- std::forward, std::move, std::move_if_noexcept
- std::as_const
- std::identity

The paper also affects (but libc++ does not yet have an implementation of):
- std::bit_cast

Differential Revision: https://reviews.llvm.org/D99895