[all-commits] [llvm/llvm-project] 4b7bad: [libc++] Implement D2351R0 "Mark all library stati...

[Quuxplusone via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4b7bad9eaea2233521a94f6b096aaa88dc584e23
      https://github.com/llvm/llvm-project/commit/4b7bad9eaea2233521a94f6b096aaa88dc584e23
  Author: Arthur O'Dwyer <arthur.j.odwyer at gmail.com>
  Date:   2021-04-12 (Mon, 12 Apr 2021)

  Changed paths:
    M libcxx/docs/UsingLibcxx.rst
    M libcxx/include/cstddef
    M libcxx/include/functional
    M libcxx/include/type_traits
    M libcxx/include/utility
    M libcxx/test/libcxx/diagnostics/nodiscard_extensions.pass.cpp
    M libcxx/test/libcxx/diagnostics/nodiscard_extensions.verify.cpp
    M libcxx/test/std/utilities/utility/forward/forward.fail.cpp

  Log Message:
  -----------
  [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