[all-commits] [llvm/llvm-project] 546449: [libcxx][optional] adds missing constexpr operations

[Christopher Di Bella via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 546449938a39dcc65f60f8d6e44e7b058a026549
      https://github.com/llvm/llvm-project/commit/546449938a39dcc65f60f8d6e44e7b058a026549
  Author: Christopher Di Bella <cjdb at google.com>
  Date:   2021-06-10 (Thu, 10 Jun 2021)

  Changed paths:
    M libcxx/docs/Cxx2aStatusPaperStatus.csv
    M libcxx/include/optional
    M libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace.pass.cpp
    M libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace_initializer_list.pass.cpp
    M libcxx/test/std/utilities/optional/optional.object/optional.object.assign/nullopt_t.pass.cpp
    M libcxx/test/std/utilities/optional/optional.object/optional.object.assign/optional_U.pass.cpp
    M libcxx/test/std/utilities/optional/optional.object/optional.object.ctor/const_optional_U.pass.cpp
    M libcxx/test/std/utilities/optional/optional.object/optional.object.ctor/explicit_const_optional_U.pass.cpp
    M libcxx/test/std/utilities/optional/optional.object/optional.object.ctor/explicit_optional_U.pass.cpp
    M libcxx/test/std/utilities/optional/optional.object/optional.object.ctor/move.fail.cpp
    M libcxx/test/std/utilities/optional/optional.object/optional.object.ctor/optional_U.pass.cpp
    M libcxx/test/std/utilities/optional/optional.object/optional.object.dtor/dtor.pass.cpp
    M libcxx/test/std/utilities/optional/optional.object/optional.object.mod/reset.pass.cpp
    M libcxx/test/std/utilities/optional/optional.object/optional.object.swap/swap.pass.cpp

  Log Message:
  -----------
  [libcxx][optional] adds missing constexpr operations

Makes the following operations constexpr:
  * `std::swap(optional, optional)`
  * `optional(optional<U> const&)`
  * `optional(optional<U>&&)`
  * `~optional()`
  * `operator=(nullopt_t)`
  * `operator=(U&&)`
  * `operator=(optional<U> const&)`
  * `operator=(optional<U>&&)`
  * `emplace(Args&&...)`
  * `emplace(initializer_list<U>, Args&&...)`
  * `swap(optional&)`
  * `reset()`

P2231 has been accepted by plenary, with the committee recommending
implementers retroactively apply to C++20. It's necessary for us to
implement _`semiregular-box`_ and _`non-propagating-cache`_, both of
which are required for ranges (otherwise we'll need to reimplement
`std::optional` with these members `constexpr`ified).

Differential Revision: https://reviews.llvm.org/D102119