P2968R2 Make `std::ignore` A First-Class Object

[frederick-vs-ja]

WG21-P2968R2 Make std::ignore A First-Class Object

No feature-test macro is mentioned.

We're already conforming to the improved specification (except for the location of std::ignore). https://github.com/microsoft/STL/blob/165fc9459c85faa65cd3dec313eb10f55bab154c/stl/inc/tuple#L122-L130

So the only things need to be done are

• moving _Ignore and ignore to <utility>,
• removing the /* strengthened */ comment from the operator=, and
• adding the // P2968R2 Make std::ignore A First-Class Object comment to <yvals_core.h> immediately after this line https://github.com/microsoft/STL/blob/165fc9459c85faa65cd3dec313eb10f55bab154c/stl/inc/yvals_core.h#L81

This issue is intended for a new contributor (especially one new to GitHub) to get started with the simplest possible change.

Please feel free to submit a pull request if there isn't one already linked here - no need to ask for permission! 😸

You can (and should) link your pull request to this issue using GitHub's close/fix/resolve syntax. (in the PR description not the commit message)

[cpplearner]

WG21-P2968R2 requires std::ignore to be available when <utility> is included, which isn't currently the case with MSVC STL.

To implement this, we should move the definition of std::ignore to <utility>.

(Aside: this movement is safe because <tuple> unconditionally includes <__msvc_iter_core.hpp>, which unconditionally includes <utility>.)