[libc++] Mark LWG3211 as complete: default constructor of tuple<> should be trivial

[jloser]

Summary

libc++ has had the guarantee of the default constructor of tuple<> being
trivial since 405570dc7a95cdf43cdee14b8a9f9c1657a6ad13. Now, the
standard mandates it as of LWG3211. So, move the file out of
libcxx/test/libcxx and into libcxx/test/std since it's no longer
libc++-specific. Rename it to be .compile.pass.cpp instead of
.pass.cpp while we're at it.

[ldionne]

Thanks a lot for the archeology!

[Mordante]

One minor nit, other than that LGTM!

libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/empty_tuple_trivial.compile.pass.cpp

17

Since it's compilation only main can be removed.

[jloser]

libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/empty_tuple_trivial.compile.pass.cpp

17

Good call. I plan on rebasing once CI is fixed/green and then if if this is still green after rebasing, I'll remove the main and land this.

[jloser]

Rebase after CI fixes
Remove main

libcxx/docs/Status/Cxx2bIssues.csv

 "Issue #","Issue Name","Meeting","Status","First released version","Labels"
 "`2839 <https://wg21.link/LWG2839>`__","Self-move-assignment of library types, again","November 2020","",""
 "`3117 <https://wg21.link/LWG3117>`__","Missing ``packaged_task`` deduction guides","November 2020","",""
 "`3143 <https://wg21.link/LWG3143>`__","``monotonic_buffer_resource`` growth policy is unclear","November 2020","",""
 "`3195 <https://wg21.link/LWG3195>`__","What is the stored pointer value of an empty ``weak_ptr``?","November 2020","",""
-"`3211 <https://wg21.link/LWG3211>`__","``std::tuple<>`` should be trivially constructible","November 2020","",""
+"`3211 <https://wg21.link/LWG3211>`__","``std::tuple<>`` should be trivially constructible","November 2020","|Complete|","9.0"
 "`3236 <https://wg21.link/LWG3236>`__","Random access iterator requirements lack limiting relational operators domain to comparing those from the same range","November 2020","","","|ranges|"
 "`3265 <https://wg21.link/LWG3265>`__","``move_iterator``'s conversions are more broken after P1207","November 2020","Fixed by `LWG3435 <https://wg21.link/LWG3435>`__",""
 "`3435 <https://wg21.link/LWG3435>`__","``three_way_comparable_with<reverse_iterator<int*>, reverse_iterator<const int*>>``","November 2020","|Complete|","13.0"
 "`3432 <https://wg21.link/LWG3432>`__","Missing requirement for ``comparison_category``","November 2020","","","|spaceship|"
 "`3447 <https://wg21.link/LWG3447>`__","Deduction guides for ``take_view`` and ``drop_view`` have different constraints","November 2020","|Complete|","14.0"
 "`3450 <https://wg21.link/LWG3450>`__","The const overloads of ``take_while_view::begin/end`` are underconstrained","November 2020","","","|ranges|"
 "`3464 <https://wg21.link/LWG3464>`__","``istream::gcount()`` can overflow","November 2020","",""
 "`2731 <https://wg21.link/LWG2731>`__","Existence of ``lock_guard<MutexTypes...>::mutex_type`` typedef unclear","November 2020","|Complete|","5.0"

libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/empty_tuple_trivial.compile.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// This test ensures that std::tuple<> is trivially constructible. That is not
-// required by the Standard, but libc++ provides that guarantee.
-
 // UNSUPPORTED: c++03
 
 #include <tuple>
 #include <type_traits>
 
 
 static_assert(std::is_trivially_constructible<std::tuple<>>::value, "");
 
 int main(int, char**) {
   return 0;
 }