[libcxx-commits] [libcxx] [libc++][test] Mark `optional` test functions as `TEST_CONSTEXPR_CXX20` (PR #94172)

[Stephan T. Lavavej via libcxx-commits]

https://github.com/StephanTLavavej created https://github.com/llvm/llvm-project/pull/94172

[P2231R1](https://wg21.link/P2231R1) "Missing `constexpr` in `std::optional` and `std::variant`" was accepted as a C++20 Defect Report, not a C++17 Defect Report. Accordingly, `test_empty_emplace()` and `check_reset()` should be marked as `TEST_CONSTEXPR_CXX20`. Note that their `static_assert`s are properly guarded:

https://github.com/llvm/llvm-project/blob/4ce65423be0ba1d90c11b6a79981d6314e1cf36d/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace.pass.cpp#L270-L272

https://github.com/llvm/llvm-project/blob/4ce65423be0ba1d90c11b6a79981d6314e1cf36d/libcxx/test/std/utilities/optional/optional.object/optional.object.mod/reset.pass.cpp#L53-L55

Found while running libc++'s tests with MSVC's STL, as we activate our `constexpr` here for C++20 and above.

>From 24b1a67c8daac22addb6740de2457e16f3123dd3 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl at nuwen.net>
Date: Sun, 2 Jun 2024 14:06:52 -0700
Subject: [PATCH] Mark `test_empty_emplace()` and `check_reset()` as
 `TEST_CONSTEXPR_CXX20`.

---
 .../optional.object/optional.object.assign/emplace.pass.cpp     | 2 +-
 .../optional/optional.object/optional.object.mod/reset.pass.cpp | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace.pass.cpp b/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace.pass.cpp
index 17a1e94b0ba6e..631052cad94b9 100644
--- a/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace.pass.cpp
+++ b/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace.pass.cpp
@@ -210,7 +210,7 @@ void test_on_test_type() {
     }
 }
 
-constexpr bool test_empty_emplace()
+TEST_CONSTEXPR_CXX20 bool test_empty_emplace()
 {
     optional<const int> opt;
     auto &v = opt.emplace(42);
diff --git a/libcxx/test/std/utilities/optional/optional.object/optional.object.mod/reset.pass.cpp b/libcxx/test/std/utilities/optional/optional.object/optional.object.mod/reset.pass.cpp
index 112ee213b42a6..c8c0b01060608 100644
--- a/libcxx/test/std/utilities/optional/optional.object/optional.object.mod/reset.pass.cpp
+++ b/libcxx/test/std/utilities/optional/optional.object/optional.object.mod/reset.pass.cpp
@@ -31,7 +31,7 @@ struct X
 
 bool X::dtor_called = false;
 
-constexpr bool check_reset()
+TEST_CONSTEXPR_CXX20 bool check_reset()
 {
     {
         optional<int> opt;