test: add tests for LWG-4031

Signed-off-by: Yuming He <ComixHe1895@outlook.com>

Author: ComixHe

tests/test_expected/CMakeLists.txt

@@ -6,6 +6,7 @@ set(SOURCES
     noexcept_tests.cpp
     equality_tests.cpp
     lwg_3886_tests.cpp
+    lwg_4031_tests.cpp
 )
 
 find_package(Catch2 3 REQUIRED)

tests/test_expected/lwg_4031_tests.cpp

@@ -0,0 +1,24 @@
+#include <catch2/catch_all.hpp>
+
+#include <zeus/expected.hpp>
+
+using namespace zeus;
+
+namespace
+{
+// Exposing all members for testing
+struct test_bad_expected_access : public bad_expected_access<void>
+{
+    using bad_expected_access<void>::bad_expected_access;
+};
+}
+
+TEST_CASE("bad_expected_access<void> special members are noexcept", "[LWG-4031]")
+{
+    STATIC_REQUIRE(std::is_nothrow_default_constructible_v<test_bad_expected_access>);
+    STATIC_REQUIRE(std::is_nothrow_copy_constructible_v<test_bad_expected_access>);
+    STATIC_REQUIRE(std::is_nothrow_move_constructible_v<test_bad_expected_access>);
+    STATIC_REQUIRE(std::is_nothrow_copy_assignable_v<test_bad_expected_access>);
+    STATIC_REQUIRE(std::is_nothrow_move_assignable_v<test_bad_expected_access>);
+    STATIC_REQUIRE(std::is_nothrow_destructible_v<test_bad_expected_access>);
+}