Merge pull request #4 from zeus-cpp/fix-msvc

Drop the requirement of `/Zc:__cplusplus`

README.md

@@ -33,10 +33,10 @@ Feedbacks are welcome.
 
 Table of known compiler status.
 
-| Planned             | Status          | Note                          |
-| ------------------- | --------------- | ----------------------------- |
-| MSVC v142 and later | Fully tested    | `/Zc:__cplusplus` is required |
-| GCC 8 and later     | Slightly tested |                               |
+| Planned             | Status          |
+| ------------------- | --------------- |
+| MSVC v142 and later | Fully tested    |
+| GCC 8 and later     | Slightly tested |
 
 ## Building and testing
 

include/zeus/expected.hpp

@@ -10,11 +10,17 @@
 #define ZEUS_EXPECTED_VERSION_MINOR 0
 #define ZEUS_EXPECTED_VERSION_PATCH 2
 
-#if __cplusplus < 201'703L
+#if defined(_MSVC_LANG)
+    #define ZEUS_EXPECTED_CPLUSPLUS _MSVC_LANG
+#else
+    #define ZEUS_EXPECTED_CPLUSPLUS __cplusplus
+#endif
+
+#if ZEUS_EXPECTED_CPLUSPLUS < 201'703L
 static_assert(false, "This expected variant requires C++17");
 #endif
 
-#if __cplusplus >= 202'002L
+#if ZEUS_EXPECTED_CPLUSPLUS >= 202'002L
     #define ZEUS_EXPECTED_CONSTEXPR_DTOR constexpr
 #else
     #define ZEUS_EXPECTED_CONSTEXPR_DTOR
@@ -53,7 +59,7 @@ namespace expected_detail
 template<class T, class... Args>
 constexpr T *construct_at(T *p, Args &&...args) noexcept(noexcept(::new (static_cast<void *>(p)) T(std::forward<Args>(args)...)))
 {
-#if __cplusplus >= 202'002L
+#if ZEUS_EXPECTED_CPLUSPLUS >= 202'002L
     return std::construct_at(p, std::forward<Args>(args)...);
 #else
     return ::new (static_cast<void *>(p)) T(std::forward<Args>(args)...);

tests/CMakeLists.txt

@@ -1,7 +1,2 @@
-if (MSVC)
-    add_compile_options(/Zc:__cplusplus)
-    add_compile_options(/W4)
-endif ()
-
 add_subdirectory(test_expected)
 add_subdirectory(third_party)

tests/test_expected/base_tests.cpp

@@ -1,4 +1,5 @@
 #include <string>
+#include <optional>
 
 #include <catch2/catch_all.hpp>