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🐛 Fix constexpr detection #262

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Merged
merged 1 commit into from
Aug 13, 2025
Merged

🐛 Fix constexpr detection #262

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32 changes: 15 additions & 17 deletions include/stdx/utility.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -277,26 +277,23 @@ template <typename T> constexpr auto is_ct_v<T const> = is_ct_v<T>;
}([&]() constexpr { return __VA_ARGS__; })
#endif

#ifndef CX_DETECT
#ifdef __clang__
#define CX_DETECT(...) \
std::is_empty_v<decltype([&] { \
return (__VA_ARGS__) + ::stdx::cxv_detail::type_val{}; \
})>
#else
namespace stdx {
inline namespace v1 {
template <auto> constexpr auto cx_detect0() {}
constexpr auto cx_detect1(auto) { return 0; }
namespace cxv_detail {
template <auto> constexpr auto cx_sfinae = std::true_type{};

#ifdef __clang__
auto cx_detect(auto f) -> decltype(cx_sfinae<from_any{f()}>);
auto cx_detect(...) -> std::false_type;
#else
auto cx_detect(auto f) {
constexpr auto b = requires { cx_sfinae<from_any{f()}>; };
return std::bool_constant<b>{};
}
#endif
} // namespace cxv_detail
} // namespace v1
} // namespace stdx
#define CX_DETECT(...) \
requires { \
::stdx::cx_detect0<::stdx::cx_detect1( \
(__VA_ARGS__) + ::stdx::cxv_detail::type_val{})>; \
}
#endif
#endif

#ifndef CX_WRAP
#define CX_WRAP(...) \
Expand All @@ -310,7 +307,8 @@ constexpr auto cx_detect1(auto) { return 0; }
std::is_empty_v< \
std::invoke_result_t<decltype(f)>>) { \
return f(); \
} else if constexpr (CX_DETECT(__VA_ARGS__)) { \
} else if constexpr (decltype(::stdx::cxv_detail::cx_detect( \
f))::value) { \
return ::stdx::overload{::stdx::cxv_detail::cx_base{}, f}; \
} else { \
return f(); \
Expand Down
22 changes: 21 additions & 1 deletion test/utility.cpp
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Expand Up @@ -317,6 +317,26 @@ TEST_CASE("CX_WRAP string_view runtime arg", "[utility]") {
CHECK(CX_WRAP(x) == std::string_view{"hello"});
}

namespace {
auto at_init_time() { return 17; }
auto nc_var = at_init_time();
} // namespace

TEST_CASE("CX_WRAP static runtime arg", "[utility]") {
STATIC_REQUIRE(std::is_same_v<decltype(CX_WRAP(nc_var)), decltype(nc_var)>);
CHECK(CX_WRAP(nc_var) == 17);
}

namespace {
constexpr auto at_compile_time() { return 17; }
constexpr auto c_var = at_compile_time();
} // namespace

TEST_CASE("CX_WRAP static constexpr arg", "[utility]") {
STATIC_REQUIRE(stdx::is_cx_value_v<decltype(CX_WRAP(c_var))>);
STATIC_REQUIRE(CX_WRAP(c_var)() == 17);
}

TEST_CASE("CX_WRAP const integral type", "[utility]") {
auto const x = 17;
STATIC_REQUIRE(stdx::is_cx_value_v<decltype(CX_WRAP(x))>);
Expand Down Expand Up @@ -378,7 +398,7 @@ TEST_CASE("CX_WRAP integral_constant arg", "[utility]") {
#ifdef __clang__
namespace {
struct expression_test {
int f(int x) { return x; }
auto f(int x) -> int { return x; }
};
} // namespace

Expand Down