✨ add is_union trait

include/zll/meta/is_union.hpp

@@ -0,0 +1,16 @@
+#ifndef ZLL_META_ISUNION_HPP
+#define ZLL_META_ISUNION_HPP
+
+#include "zll/utils/intrinsics_macros.hpp"
+#include "zll/meta/integral_constant.hpp"
+
+namespace zll {
+namespace meta {
+
+template <typename T>
+struct is_union : bool_constant<ZLL_INTRINSICS_IS_UNION(T)> {};
+
+}  // namespace meta
+}  // namespace zll
+
+#endif  // ZLL_META_ISUNION_HPP

include/zll/type_traits.hpp

@@ -11,6 +11,7 @@
 
 #include "zll/meta/is_pointer.hpp"
 #include "zll/meta/is_same.hpp"
+#include "zll/meta/is_union.hpp"
 
 #include "zll/meta/remove_cv.hpp"
 

include/zll/utils/intrinsics_macros.hpp

@@ -0,0 +1,6 @@
+#ifndef ZLL_UTILS_INTRINSICMACROS_HPP
+#define ZLL_UTILS_INTRINSICMACROS_HPP
+
+#define ZLL_INTRINSICS_IS_UNION(t) __is_union(t) 
+
+#endif // ZLL_UTILS_INTRINSICMACROS_HPP

tests/unit_tests/meson.build

@@ -4,6 +4,7 @@ unit_tests_srcs = [
     'meta/integral_constant_tests.cpp',
     'meta/is_pointer_tests.cpp',
     'meta/is_same_tests.cpp',
+    'meta/is_union_tests.cpp',
     'meta/remove_cv_tests.cpp',
     'main.cpp',
 ]

tests/unit_tests/meta/is_union_tests.cpp

@@ -0,0 +1,24 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include "zll/meta/is_union.hpp"
+
+#include <utest.h>
+
+typedef union {
+    char a;
+    int b;
+} test_union;
+
+struct test_struct {
+    test_union u;
+};
+
+UTEST(meta_is_union, sfinae) {
+    ASSERT_TRUE(zll::meta::is_union<test_union>::value);
+    ASSERT_FALSE(zll::meta::is_union<test_struct>::value);
+    ASSERT_FALSE(zll::meta::is_union<int>::value);
+}