member tester macros

Author: atkurtul

include/nbl/builtin/hlsl/member_test_macros.hlsl

@@ -0,0 +1,50 @@
+// Copyright (C) 2022 - DevSH Graphics Programming Sp. z O.O.
+// This file is part of the "Nabla Engine".
+// For conditions of distribution and use, see copyright notice in nabla.h
+#ifndef _NBL_BUILTIN_HLSL_MEMBER_TEST_MACROS_INCLUDED_
+#define _NBL_BUILTIN_HLSL_MEMBER_TEST_MACROS_INCLUDED_
+
+#include <nbl/builtin/hlsl/type_traits.hlsl>
+
+#ifdef __HLSL_VERSION
+#define NBL_GENERATE_MEMBER_TESTER(mem) \
+namespace nbl\
+{\
+namespace hlsl\
+{\
+    template<class T, class=bool_constant<true> > \
+    struct has_member_##mem : false_type {}; \
+    template<class T> \
+    struct has_member_##mem<T,bool_constant<impl::valid_expression<decltype(impl::declval<T>().mem)>::value> > : true_type {}; \
+}\
+}
+
+namespace nbl
+{
+namespace hlsl
+{
+
+namespace impl
+{
+
+template<class T>
+struct valid_expression : true_type {};
+
+template<> struct valid_expression<void> : false_type {};
+
+template<class T>
+T declval(){}
+
+}
+
+}
+
+}
+
+NBL_GENERATE_MEMBER_TESTER(x)
+NBL_GENERATE_MEMBER_TESTER(y)
+NBL_GENERATE_MEMBER_TESTER(z)
+NBL_GENERATE_MEMBER_TESTER(w)
+
+#endif
+#endif

include/nbl/builtin/hlsl/type_traits.hlsl

@@ -487,6 +487,9 @@ using integral_constant = std::integral_constant<T, val>;
 template<bool val>
 using bool_constant = std::bool_constant<val>;
 
+using bool_constant = std::true_type;
+using false_type    = std::false_type;
+
 template <bool C, class T, class F>
 using conditional  = std::conditional<C, T, F>;