Use NBL_VALID_EXPRESSION, always_true is NOT a way to check the validity of an expression!

Author: devsh

include/nbl/builtin/hlsl/cpp_compat/impl/intrinsics_impl.hlsl

@@ -42,9 +42,9 @@ inline bool isinf_uint_impl(UnsignedInteger val)
 namespace impl
 {
 #ifndef __HLSL_VERSION
-template<typename T, typename U>
-NBL_BOOL_CONCEPT MixIsCallable = always_true<decltype(glm::mix(declval<T>(), declval<T>(), declval<U>()))>;
+NBL_VALID_EXPRESSION(MixIsCallable, (T)(U), glm::mix(declval<T>(),declval<T>(),declval<U>()));
 #endif
+
 template<typename T, typename U>
 NBL_BOOL_CONCEPT MixCallingBuiltins =
 #ifdef __HLSL_VERSION

include/nbl/builtin/hlsl/spirv_intrinsics/glsl.std.450.hlsl

@@ -95,8 +95,7 @@ template<typename T NBL_FUNC_REQUIRES(concepts::FloatingPointVectorOrScalar<T>)
 [[vk::ext_instruction(GLSLstd450::GLSLstd450FMix, "GLSL.std.450")]]
 T fMix(T x, T y, T a);
 
-template<typename T>
-NBL_BOOL_CONCEPT FMixIsCallable = always_true<decltype(spirv::fMix<T>(experimental::declval<T>(), experimental::declval<T>(), experimental::declval<T>()))>;
+NBL_VALID_EXPRESSION(FMixIsCallable, (T), spirv::fMix<T>(experimental::declval<T>(),experimental::declval<T>(),experimental::declval<T>()));
 
 template<typename SquareMatrix NBL_FUNC_REQUIRES(matrix_traits<SquareMatrix>::Square)
 [[vk::ext_instruction(GLSLstd450::GLSLstd450Determinant, "GLSL.std.450")]]