1 /*=============================================================================
2     Copyright (c) 2015 Kohei Takahashi
3 
4     Use modification and distribution are subject to the Boost Software
5     License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
6     http://www.boost.org/LICENSE_1_0.txt).
7 ==============================================================================*/
8 
9 #ifndef FUSION_TEST_SFINAE_FRIENDLY_HPP
10 #define FUSION_TEST_SFINAE_FRIENDLY_HPP
11 
12 #include <boost/config.hpp>
13 #include <boost/mpl/bool.hpp>
14 #include <boost/mpl/assert.hpp>
15 #include <boost/utility/result_of.hpp>
16 #include <boost/core/enable_if.hpp>
17 
18 #if !defined(BOOST_NO_SFINAE) && defined(BOOST_RESULT_OF_USE_DECLTYPE)
19 
20 #include <boost/fusion/container/vector.hpp>
21 
22 namespace sfinae_friendly
23 {
24     template <typename> struct arg_;
25     template <typename R, typename T> struct arg_<R(T)> { typedef T type; };
26 
27     template <typename Traits, typename = void>
28     struct check
29         : boost::mpl::true_ { };
30 
31     template <typename Traits>
32     struct check<Traits, typename boost::enable_if_has_type<typename Traits::type>::type>
33         : boost::mpl::false_ { };
34 
35     struct unspecified {};
36     typedef boost::fusion::vector<> v0;
37     typedef boost::fusion::vector<unspecified> v1;
38     typedef boost::fusion::vector<unspecified, unspecified> v2;
39     typedef boost::fusion::vector<unspecified, unspecified, unspecified> v3;
40 }
41 
42 #define SFINAE_FRIENDLY_ASSERT(Traits) \
43     BOOST_MPL_ASSERT((::sfinae_friendly::check<typename ::sfinae_friendly::arg_<void Traits>::type>))
44 
45 #else
46 
47 #define SFINAE_FRIENDLY_ASSERT(Traits) \
48     BOOST_MPL_ASSERT((boost::mpl::true_))
49 
50 #endif
51 
52 #endif // FUSION_TEST_SFINAE_FRIENDLY_HPP
53 
54