1 
2 //  (C) Copyright John Maddock 2015.
3 //  Use, modification and distribution are subject to the Boost Software License,
4 //  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
5 //  http://www.boost.org/LICENSE_1_0.txt).
6 //
7 //  See http://www.boost.org/libs/type_traits for most recent version including documentation.
8 
9 #ifndef BOOST_TT_IS_CONSTRUCTIBLE_HPP_INCLUDED
10 #define BOOST_TT_IS_CONSTRUCTIBLE_HPP_INCLUDED
11 
12 #include <boost/type_traits/integral_constant.hpp>
13 #include <boost/detail/workaround.hpp>
14 
15 #if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && !defined(BOOST_NO_CXX11_DECLTYPE) && !BOOST_WORKAROUND(BOOST_MSVC, < 1800) && !BOOST_WORKAROUND(BOOST_GCC_VERSION, < 40500)
16 
17 #include <boost/type_traits/is_destructible.hpp>
18 #include <boost/type_traits/is_default_constructible.hpp>
19 #include <boost/type_traits/detail/yes_no_type.hpp>
20 #include <boost/type_traits/declval.hpp>
21 
22 namespace boost{
23 
24    namespace detail{
25 
26       struct is_constructible_imp
27       {
28          template<typename T, typename ...TheArgs, typename = decltype(T(boost::declval<TheArgs>()...))>
29          static boost::type_traits::yes_type test(int);
30          template<typename, typename...>
31          static boost::type_traits::no_type test(...);
32 
33          template<typename T, typename Arg, typename = decltype(::new T(boost::declval<Arg>()))>
34          static boost::type_traits::yes_type test1(int);
35          template<typename, typename>
36          static boost::type_traits::no_type test1(...);
37 
38          template <typename T>
39          static boost::type_traits::yes_type ref_test(T);
40          template <typename T>
41          static boost::type_traits::no_type ref_test(...);
42       };
43 
44    }
45 
46    template <class T, class ...Args> struct is_constructible : public integral_constant<bool, sizeof(detail::is_constructible_imp::test<T, Args...>(0)) == sizeof(boost::type_traits::yes_type)>{};
47    template <class T, class Arg> struct is_constructible<T, Arg> : public integral_constant<bool, is_destructible<T>::value && sizeof(detail::is_constructible_imp::test1<T, Arg>(0)) == sizeof(boost::type_traits::yes_type)>{};
48    template <class Ref, class Arg> struct is_constructible<Ref&, Arg> : public integral_constant<bool, sizeof(detail::is_constructible_imp::ref_test<Ref&>(boost::declval<Arg>())) == sizeof(boost::type_traits::yes_type)>{};
49    template <class Ref, class Arg> struct is_constructible<Ref&&, Arg> : public integral_constant<bool, sizeof(detail::is_constructible_imp::ref_test<Ref&&>(boost::declval<Arg>())) == sizeof(boost::type_traits::yes_type)>{};
50 
51    template <> struct is_constructible<void> : public false_type{};
52    template <> struct is_constructible<void const> : public false_type{};
53    template <> struct is_constructible<void const volatile> : public false_type{};
54    template <> struct is_constructible<void volatile> : public false_type{};
55 
56    template <class T> struct is_constructible<T> : public is_default_constructible<T>{};
57 
58 #else
59 
60 #include <boost/type_traits/is_convertible.hpp>
61 #include <boost/type_traits/is_default_constructible.hpp>
62 
63 namespace boost{
64 
65    // We don't know how to implement this:
66    template <class T, class U = void> struct is_constructible : public is_convertible<U, T>{};
67    template <class T> struct is_constructible<T, void> : public is_default_constructible<T>{};
68    template <> struct is_constructible<void, void> : public false_type{};
69    template <> struct is_constructible<void const, void> : public false_type{};
70    template <> struct is_constructible<void const volatile, void> : public false_type{};
71    template <> struct is_constructible<void volatile, void> : public false_type{};
72    template <class Ref> struct is_constructible<Ref&, void> : public false_type{};
73 #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
74    template <class Ref> struct is_constructible<Ref&&, void> : public false_type{};
75 #endif
76 #endif
77 
78 } // namespace boost
79 
80 #endif // BOOST_TT_IS_CONSTRUCTIBLE_HPP_INCLUDED
81