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
22namespace 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
63namespace 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

source code of boost/boost/type_traits/is_constructible.hpp