boost/type_traits/is_constructible.hpp

0001
0002 //  (C) Copyright John Maddock 2015.
0003 //  Use, modification and distribution are subject to the Boost Software License,
0004 //  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
0005 //  http://www.boost.org/LICENSE_1_0.txt).
0006 //
0007 //  See http://www.boost.org/libs/type_traits for most recent version including documentation.
0008
0009 #ifndef BOOST_TT_IS_CONSTRUCTIBLE_HPP_INCLUDED
0010 #define BOOST_TT_IS_CONSTRUCTIBLE_HPP_INCLUDED
0011
0012 #include <boost/type_traits/integral_constant.hpp>
0013 #include <boost/detail/workaround.hpp>
0014
0015 #if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && !defined(BOOST_NO_CXX11_DECLTYPE) && !BOOST_WORKAROUND(BOOST_MSVC, < 1800) && !BOOST_WORKAROUND(BOOST_GCC_VERSION, < 40500)
0016
0017 #include <boost/type_traits/is_destructible.hpp>
0018 #include <boost/type_traits/is_default_constructible.hpp>
0019 #include <boost/type_traits/detail/yes_no_type.hpp>
0020 #include <boost/type_traits/declval.hpp>
0021 #include <boost/type_traits/is_complete.hpp>
0022 #include <boost/static_assert.hpp>
0023
0024 #define BOOST_TT_IS_CONSTRUCTIBLE_CONFORMING 1
0025
0026 namespace boost{
0027
0028    namespace detail{
0029
0030       struct is_constructible_imp
0031       {
0032          template<typename T, typename ...TheArgs, typename = decltype(T(boost::declval<TheArgs>()...))>
0033          static boost::type_traits::yes_type test(int);
0034          template<typename, typename...>
0035          static boost::type_traits::no_type test(...);
0036
0037          template<typename T, typename Arg, typename = decltype(::new T(boost::declval<Arg>()))>
0038          static boost::type_traits::yes_type test1(int);
0039          template<typename, typename>
0040          static boost::type_traits::no_type test1(...);
0041
0042          template <typename T>
0043          static boost::type_traits::yes_type ref_test(T);
0044          template <typename T>
0045          static boost::type_traits::no_type ref_test(...);
0046       };
0047
0048    }
0049
0050    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)>
0051    {
0052       BOOST_STATIC_ASSERT_MSG(::boost::is_complete<T>::value, "The target type must be complete in order to test for constructibility");
0053    };
0054    template <class T, class Arg> struct is_constructible<T, Arg> : public integral_constant<bool, is_destructible<T>::value && sizeof(boost::detail::is_constructible_imp::test1<T, Arg>(0)) == sizeof(boost::type_traits::yes_type)>
0055    {
0056       BOOST_STATIC_ASSERT_MSG(::boost::is_complete<T>::value, "The target type must be complete in order to test for constructibility");
0057    };
0058    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)>{};
0059    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)>{};
0060
0061    template <> struct is_constructible<void> : public false_type{};
0062    template <> struct is_constructible<void const> : public false_type{};
0063    template <> struct is_constructible<void const volatile> : public false_type{};
0064    template <> struct is_constructible<void volatile> : public false_type{};
0065
0066    template <class T> struct is_constructible<T> : public is_default_constructible<T>{};
0067
0068 #else
0069
0070 #include <boost/type_traits/is_convertible.hpp>
0071 #include <boost/type_traits/is_default_constructible.hpp>
0072
0073 namespace boost{
0074
0075    // We don't know how to implement this:
0076    template <class T, class U = void> struct is_constructible : public is_convertible<U, T>{};
0077    template <class T> struct is_constructible<T, void> : public is_default_constructible<T>{};
0078    template <> struct is_constructible<void, void> : public false_type{};
0079    template <> struct is_constructible<void const, void> : public false_type{};
0080    template <> struct is_constructible<void const volatile, void> : public false_type{};
0081    template <> struct is_constructible<void volatile, void> : public false_type{};
0082    template <class Ref> struct is_constructible<Ref&, void> : public false_type{};
0083 #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
0084    template <class Ref> struct is_constructible<Ref&&, void> : public false_type{};
0085 #endif
0086 #endif
0087
0088 } // namespace boost
0089
0090 #endif // BOOST_TT_IS_CONSTRUCTIBLE_HPP_INCLUDED