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).
7 // See http://www.boost.org/libs/type_traits for most recent version including documentation.
9 #ifndef BOOST_TT_IS_ASSIGNABLE_HPP_INCLUDED
10 #define BOOST_TT_IS_ASSIGNABLE_HPP_INCLUDED
12 #include <cstddef> // size_t
13 #include <boost/type_traits/integral_constant.hpp>
14 #include <boost/detail/workaround.hpp>
18 template <class T, class U = T> struct is_assignable;
22 #if !defined(BOOST_NO_CXX11_DECLTYPE) && !BOOST_WORKAROUND(BOOST_MSVC, < 1800)
24 #include <boost/type_traits/detail/yes_no_type.hpp>
25 #include <boost/type_traits/declval.hpp>
31 struct is_assignable_imp
33 template<typename T, typename U, typename = decltype(boost::declval<T>() = boost::declval<U>())>
34 static boost::type_traits::yes_type test(int);
36 template<typename, typename>
37 static boost::type_traits::no_type test(...);
42 template <class T, class U> struct is_assignable : public integral_constant<bool, sizeof(detail::is_assignable_imp::test<T, U>(0)) == sizeof(boost::type_traits::yes_type)>{};
43 template <class T, std::size_t N, class U> struct is_assignable<T[N], U> : public is_assignable<T, U>{};
44 template <class T, std::size_t N, class U> struct is_assignable<T(&)[N], U> : public is_assignable<T&, U>{};
45 template <class T, class U> struct is_assignable<T[], U> : public is_assignable<T, U>{};
46 template <class T, class U> struct is_assignable<T(&)[], U> : public is_assignable<T&, U>{};
47 template <class U> struct is_assignable<void, U> : public integral_constant<bool, false>{};
48 template <class U> struct is_assignable<void const, U> : public integral_constant<bool, false>{};
49 template <class U> struct is_assignable<void volatile, U> : public integral_constant<bool, false>{};
50 template <class U> struct is_assignable<void const volatile, U> : public integral_constant<bool, false>{};
54 #include <boost/type_traits/has_trivial_assign.hpp>
55 #include <boost/type_traits/remove_reference.hpp>
59 // We don't know how to implement this:
60 template <class T, class U> struct is_assignable : public integral_constant<bool, false>{};
61 template <class T, class U> struct is_assignable<T&, U> : public integral_constant<bool, is_pod<T>::value && is_pod<typename remove_reference<U>::type>::value>{};
62 template <class T, class U> struct is_assignable<const T&, U> : public integral_constant<bool, false>{};
63 template <class U> struct is_assignable<void, U> : public integral_constant<bool, false>{};
64 template <class U> struct is_assignable<void const, U> : public integral_constant<bool, false>{};
65 template <class U> struct is_assignable<void volatile, U> : public integral_constant<bool, false>{};
66 template <class U> struct is_assignable<void const volatile, U> : public integral_constant<bool, false>{};
68 template <> struct is_assignable<void, void> : public integral_constant<bool, false>{};
69 template <> struct is_assignable<void const, void const> : public integral_constant<bool, false>{};
70 template <> struct is_assignable<void volatile, void volatile> : public integral_constant<bool, false>{};
71 template <> struct is_assignable<void const volatile, void const volatile> : public integral_constant<bool, false>{};
77 #endif // BOOST_TT_IS_ASSIGNABLE_HPP_INCLUDED