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_ASSIGNABLE_HPP_INCLUDED
10#define BOOST_TT_IS_ASSIGNABLE_HPP_INCLUDED
11
12#include <boost/type_traits/integral_constant.hpp>
13#include <boost/detail/workaround.hpp>
14
15namespace boost{
16
17 template <class T, class U = T> struct is_assignable;
18
19}
20
21#if !defined(BOOST_NO_CXX11_DECLTYPE) && !BOOST_WORKAROUND(BOOST_MSVC, < 1800)
22
23#include <boost/type_traits/detail/yes_no_type.hpp>
24#include <boost/type_traits/declval.hpp>
25
26namespace boost{
27
28 namespace detail{
29
30 struct is_assignable_imp
31 {
32 template<typename T, typename U, typename = decltype(boost::declval<T>() = boost::declval<U>())>
33 static boost::type_traits::yes_type test(int);
34
35 template<typename, typename>
36 static boost::type_traits::no_type test(...);
37 };
38
39 }
40
41 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)>{};
42 template <class T, std::size_t N, class U> struct is_assignable<T[N], U> : public is_assignable<T, U>{};
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, class U> struct is_assignable<T[], 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 U> struct is_assignable<void, U> : public integral_constant<bool, false>{};
47 template <class U> struct is_assignable<void const, U> : public integral_constant<bool, false>{};
48 template <class U> struct is_assignable<void volatile, U> : public integral_constant<bool, false>{};
49 template <class U> struct is_assignable<void const volatile, U> : public integral_constant<bool, false>{};
50
51#else
52
53#include <boost/type_traits/has_trivial_assign.hpp>
54#include <boost/type_traits/remove_reference.hpp>
55
56namespace boost{
57
58 // We don't know how to implement this:
59 template <class T, class U> struct is_assignable : public integral_constant<bool, false>{};
60 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>{};
61 template <class T, class U> struct is_assignable<const T&, U> : public integral_constant<bool, false>{};
62 template <class U> struct is_assignable<void, U> : public integral_constant<bool, false>{};
63 template <class U> struct is_assignable<void const, U> : public integral_constant<bool, false>{};
64 template <class U> struct is_assignable<void volatile, U> : public integral_constant<bool, false>{};
65 template <class U> struct is_assignable<void const volatile, U> : public integral_constant<bool, false>{};
66 /*
67 template <> struct is_assignable<void, void> : public integral_constant<bool, false>{};
68 template <> struct is_assignable<void const, void const> : public integral_constant<bool, false>{};
69 template <> struct is_assignable<void volatile, void volatile> : public integral_constant<bool, false>{};
70 template <> struct is_assignable<void const volatile, void const volatile> : public integral_constant<bool, false>{};
71 */
72#endif
73
74} // namespace boost
75
76#endif // BOOST_TT_IS_ASSIGNABLE_HPP_INCLUDED
77