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 <cstddef> // size_t
13#include <boost/type_traits/integral_constant.hpp>
14#include <boost/detail/workaround.hpp>
15#include <boost/type_traits/is_complete.hpp>
16#include <boost/static_assert.hpp>
17
18namespace boost{
19
20 template <class T, class U = T> struct is_assignable;
21
22}
23
24#if !defined(BOOST_NO_CXX11_DECLTYPE) && !BOOST_WORKAROUND(BOOST_MSVC, < 1800)
25
26#include <boost/type_traits/detail/yes_no_type.hpp>
27#include <boost/type_traits/declval.hpp>
28
29namespace boost{
30
31 namespace detail{
32
33 struct is_assignable_imp
34 {
35 template<typename T, typename U, typename = decltype(boost::declval<T>() = boost::declval<U>())>
36 static boost::type_traits::yes_type test(int);
37
38 template<typename, typename>
39 static boost::type_traits::no_type test(...);
40 };
41
42 }
43
44 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)>
45 {
46 BOOST_STATIC_ASSERT_MSG(boost::is_complete<T>::value, "Arguments to is_assignable must be complete types");
47 };
48 template <class T, std::size_t N, class U> struct is_assignable<T[N], U> : public is_assignable<T, U>{};
49 template <class T, std::size_t N, class U> struct is_assignable<T(&)[N], U> : public is_assignable<T&, U>{};
50 template <class T, class U> struct is_assignable<T[], U> : public is_assignable<T, U>{};
51 template <class T, class U> struct is_assignable<T(&)[], U> : public is_assignable<T&, U>{};
52 template <class U> struct is_assignable<void, U> : public integral_constant<bool, false>{};
53 template <class U> struct is_assignable<void const, U> : public integral_constant<bool, false>{};
54 template <class U> struct is_assignable<void volatile, U> : public integral_constant<bool, false>{};
55 template <class U> struct is_assignable<void const volatile, U> : public integral_constant<bool, false>{};
56
57#else
58
59#include <boost/type_traits/has_trivial_assign.hpp>
60#include <boost/type_traits/remove_reference.hpp>
61
62namespace boost{
63
64 // We don't know how to implement this:
65 template <class T, class U> struct is_assignable : public integral_constant<bool, false>
66 {
67 BOOST_STATIC_ASSERT_MSG(boost::is_complete<T>::value, "Arguments to is_assignable must be complete types");
68 };
69 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>{};
70 template <class T, class U> struct is_assignable<const T&, U> : public integral_constant<bool, false>{};
71 template <class U> struct is_assignable<void, U> : public integral_constant<bool, false>{};
72 template <class U> struct is_assignable<void const, U> : public integral_constant<bool, false>{};
73 template <class U> struct is_assignable<void volatile, U> : public integral_constant<bool, false>{};
74 template <class U> struct is_assignable<void const volatile, U> : public integral_constant<bool, false>{};
75 /*
76 template <> struct is_assignable<void, void> : public integral_constant<bool, false>{};
77 template <> struct is_assignable<void const, void const> : public integral_constant<bool, false>{};
78 template <> struct is_assignable<void volatile, void volatile> : public integral_constant<bool, false>{};
79 template <> struct is_assignable<void const volatile, void const volatile> : public integral_constant<bool, false>{};
80 */
81#endif
82
83} // namespace boost
84
85#endif // BOOST_TT_IS_ASSIGNABLE_HPP_INCLUDED
86

source code of include/boost/type_traits/is_assignable.hpp