1// (C) Copyright Ion Gaztanaga 2014.
2//
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_COPY_ASSIGNABLE_HPP_INCLUDED
10#define BOOST_TT_IS_COPY_ASSIGNABLE_HPP_INCLUDED
11
12#include <boost/config.hpp>
13#include <boost/type_traits/detail/yes_no_type.hpp>
14#include <boost/type_traits/is_noncopyable.hpp>
15
16#if !defined(BOOST_NO_CXX11_DELETED_FUNCTIONS) && !defined(BOOST_NO_CXX11_DECLTYPE) \
17 && !defined(BOOST_INTEL_CXX_VERSION) && \
18 !(defined(BOOST_MSVC) && _MSC_VER == 1800)
19#define BOOST_TT_CXX11_IS_COPY_ASSIGNABLE
20#include <boost/type_traits/declval.hpp>
21#else
22 //For compilers without decltype
23 #include <boost/type_traits/is_const.hpp>
24 #include <boost/type_traits/is_array.hpp>
25 #include <boost/type_traits/add_reference.hpp>
26 #include <boost/type_traits/remove_reference.hpp>
27#endif
28
29namespace boost {
30
31namespace detail{
32
33template <bool DerivedFromNoncopyable, class T>
34struct is_copy_assignable_impl2 {
35
36// Intel compiler has problems with SFINAE for copy constructors and deleted functions:
37//
38// error: function *function_name* cannot be referenced -- it is a deleted function
39// static boost::type_traits::yes_type test(T1&, decltype(T1(boost::declval<T1&>()))* = 0);
40// ^
41//
42// MSVC 12.0 (Visual 2013) has problems when the copy constructor has been deleted. See:
43// https://connect.microsoft.com/VisualStudio/feedback/details/800328/std-is-copy-constructible-is-broken
44#if defined(BOOST_TT_CXX11_IS_COPY_ASSIGNABLE)
45 typedef boost::type_traits::yes_type yes_type;
46 typedef boost::type_traits::no_type no_type;
47
48 template <class U>
49 static decltype(::boost::declval<U&>() = ::boost::declval<const U&>(), yes_type() ) test(int);
50
51 template <class>
52 static no_type test(...);
53
54 static const bool value = sizeof(test<T>(0)) == sizeof(yes_type);
55
56#else
57 static BOOST_DEDUCED_TYPENAME boost::add_reference<T>::type produce();
58
59 template <class T1>
60 static boost::type_traits::no_type test(T1&, typename T1::boost_move_no_copy_constructor_or_assign* = 0);
61
62 static boost::type_traits::yes_type test(...);
63 // If you see errors like this:
64 //
65 // `'T::operator=(const T&)' is private`
66 // `boost/type_traits/is_copy_assignable.hpp:NN:M: error: within this context`
67 //
68 // then you are trying to call that macro for a structure defined like that:
69 //
70 // struct T {
71 // ...
72 // private:
73 // T & operator=(const T &);
74 // ...
75 // };
76 //
77 // To fix that you must modify your structure:
78 //
79 // // C++03 and C++11 version
80 // struct T: private boost::noncopyable {
81 // ...
82 // private:
83 // T & operator=(const T &);
84 // ...
85 // };
86 //
87 // // C++11 version
88 // struct T {
89 // ...
90 // private:
91 // T& operator=(const T &) = delete;
92 // ...
93 // };
94 BOOST_STATIC_CONSTANT(bool, value = (
95 sizeof(test(produce())) == sizeof(boost::type_traits::yes_type)
96 ));
97 #endif
98};
99
100template <class T>
101struct is_copy_assignable_impl2<true, T> {
102 BOOST_STATIC_CONSTANT(bool, value = false);
103};
104
105template <class T>
106struct is_copy_assignable_impl {
107
108#if !defined(BOOST_TT_CXX11_IS_COPY_ASSIGNABLE)
109 //For compilers without decltype, at least return false on const types, arrays
110 //types derived from boost::noncopyable and types defined as BOOST_MOVEABLE_BUT_NOT_COPYABLE
111 typedef BOOST_DEDUCED_TYPENAME boost::remove_reference<T>::type unreferenced_t;
112 BOOST_STATIC_CONSTANT(bool, value = (
113 boost::detail::is_copy_assignable_impl2<
114 boost::is_noncopyable<T>::value
115 || boost::is_const<unreferenced_t>::value || boost::is_array<unreferenced_t>::value
116 ,T
117 >::value
118 ));
119 #else
120 BOOST_STATIC_CONSTANT(bool, value = (
121 boost::detail::is_copy_assignable_impl2<
122 boost::is_noncopyable<T>::value,T
123 >::value
124 ));
125 #endif
126};
127
128} // namespace detail
129
130template <class T> struct is_copy_assignable : public integral_constant<bool, ::boost::detail::is_copy_assignable_impl<T>::value>{};
131template <> struct is_copy_assignable<void> : public false_type{};
132#ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
133template <> struct is_copy_assignable<void const> : public false_type{};
134template <> struct is_copy_assignable<void const volatile> : public false_type{};
135template <> struct is_copy_assignable<void volatile> : public false_type{};
136#endif
137
138} // namespace boost
139
140#endif // BOOST_TT_IS_COPY_ASSIGNABLE_HPP_INCLUDED
141

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