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_base_and_derived.hpp>
15#include <boost/noncopyable.hpp>
16
17#if !defined(BOOST_NO_CXX11_DELETED_FUNCTIONS) && !defined(BOOST_NO_CXX11_DECLTYPE) \
18 && !defined(BOOST_INTEL_CXX_VERSION) && \
19 !(defined(BOOST_MSVC) && _MSC_VER == 1800)
20#define BOOST_TT_CXX11_IS_COPY_ASSIGNABLE
21#include <boost/type_traits/declval.hpp>
22#else
23 //For compilers without decltype
24 #include <boost/type_traits/is_const.hpp>
25 #include <boost/type_traits/is_array.hpp>
26 #include <boost/type_traits/add_reference.hpp>
27 #include <boost/type_traits/remove_reference.hpp>
28#endif
29
30namespace boost {
31
32namespace detail{
33
34template <bool DerivedFromNoncopyable, class T>
35struct is_copy_assignable_impl2 {
36
37// Intel compiler has problems with SFINAE for copy constructors and deleted functions:
38//
39// error: function *function_name* cannot be referenced -- it is a deleted function
40// static boost::type_traits::yes_type test(T1&, decltype(T1(boost::declval<T1&>()))* = 0);
41// ^
42//
43// MSVC 12.0 (Visual 2013) has problems when the copy constructor has been deleted. See:
44// https://connect.microsoft.com/VisualStudio/feedback/details/800328/std-is-copy-constructible-is-broken
45#if defined(BOOST_TT_CXX11_IS_COPY_ASSIGNABLE)
46 typedef boost::type_traits::yes_type yes_type;
47 typedef boost::type_traits::no_type no_type;
48
49 template <class U>
50 static decltype(::boost::declval<U&>() = ::boost::declval<const U&>(), yes_type() ) test(int);
51
52 template <class>
53 static no_type test(...);
54
55 static const bool value = sizeof(test<T>(0)) == sizeof(yes_type);
56
57#else
58 static BOOST_DEDUCED_TYPENAME boost::add_reference<T>::type produce();
59
60 template <class T1>
61 static boost::type_traits::no_type test(T1&, typename T1::boost_move_no_copy_constructor_or_assign* = 0);
62
63 static boost::type_traits::yes_type test(...);
64 // If you see errors like this:
65 //
66 // `'T::operator=(const T&)' is private`
67 // `boost/type_traits/is_copy_assignable.hpp:NN:M: error: within this context`
68 //
69 // then you are trying to call that macro for a structure defined like that:
70 //
71 // struct T {
72 // ...
73 // private:
74 // T & operator=(const T &);
75 // ...
76 // };
77 //
78 // To fix that you must modify your structure:
79 //
80 // // C++03 and C++11 version
81 // struct T: private boost::noncopyable {
82 // ...
83 // private:
84 // T & operator=(const T &);
85 // ...
86 // };
87 //
88 // // C++11 version
89 // struct T {
90 // ...
91 // private:
92 // T& operator=(const T &) = delete;
93 // ...
94 // };
95 BOOST_STATIC_CONSTANT(bool, value = (
96 sizeof(test(produce())) == sizeof(boost::type_traits::yes_type)
97 ));
98 #endif
99};
100
101template <class T>
102struct is_copy_assignable_impl2<true, T> {
103 BOOST_STATIC_CONSTANT(bool, value = false);
104};
105
106template <class T>
107struct is_copy_assignable_impl {
108
109#if !defined(BOOST_TT_CXX11_IS_COPY_ASSIGNABLE)
110 //For compilers without decltype, at least return false on const types, arrays
111 //types derived from boost::noncopyable and types defined as BOOST_MOVEABLE_BUT_NOT_COPYABLE
112 typedef BOOST_DEDUCED_TYPENAME boost::remove_reference<T>::type unreferenced_t;
113 BOOST_STATIC_CONSTANT(bool, value = (
114 boost::detail::is_copy_assignable_impl2<
115 boost::is_base_and_derived<boost::noncopyable, T>::value
116 || boost::is_const<unreferenced_t>::value || boost::is_array<unreferenced_t>::value
117 ,T
118 >::value
119 ));
120 #else
121 BOOST_STATIC_CONSTANT(bool, value = (
122 boost::detail::is_copy_assignable_impl2<
123 boost::is_base_and_derived<boost::noncopyable, T>::value,T
124 >::value
125 ));
126 #endif
127};
128
129} // namespace detail
130
131template <class T> struct is_copy_assignable : public integral_constant<bool, ::boost::detail::is_copy_assignable_impl<T>::value>{};
132template <> struct is_copy_assignable<void> : public false_type{};
133#ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
134template <> struct is_copy_assignable<void const> : public false_type{};
135template <> struct is_copy_assignable<void const volatile> : public false_type{};
136template <> struct is_copy_assignable<void volatile> : public false_type{};
137#endif
138
139} // namespace boost
140
141#endif // BOOST_TT_IS_COPY_ASSIGNABLE_HPP_INCLUDED
142

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