boost/type_traits/is_copy_assignable.hpp

   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/utility/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
  30
  31 // should be the last #include
  32 #include <boost/type_traits/detail/bool_trait_def.hpp>
  33
  34 namespace boost {
  35
  36 namespace detail{
  37
  38 template <bool DerivedFromNoncopyable, class T>
  39 struct is_copy_assignable_impl2 {
  40
  41 // Intel compiler has problems with SFINAE for copy constructors and deleted functions:
  42 //
  43 // error: function *function_name* cannot be referenced -- it is a deleted function
  44 // static boost::type_traits::yes_type test(T1&, decltype(T1(boost::declval<T1&>()))* = 0);
  45 //                                                        ^
  46 //
  47 // MSVC 12.0 (Visual 2013) has problems when the copy constructor has been deleted. See:
  48 // https://connect.microsoft.com/VisualStudio/feedback/details/800328/std-is-copy-constructible-is-broken
  49 #if defined(BOOST_TT_CXX11_IS_COPY_ASSIGNABLE)
  50     typedef boost::type_traits::yes_type yes_type;
  51     typedef boost::type_traits::no_type  no_type;
  52
  53     template <class U>
  54     static decltype(::boost::declval<U&>() = ::boost::declval<const U&>(), yes_type() ) test(int);
  55
  56     template <class>
  57     static no_type test(...);
  58
  59     static const bool value = sizeof(test<T>(0)) == sizeof(yes_type);
  60
  61 #else
  62     static BOOST_DEDUCED_TYPENAME boost::add_reference<T>::type produce();
  63
  64     template <class T1>
  65     static boost::type_traits::no_type test(T1&, typename T1::boost_move_no_copy_constructor_or_assign* = 0);
  66
  67     static boost::type_traits::yes_type test(...);
  68     // If you see errors like this:
  69     //
  70     //      `'T::operator=(const T&)' is private`
  71     //      `boost/type_traits/is_copy_assignable.hpp:NN:M: error: within this context`
  72     //
  73     // then you are trying to call that macro for a structure defined like that:
  74     //
  75     //      struct T {
  76     //          ...
  77     //      private:
  78     //          T & operator=(const T &);
  79     //          ...
  80     //      };
  81     //
  82     // To fix that you must modify your structure:
  83     //
  84     //      // C++03 and C++11 version
  85     //      struct T: private boost::noncopyable {
  86     //          ...
  87     //      private:
  88     //          T & operator=(const T &);
  89     //          ...
  90     //      };
  91     //
  92     //      // C++11 version
  93     //      struct T {
  94     //          ...
  95     //      private:
  96     //          T& operator=(const T &) = delete;
  97     //          ...
  98     //      };
  99     BOOST_STATIC_CONSTANT(bool, value = (
 100             sizeof(test(produce())) == sizeof(boost::type_traits::yes_type)
 101     ));
 102    #endif
 103 };
 104
 105 template <class T>
 106 struct is_copy_assignable_impl2<true, T> {
 107     BOOST_STATIC_CONSTANT(bool, value = false);
 108 };
 109
 110 template <class T>
 111 struct is_copy_assignable_impl {
 112
 113 #if !defined(BOOST_TT_CXX11_IS_COPY_ASSIGNABLE)
 114     //For compilers without decltype, at least return false on const types, arrays
 115     //types derived from boost::noncopyable and types defined as BOOST_MOVEABLE_BUT_NOT_COPYABLE
 116     typedef BOOST_DEDUCED_TYPENAME boost::remove_reference<T>::type unreferenced_t;
 117     BOOST_STATIC_CONSTANT(bool, value = (
 118         boost::detail::is_copy_assignable_impl2<
 119             boost::is_base_and_derived<boost::noncopyable, T>::value
 120             || boost::is_const<unreferenced_t>::value || boost::is_array<unreferenced_t>::value
 121             ,T
 122         >::value
 123     ));
 124     #else
 125     BOOST_STATIC_CONSTANT(bool, value = (
 126         boost::detail::is_copy_assignable_impl2<
 127             boost::is_base_and_derived<boost::noncopyable, T>::value,T
 128         >::value
 129     ));
 130     #endif
 131 };
 132
 133 } // namespace detail
 134
 135 BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_copy_assignable,T,::boost::detail::is_copy_assignable_impl<T>::value)
 136 BOOST_TT_AUX_BOOL_TRAIT_SPEC1(is_copy_assignable,void,false)
 137 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
 138 BOOST_TT_AUX_BOOL_TRAIT_SPEC1(is_copy_assignable,void const,false)
 139 BOOST_TT_AUX_BOOL_TRAIT_SPEC1(is_copy_assignable,void const volatile,false)
 140 BOOST_TT_AUX_BOOL_TRAIT_SPEC1(is_copy_assignable,void volatile,false)
 141 #endif
 142
 143 } // namespace boost
 144
 145 #include <boost/type_traits/detail/bool_trait_undef.hpp>
 146
 147 #endif // BOOST_TT_IS_COPY_ASSIGNABLE_HPP_INCLUDED