From acf6e41edbcacf2cdc45311cdd29267a3a94b373 Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Sat, 6 Jun 2015 12:51:51 +0100
Subject: [PATCH] Add is_assignable. Update has_nothrow_assign to make use of
 it.

---
 include/boost/type_traits.hpp                 |   2 +
 .../boost/type_traits/has_nothrow_assign.hpp  |  29 ++--
 include/boost/type_traits/intrinsics.hpp      |   2 +-
 include/boost/type_traits/is_assignable.hpp   |  76 +++++++++
 test/has_nothrow_assign_test.cpp              |  27 ++++
 test/is_assignable_test.cpp                   | 151 ++++++++++++++++++
 6 files changed, 275 insertions(+), 12 deletions(-)
 create mode 100644 include/boost/type_traits/is_assignable.hpp
 create mode 100644 test/is_assignable_test.cpp

diff --git a/include/boost/type_traits.hpp b/include/boost/type_traits.hpp
index 4c9d8eb..cf35c68 100644
--- a/include/boost/type_traits.hpp
+++ b/include/boost/type_traits.hpp
@@ -41,6 +41,7 @@
 #include "boost/type_traits/has_trivial_move_constructor.hpp"
 #include "boost/type_traits/has_virtual_destructor.hpp"
 #include "boost/type_traits/is_abstract.hpp"
+#include "boost/type_traits/is_assignable.hpp"
 #include "boost/type_traits/is_arithmetic.hpp"
 #include "boost/type_traits/is_array.hpp"
 #include "boost/type_traits/is_base_and_derived.hpp"
@@ -52,6 +53,7 @@
 #include "boost/type_traits/is_convertible.hpp"
 #include "boost/type_traits/is_copy_constructible.hpp"
 #include "boost/type_traits/is_copy_assignable.hpp"
+#include "boost/type_traits/is_default_constructible.hpp"
 #include "boost/type_traits/is_empty.hpp"
 #include "boost/type_traits/is_enum.hpp"
 #include "boost/type_traits/is_float.hpp"
diff --git a/include/boost/type_traits/has_nothrow_assign.hpp b/include/boost/type_traits/has_nothrow_assign.hpp
index c337fd6..c864eef 100644
--- a/include/boost/type_traits/has_nothrow_assign.hpp
+++ b/include/boost/type_traits/has_nothrow_assign.hpp
@@ -19,11 +19,14 @@
 #include <boost/type_traits/is_const.hpp>
 #include <boost/type_traits/is_volatile.hpp>
 #include <boost/type_traits/is_reference.hpp>
+#include <boost/type_traits/is_assignable.hpp>
+#include <boost/type_traits/add_reference.hpp>
 #endif
 #endif
 #if defined(__GNUC__) || defined(__SUNPRO_CC)
 #include <boost/type_traits/is_const.hpp>
 #include <boost/type_traits/is_volatile.hpp>
+#include <boost/type_traits/is_assignable.hpp>
 #ifdef BOOST_INTEL
 #include <boost/type_traits/is_pod.hpp>
 #endif
@@ -35,28 +38,32 @@ namespace boost {
 
    namespace detail
    {
-      template <class T, bool b1> struct has_nothrow_assign_imp{ static const bool value = false; };
-      template <class T>          struct has_nothrow_assign_imp<T, false>{ static const bool value = noexcept(detail::tt_decl_ref<T>() = detail::tt_decl_const_ref<T>()); };
-      template <class T, std::size_t N> struct has_nothrow_assign_imp<T[N], false>{ static const bool value = has_nothrow_assign_imp<T, false>::value; };
-      template <class T>          struct has_nothrow_assign_imp<T[], false>{ static const bool value = has_nothrow_assign_imp<T, false>::value; };
+      template <class T, bool b1, bool b2> struct has_nothrow_assign_imp{ static const bool value = false; };
+      template <class T>          struct has_nothrow_assign_imp<T, false, true>{ static const bool value = noexcept(detail::tt_decl_ref<T>() = detail::tt_decl_const_ref<T>()); };
+      template <class T, std::size_t N> struct has_nothrow_assign_imp<T[N], false, true>{ static const bool value = has_nothrow_assign_imp<T, false, true>::value; };
+      template <class T>          struct has_nothrow_assign_imp<T[], false, true>{ static const bool value = has_nothrow_assign_imp<T, false, true>::value; };
    }
 
 #endif
 
-template <class T>
-struct has_nothrow_assign : public integral_constant<bool,
+   template <class T>
+   struct has_nothrow_assign : public integral_constant < bool,
 #ifndef BOOST_HAS_NOTHROW_ASSIGN
 #if !defined(BOOST_NO_CXX11_NOEXCEPT) && !defined(BOOST_NO_SFINAE_EXPR) && !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
-   // Portable C++11 version:
-   detail::has_nothrow_assign_imp<T, is_const<typename remove_reference<T>::type>::value || is_volatile<typename remove_reference<T>::type>::value || is_reference<T>::value>::value
+      // Portable C++11 version:
+      detail::has_nothrow_assign_imp<T, 
+      (is_const<typename remove_reference<T>::type>::value || is_volatile<typename remove_reference<T>::type>::value || is_reference<T>::value), 
+      is_assignable<typename add_reference<T>::type, typename add_reference<const T>::type>::value
+      >::value
 #else
-   ::boost::has_trivial_assign<T>::value
+      ::boost::has_trivial_assign<T>::value
 #endif
 #else
-   BOOST_HAS_NOTHROW_ASSIGN(T)
+      BOOST_HAS_NOTHROW_ASSIGN(T)
 #endif
->{};
+   > {};
 
+template <class T, std::size_t N> struct has_nothrow_assign <T[N]> : public has_nothrow_assign<T> {};
 template <> struct has_nothrow_assign<void> : public false_type{};
 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
 template <> struct has_nothrow_assign<void const> : public false_type{};
diff --git a/include/boost/type_traits/intrinsics.hpp b/include/boost/type_traits/intrinsics.hpp
index 1d66176..2d85f8b 100644
--- a/include/boost/type_traits/intrinsics.hpp
+++ b/include/boost/type_traits/intrinsics.hpp
@@ -245,7 +245,7 @@
 #   define BOOST_HAS_TRIVIAL_DESTRUCTOR(T) (__has_trivial_destructor(T) BOOST_INTEL_TT_OPTS)
 #   define BOOST_HAS_NOTHROW_CONSTRUCTOR(T) (__has_nothrow_constructor(T) && is_default_constructible<T>::value BOOST_INTEL_TT_OPTS)
 #   define BOOST_HAS_NOTHROW_COPY(T) ((__has_nothrow_copy(T) BOOST_INTEL_TT_OPTS) && !is_volatile<T>::value && !is_reference<T>::value)
-#   define BOOST_HAS_NOTHROW_ASSIGN(T) ((__has_nothrow_assign(T) BOOST_INTEL_TT_OPTS) && !is_volatile<T>::value && !is_const<T>::value)
+#   define BOOST_HAS_NOTHROW_ASSIGN(T) ((__has_nothrow_assign(T) BOOST_INTEL_TT_OPTS) && !is_volatile<T>::value && !is_const<T>::value && is_assignable<T&, const T&>::value)
 #   define BOOST_HAS_VIRTUAL_DESTRUCTOR(T) __has_virtual_destructor(T)
 
 #   define BOOST_IS_ABSTRACT(T) __is_abstract(T)
diff --git a/include/boost/type_traits/is_assignable.hpp b/include/boost/type_traits/is_assignable.hpp
new file mode 100644
index 0000000..1095f80
--- /dev/null
+++ b/include/boost/type_traits/is_assignable.hpp
@@ -0,0 +1,76 @@
+
+//  (C) Copyright John Maddock 2015.
+//  Use, modification and distribution are subject to the Boost Software License,
+//  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt).
+//
+//  See http://www.boost.org/libs/type_traits for most recent version including documentation.
+
+#ifndef BOOST_TT_IS_ASSIGNABLE_HPP_INCLUDED
+#define BOOST_TT_IS_ASSIGNABLE_HPP_INCLUDED
+
+#include <boost/type_traits/integral_constant.hpp>
+#include <boost/detail/workaround.hpp>
+
+namespace boost{
+
+   template <class T, class U = T> struct is_assignable;
+
+}
+
+#if !defined(BOOST_NO_CXX11_DECLTYPE) && !BOOST_WORKAROUND(BOOST_MSVC, < 1800)
+
+#include <boost/type_traits/detail/yes_no_type.hpp>
+#include <boost/type_traits/detail/decl.hpp>
+
+namespace boost{
+
+   namespace detail{
+
+      struct is_assignable_imp
+      {
+         template<typename T, typename U, typename = decltype(tt_declval<T>() = tt_declval<U>())>
+         static boost::type_traits::yes_type test(int);
+
+         template<typename, typename>
+         static boost::type_traits::no_type test(...);
+      };
+
+   }
+
+   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)>{};
+   template <class T, std::size_t N, class U> struct is_assignable<T[N], U> : public is_assignable<T, U>{};
+   template <class T, std::size_t N, class U> struct is_assignable<T(&)[N], U> : public is_assignable<T&, U>{};
+   template <class T, class U> struct is_assignable<T[], U> : public is_assignable<T, U>{};
+   template <class T, class U> struct is_assignable<T(&)[], U> : public is_assignable<T&, U>{};
+   template <class U> struct is_assignable<void, U> : public integral_constant<bool, false>{};
+   template <class U> struct is_assignable<void const, U> : public integral_constant<bool, false>{};
+   template <class U> struct is_assignable<void volatile, U> : public integral_constant<bool, false>{};
+   template <class U> struct is_assignable<void const volatile, U> : public integral_constant<bool, false>{};
+
+#else
+
+#include <boost/type_traits/has_trivial_assign.hpp>
+#include <boost/type_traits/remove_reference.hpp>
+
+namespace boost{
+
+   // We don't know how to implement this:
+   template <class T, class U> struct is_assignable : public integral_constant<bool, false>{};
+   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>{};
+   template <class T, class U> struct is_assignable<const T&, U> : public integral_constant<bool, false>{};
+   template <class U> struct is_assignable<void, U> : public integral_constant<bool, false>{};
+   template <class U> struct is_assignable<void const, U> : public integral_constant<bool, false>{};
+   template <class U> struct is_assignable<void volatile, U> : public integral_constant<bool, false>{};
+   template <class U> struct is_assignable<void const volatile, U> : public integral_constant<bool, false>{};
+   /*
+   template <> struct is_assignable<void, void> : public integral_constant<bool, false>{};
+   template <> struct is_assignable<void const, void const> : public integral_constant<bool, false>{};
+   template <> struct is_assignable<void volatile, void volatile> : public integral_constant<bool, false>{};
+   template <> struct is_assignable<void const volatile, void const volatile> : public integral_constant<bool, false>{};
+   */
+#endif
+
+} // namespace boost
+
+#endif // BOOST_TT_IS_ASSIGNABLE_HPP_INCLUDED
diff --git a/test/has_nothrow_assign_test.cpp b/test/has_nothrow_assign_test.cpp
index ec3d110..ee221ee 100644
--- a/test/has_nothrow_assign_test.cpp
+++ b/test/has_nothrow_assign_test.cpp
@@ -12,6 +12,26 @@
 #  include <boost/type_traits/has_nothrow_assign.hpp>
 #endif
 
+#ifndef BOOST_NO_CXX11_DELETED_FUNCTIONS
+
+struct non_assignable
+{
+   non_assignable();
+   non_assignable& operator=(const non_assignable&) = delete;
+};
+
+#endif
+
+#ifndef BOOST_NO_CXX11_NOEXCEPT
+
+struct noexcept_assignable
+{
+   noexcept_assignable();
+   noexcept_assignable& operator=(const non_assignable&)noexcept;
+};
+
+#endif
+
 TT_TEST_BEGIN(has_nothrow_assign)
 
 BOOST_CHECK_INTEGRAL_CONSTANT(::tt::has_nothrow_assign<bool>::value, true);
@@ -205,6 +225,13 @@ BOOST_CHECK_INTEGRAL_CONSTANT(::tt::has_nothrow_assign<nothrow_construct_UDT>::v
 
 BOOST_CHECK_INTEGRAL_CONSTANT(::tt::has_nothrow_assign<test_abc1>::value, false);
 
+#ifndef BOOST_NO_CXX11_DELETED_FUNCTIONS
+BOOST_CHECK_INTEGRAL_CONSTANT(::tt::has_nothrow_assign<non_assignable>::value, false);
+#endif
+#ifndef BOOST_NO_CXX11_NOEXCEPT
+BOOST_CHECK_INTEGRAL_CONSTANT(::tt::has_nothrow_assign<noexcept_assignable>::value, true);
+#endif
+
 TT_TEST_END
 
 
diff --git a/test/is_assignable_test.cpp b/test/is_assignable_test.cpp
new file mode 100644
index 0000000..8a13ca2
--- /dev/null
+++ b/test/is_assignable_test.cpp
@@ -0,0 +1,151 @@
+
+//  (C) Copyright John Maddock 2000. 
+//  Use, modification and distribution are subject to the 
+//  Boost Software License, Version 1.0. (See accompanying file 
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include "test.hpp"
+#include "check_integral_constant.hpp"
+#ifdef TEST_STD
+#  include <type_traits>
+#else
+#  include <boost/type_traits/is_assignable.hpp>
+#endif
+
+#ifndef BOOST_NO_CXX11_DELETED_FUNCTIONS
+
+struct non_assignable
+{
+   non_assignable();
+   non_assignable& operator=(const non_assignable&) = delete;
+};
+
+#endif
+
+#ifndef BOOST_NO_CXX11_NOEXCEPT
+
+struct noexcept_assignable
+{
+   noexcept_assignable();
+   noexcept_assignable& operator=(const non_assignable&)noexcept;
+};
+
+#endif
+
+TT_TEST_BEGIN(is_assignable)
+
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<bool&, const bool&>::value), true);
+#ifndef TEST_STD
+// unspecified behaviour:
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<bool const&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<bool volatile&, bool const volatile&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<bool const volatile&>::value), false);
+#endif
+
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<signed char&, const signed char&>::value), true);
+#ifndef TEST_STD
+// unspecified behaviour:
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<signed char const&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<signed char volatile&, const signed char volatile&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<signed char const volatile&>::value), false);
+#endif
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<unsigned char&, const unsigned char&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<char&, const char&>::value), true);
+
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<unsigned short&, const unsigned short&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<short&, const short&>::value), true);
+
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<unsigned int&, const unsigned int&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<int&, const int&>::value), true);
+#ifndef TEST_STD
+// unspecified behaviour:
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<unsigned int const&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<int const&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<unsigned int volatile&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<int volatile&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<unsigned int const volatile&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<int const volatile&>::value), false);
+#endif
+
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<unsigned long&, const unsigned long&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<long&, const long&>::value), true);
+#ifndef TEST_STD
+// unspecified behaviour:
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<unsigned long const&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<long const&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<unsigned long volatile&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<long volatile&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<unsigned long const volatile&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<long const volatile&>::value), false);
+#endif
+
+#ifdef BOOST_HAS_LONG_LONG
+
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable< ::boost::ulong_long_type&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable< ::boost::long_long_type&>::value), true);
+#ifndef TEST_STD
+// unspecified behaviour:
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable< ::boost::ulong_long_type const&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable< ::boost::long_long_type const&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable< ::boost::ulong_long_type volatile&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable< ::boost::long_long_type volatile&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable< ::boost::ulong_long_type const volatile&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable< ::boost::long_long_type const volatile&>::value), false);
+#endif
+#endif
+
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<float&, const float&>::value), true);
+#ifndef TEST_STD
+// unspecified behaviour:
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<float const&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<float volatile&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<float const volatile&>::value), false);
+#endif
+
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<double&, const double&>::value), true);
+#ifndef TEST_STD
+// unspecified behaviour:
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<double const&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<double volatile&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<double const volatile&>::value), false);
+#endif
+
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<long double&, const long double&>::value), true);
+#ifndef TEST_STD
+// unspecified behaviour:
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<long double const&>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<long double volatile&>::value), true);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<long double const volatile&>::value), false);
+#endif
+
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<void*&>::value), true);
+#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<int&, int&&>::value), true);
+#endif
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<const int&>::value), false);
+//BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<int(&)[2], const int(&)[2]>::value), true);
+//BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<int(&)[3][2]>::value), true);
+//BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<int(&)[2][4][5][6][3]>::value), true);
+BOOST_CHECK_SOFT_INTEGRAL_CONSTANT((::tt::is_assignable<UDT&>::value), true, false);
+BOOST_CHECK_SOFT_INTEGRAL_CONSTANT((::tt::is_assignable<empty_UDT&>::value), true, false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<void>::value), false);
+// cases we would like to succeed but can't implement in the language:
+BOOST_CHECK_SOFT_INTEGRAL_CONSTANT((::tt::is_assignable<empty_POD_UDT&>::value), true, false);
+BOOST_CHECK_SOFT_INTEGRAL_CONSTANT((::tt::is_assignable<POD_UDT&>::value), true, false);
+BOOST_CHECK_SOFT_INTEGRAL_CONSTANT((::tt::is_assignable<POD_union_UDT&>::value), true, false);
+BOOST_CHECK_SOFT_INTEGRAL_CONSTANT((::tt::is_assignable<empty_POD_union_UDT&>::value), true, false);
+BOOST_CHECK_SOFT_INTEGRAL_CONSTANT((::tt::is_assignable<nothrow_assign_UDT&>::value), true, false);
+
+BOOST_CHECK_SOFT_INTEGRAL_CONSTANT((::tt::is_assignable<test_abc1&>::value), true, false);
+
+#ifndef BOOST_NO_CXX11_DELETED_FUNCTIONS
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<non_assignable&>::value), false);
+#endif
+#ifndef BOOST_NO_CXX11_NOEXCEPT
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_assignable<noexcept_assignable&>::value), true);
+#endif
+
+TT_TEST_END
+
+
+