From 2429f259cc58d09d01d51d27082c8c59551eb9b3 Mon Sep 17 00:00:00 2001
From: Antony Polukhin <antoshkka@gmail.com>
Date: Mon, 22 Jul 2013 12:51:09 +0000
Subject: [PATCH] Unify behavior of is_copy_constructible triat when dealing
 with rvalues + add comments for some tests (refs #8802):

[SVN r85104]
---
 .../type_traits/is_copy_constructible.hpp     |  9 ++++++---
 test/is_copy_constructible_test.cpp           | 20 +++++++++++++++++--
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/include/boost/type_traits/is_copy_constructible.hpp b/include/boost/type_traits/is_copy_constructible.hpp
index 032ad2b..4e87131 100644
--- a/include/boost/type_traits/is_copy_constructible.hpp
+++ b/include/boost/type_traits/is_copy_constructible.hpp
@@ -13,6 +13,7 @@
 #include <boost/type_traits/detail/yes_no_type.hpp>
 #include <boost/type_traits/is_base_and_derived.hpp>
 #include <boost/type_traits/add_reference.hpp>
+#include <boost/type_traits/is_rvalue_reference.hpp>
 #include <boost/utility/declval.hpp>
 #include <boost/noncopyable.hpp>
 
@@ -67,9 +68,11 @@ struct is_copy_constructible_impl2 {
     //          ...
     //      };
     BOOST_STATIC_CONSTANT(bool, value = (
-        sizeof(test(
-            boost::declval<BOOST_DEDUCED_TYPENAME boost::add_reference<T>::type>()
-        )) == sizeof(boost::type_traits::yes_type)
+            sizeof(test(
+                boost::declval<BOOST_DEDUCED_TYPENAME boost::add_reference<T>::type>()
+            )) == sizeof(boost::type_traits::yes_type)
+        ||
+            boost::is_rvalue_reference<T>::value
     ));
 };
 
diff --git a/test/is_copy_constructible_test.cpp b/test/is_copy_constructible_test.cpp
index 7cca73a..0ab0a9f 100644
--- a/test/is_copy_constructible_test.cpp
+++ b/test/is_copy_constructible_test.cpp
@@ -259,11 +259,27 @@ BOOST_CHECK_INTEGRAL_CONSTANT(::tt::is_copy_constructible<enum_UDT>::value, true
 
 BOOST_CHECK_INTEGRAL_CONSTANT(::tt::is_copy_constructible<int&>::value, true);
 #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
-BOOST_CHECK_INTEGRAL_CONSTANT(::tt::is_copy_constructible<int&&>::value, false);
+// Code like `int&& a = 10;` or 
+//      struct nonc {
+//          nonc() = default;
+//          nonc(const nonc&) = delete;
+//          nonc(nonc&&) = delete;
+//          nonc& operator=(const nonc&) = delete;
+//          nonc& operator=(nonc&&) = delete;
+//      };
+//
+//      nonc && a = nonc();
+// is legal in C++11. so this trait MUST return true.
+BOOST_CHECK_INTEGRAL_CONSTANT(::tt::is_copy_constructible<int&&>::value, true);
 #endif
 BOOST_CHECK_INTEGRAL_CONSTANT(::tt::is_copy_constructible<const int&>::value, true);
 
-// Following three tests may give different results because of copiler and C++03/C++11
+
+// Following three tests may give different results because of compiler and C++03/C++11.
+// On C++11 compiler following code:
+//      int c[2][4][5][6][3];
+//      int b[2][4][5][6][3] = std::move(c);
+// does not compile, so we expect `false` to be the result of those three tests.
 BOOST_CHECK_SOFT_INTEGRAL_CONSTANT(::tt::is_copy_constructible<int[2]>::value, false, true);
 BOOST_CHECK_SOFT_INTEGRAL_CONSTANT(::tt::is_copy_constructible<int[3][2]>::value, false, true);
 BOOST_CHECK_SOFT_INTEGRAL_CONSTANT(::tt::is_copy_constructible<int[2][4][5][6][3]>::value, false, true);