Fix: prevented the binding illegal temporary to optional<const int&>

Older MSVC versions add illegal temporary when you want to assign from const integral value.

test/Jamfile.v2

@@ -39,6 +39,7 @@ import testing ;
     [ run optional_test_emplace.cpp ]
     [ run optional_test_minimum_requirements.cpp ]
     [ run optional_test_msvc_bug_workaround.cpp ]
+    [ compile-fail optional_test_ref_convert_assign_const_int_prevented.cpp ]
     [ compile-fail optional_test_fail1.cpp ]
     [ compile-fail optional_test_fail3a.cpp ]
     [ compile-fail optional_test_fail3b.cpp ]

test/optional_ref_assign_test_defs.hpp

@@ -163,26 +163,11 @@ void test_rebinding_assignment_semantics()
   BOOST_TEST_EQ(val(v), 2);
 }
 
-template <typename T>
+template <typename T, typename U>
 void test_converting_assignment()
 {
   typename concrete_type_of<T>::type v1(1), v2(2), v3(3);
-  optional<T&> oA(v1), oB(none);
-  
-  oA = v2;
-  BOOST_TEST(oA);
-  BOOST_TEST(addressof(*oA) == addressof(v2));
-  
-  oB = v3;
-  BOOST_TEST(oB);
-  BOOST_TEST(addressof(*oB) == addressof(v3));
-}
-
-template <typename T>
-void test_converting_assignment_for_noconst_const()
-{
-  typename concrete_type_of<T>::type v1(1), v2(2), v3(3);
-  optional<const T&> oA(v1), oB(none);
+  optional<U&> oA(v1), oB(none);
   
   oA = v2;
   BOOST_TEST(oA);
@@ -194,4 +179,3 @@ void test_converting_assignment_for_noconst_const()
 }
 
 #endif //BOOST_OPTIONAL_TEST_OPTIONAL_REF_ASSIGN_TEST_DEFS_AK_07JAN2015_HPP
-

test/optional_test_ref_convert_assign_const_int.cpp

@@ -23,8 +23,8 @@
 
 int main()
 {
-  test_converting_assignment<const int>();
-  test_converting_assignment_for_noconst_const<int>();
-  
+#ifndef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT
+  test_converting_assignment<const int, const int>();
+#endif
   return boost::report_errors();
 }

test/optional_test_ref_convert_assign_const_int_prevented.cpp

@@ -0,0 +1,32 @@
+// Copyright (C) 2015 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is 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/lib/optional for documentation.
+//
+// You are welcome to contact the author at: akrzemi1@gmail.com
+
+
+#include "boost/optional/optional.hpp"
+
+#ifdef __BORLANDC__
+#pragma hdrstop
+#endif
+
+#include "boost/core/addressof.hpp"
+#include "boost/core/enable_if.hpp"
+#include "boost/core/lightweight_test.hpp"
+#include "testable_classes.hpp"
+#include "optional_ref_assign_test_defs.hpp"
+
+int main()
+{
+#ifdef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT
+  test_converting_assignment<const int, const int>();
+#else
+  BOOST_STATIC_ASSERT(false, "EXPECTED TEST COMPILE-TIME FAILURE");
+#endif
+  return boost::report_errors();
+}

test/optional_test_ref_convert_assign_mutable_int.cpp

@@ -23,7 +23,8 @@
 
 int main()
 {
-  test_converting_assignment<int>();
+  test_converting_assignment<int, int>();
+  test_converting_assignment<int, const int>();
   
   return boost::report_errors();
 }

test/optional_test_ref_convert_assign_non_int.cpp

@@ -25,9 +25,9 @@
 template <typename T>
 void test_all_const_cases()
 {
-  test_converting_assignment<T>();
-  test_converting_assignment<const T>();
-  test_converting_assignment_for_noconst_const<T>();
+  test_converting_assignment<T, T>();
+  test_converting_assignment<const T, const T>();
+  test_converting_assignment<T, const T>();
 }
 
 int main()