Extracted BOOST_EXPLICIT_OPERATOR_BOOL macro from Boost.Log.

[SVN r85543]

test/explicit_operator_bool.cpp

@@ -0,0 +1,54 @@
+/*
+ *          Copyright Andrey Semashev 2007 - 2013.
+ * Distributed under 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)
+ */
+/*!
+ * \file   explicit_operator_bool_compile.cpp
+ * \author Andrey Semashev
+ * \date   17.07.2010
+ *
+ * \brief  This test checks that explicit operator bool can be used in
+ *         the valid contexts.
+ */
+
+#define BOOST_TEST_MODULE explicit_operator_bool_compile
+
+#include <boost/utility/explicit_operator_bool.hpp>
+
+namespace {
+
+    // A test object that has the operator of explicit conversion to bool
+    struct checkable1
+    {
+        BOOST_EXPLICIT_OPERATOR_BOOL()
+        bool operator! () const
+        {
+            return false;
+        }
+    };
+
+    struct checkable2
+    {
+        BOOST_CONSTEXPR_EXPLICIT_OPERATOR_BOOL()
+        BOOST_CONSTEXPR bool operator! () const
+        {
+            return false;
+        }
+    };
+
+} // namespace
+
+int main(int, char*[])
+{
+    checkable1 val1;
+    if (val1)
+    {
+        checkable2 val2;
+        if (val2)
+            return 0;
+    }
+
+    return 1;
+}