From 0171246a618f558934d48c392083513f2e995987 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Fri, 28 Oct 2022 01:47:27 +0300
Subject: [PATCH] Add is_described_class<T>

---
 .../container_hash/is_described_class.hpp     | 35 ++++++++++++
 test/Jamfile.v2                               |  5 ++
 test/is_described_class_test.cpp              | 56 +++++++++++++++++++
 test/is_described_class_test2.cpp             | 35 ++++++++++++
 4 files changed, 131 insertions(+)
 create mode 100644 include/boost/container_hash/is_described_class.hpp
 create mode 100644 test/is_described_class_test.cpp
 create mode 100644 test/is_described_class_test2.cpp

diff --git a/include/boost/container_hash/is_described_class.hpp b/include/boost/container_hash/is_described_class.hpp
new file mode 100644
index 0000000..81f16d5
--- /dev/null
+++ b/include/boost/container_hash/is_described_class.hpp
@@ -0,0 +1,35 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#ifndef BOOST_HASH_IS_DESCRIBED_CLASS_HPP_INCLUDED
+#define BOOST_HASH_IS_DESCRIBED_CLASS_HPP_INCLUDED
+
+#include <boost/type_traits/integral_constant.hpp>
+#include <boost/describe/bases.hpp>
+#include <boost/describe/members.hpp>
+
+namespace boost
+{
+namespace container_hash
+{
+
+#if defined(BOOST_DESCRIBE_CXX11)
+
+template<class T> struct is_described_class: boost::integral_constant<bool,
+    describe::has_describe_bases<T>::value && describe::has_describe_members<T>::value>
+{
+};
+
+#else
+
+template<class T> struct is_described_class: boost::false_type
+{
+};
+
+#endif
+
+} // namespace container_hash
+} // namespace boost
+
+#endif // #ifndef BOOST_HASH_IS_DESCRIBED_CLASS_HPP_INCLUDED
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index e72f200..647f6dc 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -102,3 +102,8 @@ run is_range_test3.cpp ;
 run is_contiguous_range_test2.cpp ;
 run is_unordered_range_test2.cpp ;
 run is_contiguous_range_test3.cpp ;
+
+run is_described_class_test.cpp
+  : : : <warnings>extra ;
+run is_described_class_test2.cpp
+  : : : <warnings>extra ;
diff --git a/test/is_described_class_test.cpp b/test/is_described_class_test.cpp
new file mode 100644
index 0000000..66516ff
--- /dev/null
+++ b/test/is_described_class_test.cpp
@@ -0,0 +1,56 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/container_hash/is_described_class.hpp>
+#include <boost/describe/class.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <string>
+
+struct X1
+{
+};
+
+struct X2
+{
+    int m;
+};
+
+struct Y1
+{
+};
+
+BOOST_DESCRIBE_STRUCT( Y1, (), () )
+
+struct Y2: Y1
+{
+    int m;
+};
+
+BOOST_DESCRIBE_STRUCT( Y2, (Y1), (m) )
+
+int main()
+{
+    using boost::container_hash::is_described_class;
+
+    BOOST_TEST_TRAIT_FALSE((is_described_class<void>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<int>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<X1>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<X2>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<int[2]>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<std::string>));
+
+#if defined(BOOST_DESCRIBE_CXX14)
+
+    BOOST_TEST_TRAIT_TRUE((is_described_class<Y1>));
+    BOOST_TEST_TRAIT_TRUE((is_described_class<Y2>));
+
+#else
+
+    BOOST_TEST_TRAIT_FALSE((is_described_class<Y1>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<Y2>));
+
+#endif
+
+    return boost::report_errors();
+}
diff --git a/test/is_described_class_test2.cpp b/test/is_described_class_test2.cpp
new file mode 100644
index 0000000..70a0d8d
--- /dev/null
+++ b/test/is_described_class_test2.cpp
@@ -0,0 +1,35 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/type_traits/integral_constant.hpp>
+#include <boost/describe/class.hpp>
+
+struct X
+{
+};
+
+BOOST_DESCRIBE_STRUCT( X, (), () )
+
+namespace boost
+{
+namespace container_hash
+{
+
+template<class T> struct is_described_class;
+template<> struct is_described_class<X>: boost::false_type {};
+
+} // namespace container_hash
+} // namespace boost
+
+#include <boost/container_hash/is_described_class.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+
+int main()
+{
+    using boost::container_hash::is_described_class;
+
+    BOOST_TEST_TRAIT_FALSE((is_described_class<X>));
+
+    return boost::report_errors();
+}