Add BOOST_DESCRIBE_NESTED_ENUM

include/boost/describe/enum.hpp

@@ -10,6 +10,7 @@
 #if !defined(BOOST_DESCRIBE_CXX14)
 
 #define BOOST_DESCRIBE_ENUM(E, ...)
+#define BOOST_DESCRIBE_NESTED_ENUM(E, ...)
 
 #else
 
@@ -60,6 +61,12 @@ template<class... T> auto enum_descriptor_fn_impl( int, T... )
     BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_ENUM_ENTRY, E, __VA_ARGS__) \
     BOOST_DESCRIBE_ENUM_END(E)
 
+#define BOOST_DESCRIBE_NESTED_ENUM(E, ...) \
+    static_assert(std::is_enum<E>::value, "BOOST_DESCRIBE_NESTED_ENUM should only be used with enums"); \
+    friend BOOST_DESCRIBE_ENUM_BEGIN(E) \
+    BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_ENUM_ENTRY, E, __VA_ARGS__) \
+    BOOST_DESCRIBE_ENUM_END(E)
+
 #else
 
 #define BOOST_DESCRIBE_ENUM(E, ...) \
@@ -68,6 +75,12 @@ template<class... T> auto enum_descriptor_fn_impl( int, T... )
     BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_ENUM_ENTRY, E, ##__VA_ARGS__) \
     BOOST_DESCRIBE_ENUM_END(E)
 
+#define BOOST_DESCRIBE_NESTED_ENUM(E, ...) \
+    static_assert(std::is_enum<E>::value, "BOOST_DESCRIBE_NESTED_ENUM should only be used with enums"); \
+    friend BOOST_DESCRIBE_ENUM_BEGIN(E) \
+    BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_ENUM_ENTRY, E, ##__VA_ARGS__) \
+    BOOST_DESCRIBE_ENUM_END(E)
+
 #endif
 
 } // namespace describe

test/Jamfile

@@ -25,6 +25,7 @@ run pp_pointer_test.cpp ;
 run enumerators_test.cpp ;
 run empty_enum_test.cpp ;
 run trailing_comma_test.cpp ;
+run nested_enum_test.cpp ;
 
 run compute_base_modifiers.cpp ;
 run bases_test.cpp ;

test/nested_enum_test.cpp

@@ -0,0 +1,130 @@
+// Copyright 2020, 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/describe/enumerators.hpp>
+#include <boost/describe/enum.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+struct X1
+{
+    enum E
+    {
+        v1 = 5
+    };
+
+    BOOST_DESCRIBE_NESTED_ENUM(E, v1)
+};
+
+class X2
+{
+private:
+
+    enum E
+    {
+        v1, v2
+    };
+
+    BOOST_DESCRIBE_NESTED_ENUM(E, v1, v2)
+
+public:
+
+    typedef E E2;
+};
+
+#if !defined(BOOST_DESCRIBE_CXX11)
+
+#include <boost/config/pragma_message.hpp>
+
+BOOST_PRAGMA_MESSAGE("Skipping test because C++11 is not available")
+int main() {}
+
+#else
+
+struct X3
+{
+    enum class E
+    {
+        v1 = 7
+    };
+
+    BOOST_DESCRIBE_NESTED_ENUM(E, v1)
+};
+
+class X4
+{
+private:
+
+    enum class E
+    {
+        v1, v2
+    };
+
+    BOOST_DESCRIBE_NESTED_ENUM(E, v1, v2)
+
+public:
+
+    typedef E E2;
+};
+
+#if !defined(BOOST_DESCRIBE_CXX14)
+
+#include <boost/config/pragma_message.hpp>
+
+BOOST_PRAGMA_MESSAGE("Skipping test because C++14 is not available")
+int main() {}
+
+#else
+
+#include <boost/mp11.hpp>
+using namespace boost::mp11;
+
+int main()
+{
+    {
+        using D = boost::describe::describe_enumerators<X1::E>;
+
+        BOOST_TEST_EQ( mp_size<D>::value, 1 );
+
+        BOOST_TEST_EQ( (mp_at_c<D, 0>::value), X1::v1 );
+        BOOST_TEST_CSTR_EQ( (mp_at_c<D, 0>::name), "v1" );
+    }
+
+    {
+        using D = boost::describe::describe_enumerators<X2::E2>;
+
+        BOOST_TEST_EQ( mp_size<D>::value, 2 );
+
+        BOOST_TEST_EQ( (mp_at_c<D, 0>::value), 0 );
+        BOOST_TEST_CSTR_EQ( (mp_at_c<D, 0>::name), "v1" );
+
+        BOOST_TEST_EQ( (mp_at_c<D, 1>::value), 1 );
+        BOOST_TEST_CSTR_EQ( (mp_at_c<D, 1>::name), "v2" );
+    }
+
+    {
+        using D = boost::describe::describe_enumerators<X3::E>;
+
+        BOOST_TEST_EQ( mp_size<D>::value, 1 );
+
+        BOOST_TEST_EQ( (int)(mp_at_c<D, 0>::value), (int)X3::E::v1 );
+        BOOST_TEST_CSTR_EQ( (mp_at_c<D, 0>::name), "v1" );
+    }
+
+    {
+        using D = boost::describe::describe_enumerators<X4::E2>;
+
+        BOOST_TEST_EQ( mp_size<D>::value, 2 );
+
+        BOOST_TEST_EQ( (int)(mp_at_c<D, 0>::value), 0 );
+        BOOST_TEST_CSTR_EQ( (mp_at_c<D, 0>::name), "v1" );
+
+        BOOST_TEST_EQ( (int)(mp_at_c<D, 1>::value), 1 );
+        BOOST_TEST_CSTR_EQ( (mp_at_c<D, 1>::name), "v2" );
+    }
+
+    return boost::report_errors();
+}
+
+#endif // !defined(BOOST_DESCRIBE_CXX14)
+#endif // !defined(BOOST_DESCRIBE_CXX11)