Document has_*

.github/workflows/ci.yml

@@ -19,18 +19,15 @@ jobs:
         include:
           - toolset: gcc-4.8
             cxxstd: "03,11"
-            os: ubuntu-16.04
+            os: ubuntu-18.04
             install: g++-4.8
-          - toolset: gcc-4.9
-            cxxstd: "03,11"
-            os: ubuntu-16.04
-            install: g++-4.9
           - toolset: gcc-5
             cxxstd: "03,11,14,14-gnu,1z,1z-gnu"
-            os: ubuntu-16.04
+            os: ubuntu-18.04
+            install: g++-5
           - toolset: gcc-6
             cxxstd: "03,11,14,14-gnu,1z,1z-gnu"
-            os: ubuntu-16.04
+            os: ubuntu-18.04
             install: g++-6
           - toolset: gcc-7
             cxxstd: "03,11,14,14-gnu,17,17-gnu"
@@ -38,51 +35,38 @@ jobs:
           - toolset: gcc-8
             cxxstd: "03,11,14,17,2a"
             os: ubuntu-18.04
+            install: g++-8
           - toolset: gcc-9
             cxxstd: "03,11,14,17,2a"
-            os: ubuntu-18.04
+            os: ubuntu-20.04
           - toolset: gcc-10
             cxxstd: "03,11,14,17,2a"
-            os: ubuntu-18.04
-          - toolset: clang
-            compiler: clang++-3.5
-            cxxstd: "03,11,14"
-            os: ubuntu-16.04
-            install: clang-3.5
-          - toolset: clang
-            compiler: clang++-3.6
-            cxxstd: "03,11,14"
-            os: ubuntu-16.04
-            install: clang-3.6
-          - toolset: clang
-            compiler: clang++-3.7
-            cxxstd: "03,11,14"
-            os: ubuntu-16.04
-            install: clang-3.7
-          - toolset: clang
-            compiler: clang++-3.8
-            cxxstd: "03,11,14"
-            os: ubuntu-16.04
-            install: clang-3.8
+            os: ubuntu-20.04
+            install: g++-10
+          - toolset: gcc-11
+            cxxstd: "03,11,14,17,2a"
+            os: ubuntu-20.04
+            install: g++-11
           - toolset: clang
             compiler: clang++-3.9
             cxxstd: "03,11,14"
-            os: ubuntu-16.04
+            os: ubuntu-18.04
             install: clang-3.9
           - toolset: clang
             compiler: clang++-4.0
             cxxstd: "03,11,14"
-            os: ubuntu-16.04
+            os: ubuntu-18.04
             install: clang-4.0
           - toolset: clang
             compiler: clang++-5.0
             cxxstd: "03,11,14,1z"
-            os: ubuntu-16.04
+            os: ubuntu-18.04
             install: clang-5.0
           - toolset: clang
             compiler: clang++-6.0
             cxxstd: "03,11,14,17"
             os: ubuntu-18.04
+            install: clang-6.0
           - toolset: clang
             compiler: clang++-7
             cxxstd: "03,11,14,17"
@@ -90,16 +74,29 @@ jobs:
             install: clang-7
           - toolset: clang
             compiler: clang++-8
-            cxxstd: "03,11,14,17,2a"
+            cxxstd: "03,11,14,17"
             os: ubuntu-20.04
+            install: clang-8
           - toolset: clang
             compiler: clang++-9
             cxxstd: "03,11,14,17,2a"
             os: ubuntu-20.04
+            install: clang-9
           - toolset: clang
             compiler: clang++-10
             cxxstd: "03,11,14,17,2a"
             os: ubuntu-20.04
+            install: clang-10
+          - toolset: clang
+            compiler: clang++-11
+            cxxstd: "03,11,14,17,2a"
+            os: ubuntu-20.04
+            install: clang-11
+          - toolset: clang
+            compiler: clang++-12
+            cxxstd: "03,11,14,17,2a"
+            os: ubuntu-20.04
+            install: clang-12
           - toolset: clang
             cxxstd: "03,11,14,17,2a"
             os: macos-10.15

CMakeLists.txt

@@ -0,0 +1,25 @@
+# Generated by `boostdep --cmake describe`
+# Copyright 2020 Peter Dimov
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+cmake_minimum_required(VERSION 3.5...3.16)
+
+project(boost_describe VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)
+
+add_library(boost_describe INTERFACE)
+add_library(Boost::describe ALIAS boost_describe)
+
+target_include_directories(boost_describe INTERFACE include)
+
+target_link_libraries(boost_describe
+  INTERFACE
+    Boost::mp11
+)
+
+if(BUILD_TESTING AND EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/test/CMakeLists.txt")
+
+  add_subdirectory(test)
+
+endif()
+

README.md

@@ -2,8 +2,8 @@
 
 A C++14 reflection library. Provides macros for describing enumerators and
 struct/class members, and primitives for querying this information. See
-[the documentation](https://pdimov.github.io/describe) for more information
-and usage examples.
+[the documentation](https://www.boost.org/doc/libs/develop/libs/describe/)
+for more information and usage examples.
 
 ## Supported Compilers
 
@@ -16,4 +16,5 @@ Tested on [Travis](https://travis-ci.org/github/pdimov/describe/) and
 
 ## License
 
-Distributed under the [Boost Software License, Version 1.0](http://boost.org/LICENSE_1_0.txt).
+Distributed under the
+[Boost Software License, Version 1.0](http://boost.org/LICENSE_1_0.txt).

doc/.gitignore

@@ -1 +1,2 @@
 /pdf/
+/html/

doc/describe.adoc

@@ -16,6 +16,7 @@ Peter Dimov
 :leveloffset: +1
 
 include::describe/overview.adoc[]
+include::describe/changes.adoc[]
 include::describe/enums.adoc[]
 include::describe/classes.adoc[]
 include::describe/examples.adoc[]

doc/describe/changes.adoc

@@ -0,0 +1,13 @@
+////
+Copyright 2021 Peter Dimov
+Distributed under the Boost Software License, Version 1.0.
+https://www.boost.org/LICENSE_1_0.txt
+////
+
+[#changes]
+# Revision History
+:idprefix:
+
+## Changes in Boost 1.78.0
+
+* Added `has_describe_enumerators`, `has_describe_bases`, `has_describe_members`.

doc/describe/classes.adoc

@@ -1,5 +1,5 @@
 ////
-Copyright 2020 Peter Dimov
+Copyright 2020, 2021 Peter Dimov
 Distributed under the Boost Software License, Version 1.0.
 https://www.boost.org/LICENSE_1_0.txt
 ////
@@ -70,6 +70,8 @@ private:
 
 It takes three member lists, for the public, protected, and private members.
 
+## Retrieving Class Properties
+
 Once a type `T` is annotated, its properties can be retrieved via
 `describe_bases<T, M>` and `describe_members<T, M>` (`M` is a bitmask of
 modifiers such as `mod_public | mod_static | mod_function`).
@@ -84,7 +86,7 @@ excludes them. The other two modifiers work similarly.
 
 `describe_members` takes a bitwise-or combination of the following possible
 modifiers: `mod_public`, `mod_protected`, `mod_private`, `mod_static`,
-`mod_function`, `mod_inherited`, `mod_hidden`.
+`mod_function`, `mod_any_member`, `mod_inherited`, `mod_hidden`.
 
 The access modifiers work the same as with `describe_bases`.
 
@@ -97,6 +99,9 @@ the nonstatic members are returned.
 When `mod_function` is present, the member functions are returned, otherwise
 the data members are returned.
 
+When `mod_any_member` is present, `mod_static` and `mod_function` are ignored
+and all members are returned regardless of kind.
+
 When `mod_inherited` is present, members of base classes are also returned.
 
 When `mod_hidden` is present, hidden inherited members are included. A member

doc/describe/enums.adoc

@@ -47,6 +47,28 @@ For defining `enum class E2` instead, use `BOOST_DEFINE_ENUM_CLASS`. To add
 an underlying type, i.e. `enum E3: int` or `enum class E4: unsigned char`,
 use `BOOST_DEFINE_FIXED_ENUM` and `BOOST_DEFINE_FIXED_ENUM_CLASS`, respectively.
 
+If your enumeration type is nested inside a class or a `struct`, use the
+`BOOST_DESCRIBE_NESTED_ENUM` macro next to the `enum`, as follows:
+
+```
+class X
+{
+private:
+
+    enum class E
+    {
+        v1,
+        v2
+    };
+
+    BOOST_DESCRIBE_NESTED_ENUM(E, v1, v2)
+
+public:
+
+    // ...
+};
+```
+
 Once an enumeration type `E` is annotated, one can use `describe_enumerators<E>`
 to obtain a _descriptor list_. (`describe_enumerators` is defined in the
 `boost::describe` namespace, in `<boost/describe/enumerators.hpp>`.)

doc/describe/examples.adoc

@@ -86,12 +86,43 @@ change its state and hence cannot violate its invariant.)
 include::../../example/print_function.cpp[lines=5..-1]
 ----
 
+[#example_hash_value]
+## Implementing hash_value
+
+This example defines a universal `hash_value` overload that
+computes the hash value of an annotated struct or class. It
+does so by iterating over the described bases and members and
+calling `boost::hash_combine` on each.
+
+The overload is defined in namespace `app` in order to apply
+to all annotated classes also defined in `app`.
+
+[source]
+----
+include::../../example/hash_value.cpp[lines=5..-1]
+----
+
+[#example_equality]
+## Implementing operator==
+
+This example defines a universal `operator==` overload that
+iterates over the described bases and members and compares
+them for equality using `==`.
+
+The overload is defined in namespace `app` in order to apply
+to all annotated classes also defined in `app`.
+
+[source]
+----
+include::../../example/equality.cpp[lines=5..-1]
+----
+
 [#example_to_json]
 ## Automatic Conversion to JSON
 
 This example defines a universal `tag_invoke` overload that
 automatically converts an annotated struct to a
-http://master.json.cpp.al[Boost.JSON] value by iterating
+http://boost.org/libs/json[Boost.JSON] value by iterating
 over the described public members and adding them to the return
 `boost::json::object`.
 
@@ -136,7 +167,7 @@ include::../../example/serialization.cpp[lines=5..-1]
 
 This example defines a generic `call` function that can be used to
 invoke a member function by name, with the arguments passed in a
-http://master.json.cpp.al[Boost.JSON] array. The result is returned
+http://boost.org/libs/json[Boost.JSON] array. The result is returned
 in a `boost::json::value`.
 
 [source]
@@ -144,3 +175,14 @@ in a `boost::json::value`.
 include::../../example/json_rpc.cpp[lines=5..-1]
 ----
 
+[#example_console]
+## Interactive Variable Console
+
+This example implements an interactive console that allows printing
+and modifying variables. It uses http://boost.org/libs/json[Boost.JSON]
+for converting the variables to and from a string form.
+
+[source]
+----
+include::../../example/console.cpp[lines=9..-1]
+----

doc/describe/reference.adoc

@@ -1,5 +1,5 @@
 ////
-Copyright 2020 Peter Dimov
+Copyright 2020, 2021 Peter Dimov
 Distributed under the Boost Software License, Version 1.0.
 https://www.boost.org/LICENSE_1_0.txt
 ////
@@ -12,7 +12,8 @@ https://www.boost.org/LICENSE_1_0.txt
 
 ```
 #define BOOST_DESCRIBE_ENUM(E, ...) /*...*/
-#define BOOST_DESCRIBE_ENUM_CLASS(E, ...) /*...*/
+
+#define BOOST_DESCRIBE_NESTED_ENUM(E, ...) /*...*/
 
 #define BOOST_DEFINE_ENUM(E, ...) \
     enum E { __VA_ARGS__ }; BOOST_DESCRIBE_ENUM(E, __VA_ARGS__)
@@ -48,6 +49,13 @@ struct Di
 ```
 where `vi` is the corresponding identifier passed to the macro.
 
+### BOOST_DESCRIBE_NESTED_ENUM
+
+`BOOST_DESCRIBE_NESTED_ENUM(E, v1, v2, ..., vN)` is similar to
+`BOOST_DESCRIBE_ENUM` and is used to annotate enumeration types nested inside
+class (or `struct`) types. It should be placed in the class type where the
+`enum` is defined.
+
 ### BOOST_DEFINE_ENUM
 
 `BOOST_DEFINE_ENUM(E, v1, v2, ..., vN)` is a convenience macro expanding to
@@ -88,6 +96,8 @@ namespace describe {
 
 template<class E> using describe_enumerators = /*...*/;
 
+template<class E> using has_describe_enumerators = /*...*/;
+
 } }
 ```
 
@@ -108,6 +118,14 @@ struct Di
 ```
 where `vi` is the i-th enumerator.
 
+If `E` is not a described enumeration type, `describe_enumerators<E>` causes
+a substitution failure.
+
+### has_describe_enumerators<E>
+
+`has_describe_enumerators<E>::value` is `true` when `E` is a described
+enumeration type, `false` otherwise.
+
 ## <boost/describe/class.hpp>
 
 ```
@@ -190,8 +208,9 @@ enum modifiers
     mod_virtual = 8,
     mod_static = 16,
     mod_function = 32,
-    mod_inherited = 64,
-    mod_hidden = 128,
+    mod_any_member = 64,
+    mod_inherited = 128,
+    mod_hidden = 256,
 };
 
 constexpr modifiers mod_any_access = static_cast<modifiers>( mod_public | mod_protected | mod_private );
@@ -211,6 +230,7 @@ following flags:
 * `mod_virtual` - returned when a base class is a virtual base
 * `mod_static` - returns static members (when not given, returns nonstatic members)
 * `mod_function` - returns member functions (when not given, returns data members)
+* `mod_any_member` - overrides `mod_static` and `mod_function` and returns all members regardless of kind
 * `mod_inherited` - includes members of base classes
 * `mod_hidden` - includes hidden inherited members
 
@@ -222,6 +242,8 @@ namespace describe {
 
 template<class T, unsigned M> using describe_bases = /*...*/;
 
+template<class T> using has_describe_bases = /*...*/;
+
 } }
 ```
 
@@ -247,6 +269,18 @@ where `type` is the type of the base class, and `modifiers` are a bitwise-or
 combination of `mod_public`, `mod_protected`, `mod_private`, and `mod_virtual`
 that reflects the properties of the base class.
 
+If `T` is not a described class type, `describe_bases<T, M>` causes a
+substitution failure.
+
+### has_describe_bases<T>
+
+`has_describe_bases<T>::value` is `true` when `T` is a described class type,
+`false` otherwise.
+
+Since the library does not provide a way to describe bases and members separately,
+`has_describe_bases` and `has_describe_members` are, in practice, synonyms. They
+are provided separately for consistency.
+
 ## <boost/describe/members.hpp>
 
 ```
@@ -255,14 +289,16 @@ namespace describe {
 
 template<class T, unsigned M> using describe_members = /*...*/;
 
+template<class T> using has_describe_members = /*...*/;
+
 } }
 ```
 
 ### describe_members<T, M>
 
 `M` must be a bitwise-or combination of `mod_public`, `mod_protected`,
-`mod_private`, `mod_static`, `mod_function`, `mod_inherited`, and
-`mod_hidden`, and acts as a filter.
+`mod_private`, `mod_static`, `mod_function`, `mod_any_member`,
+`mod_inherited`, and `mod_hidden`, and acts as a filter.
 
 `describe_members<T, M>` returns `L<D1, D2, ..., Dn>`, where `L` is a class
 template of the form
@@ -284,6 +320,18 @@ member, and `modifiers` are a bitwise-or combination of `mod_public`,
 `mod_protected`, `mod_private`, `mod_static`, `mod_function`, `mod_inherited`,
 and `mod_hidden` that reflects the properties of the member.
 
+If `T` is not a described class type, `describe_members<T, M>` causes a
+substitution failure.
+
+### has_describe_members<T>
+
+`has_describe_members<T>::value` is `true` when `T` is a described class type,
+`false` otherwise.
+
+Since the library does not provide a way to describe bases and members separately,
+`has_describe_bases` and `has_describe_members` are, in practice, synonyms. They
+are provided separately for consistency.
+
 ## <boost/describe.hpp>
 
 This convenience header includes all the headers previously

example/console.cpp

@@ -0,0 +1,129 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#if defined(_MSC_VER)
+# pragma warning(disable: 4702) // unreachable code
+#endif
+
+#include <boost/describe.hpp>
+#include <boost/mp11.hpp>
+#include <boost/json.hpp>
+#include <boost/utility/string_view.hpp>
+#include <string>
+#include <stdexcept>
+#include <vector>
+#include <map>
+#include <iostream>
+
+// get variable
+
+template<class Scope> boost::json::value get( Scope& scope, boost::string_view name )
+{
+    using Md = boost::describe::describe_members<Scope, boost::describe::mod_public>;
+
+    bool found = false;
+    boost::json::value result;
+
+    boost::mp11::mp_for_each<Md>([&](auto D) {
+
+        if( !found && name == D.name )
+        {
+            result = boost::json::value_from( scope.*D.pointer );
+            found = true;
+        }
+
+    });
+
+    if( !found )
+    {
+        throw std::invalid_argument(
+            std::string( "'" ) + std::string( name ) + "': no such variable" );
+    }
+
+    return result;
+}
+
+// set variable
+
+template<class T> void set_impl( T & t, boost::string_view /*name*/, boost::json::value const& value )
+{
+    t = boost::json::value_to<T>( value );
+}
+
+template<class T> void set_impl( T const & /*t*/, boost::string_view name, boost::json::value const& /*value*/ )
+{
+    throw std::invalid_argument(
+        std::string( "'" ) + std::string( name ) + "': variable cannot be modified" );
+}
+
+template<class Scope> void set( Scope& scope, boost::string_view name, boost::json::value const& value )
+{
+    using Md = boost::describe::describe_members<Scope, boost::describe::mod_public>;
+
+    bool found = false;
+
+    boost::mp11::mp_for_each<Md>([&](auto D) {
+
+        if( !found && name == D.name )
+        {
+            set_impl( scope.*D.pointer, name, value );
+            found = true;
+        }
+
+    });
+
+    if( !found )
+    {
+        throw std::invalid_argument(
+            std::string( "'" ) + std::string( name ) + "': no such variable" );
+    }
+}
+
+//
+
+struct globals
+{
+    std::string const help = "Enter a variable name ('x', 'y', 'v', or 'm') to print its value; enter variable=value to assign a new value to a variable. Values are in JSON format.";
+
+    int x = 1;
+
+    double y = 3.14;
+
+    std::vector<int> v{ 1, 2, 3 };
+
+    std::map<std::string, double> m{ { "BTC", 44898.68 }, { "ETH", 1386.57 } };
+};
+
+BOOST_DESCRIBE_STRUCT( globals, (), (help, x, y, v, m) )
+
+int main()
+{
+    globals g_;
+
+    for( ;; )
+    {
+        std::cout << "\n> ";
+
+        std::string line;
+        std::getline( std::cin, line );
+
+        try
+        {
+            std::size_t i = line.find( '=' );
+
+            if( i != std::string::npos )
+            {
+                set( g_, line.substr( 0, i ), boost::json::parse( line.substr( i + 1 ) ) );
+            }
+            else
+            {
+                std::cout << get( g_, line ) << std::endl;
+            }
+        }
+        catch( std::exception const& x )
+        {
+            std::cout << "Error: " << x.what() << std::endl;
+        }
+    }
+}

example/equality.cpp

@@ -0,0 +1,73 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/describe.hpp>
+#include <boost/mp11.hpp>
+#include <boost/variant2/variant.hpp>
+#include <vector>
+
+using namespace boost::describe;
+
+namespace app
+{
+template<class T,
+    class Bd = describe_bases<T, mod_any_access>,
+    class Md = describe_members<T, mod_any_access>>
+    bool operator==( T const& t1, T const& t2 )
+{
+    bool r = true;
+
+    boost::mp11::mp_for_each<Bd>([&](auto D){
+
+        using B = typename decltype(D)::type;
+        r = r && (B const&)t1 == (B const&)t2;
+
+    });
+
+    boost::mp11::mp_for_each<Md>([&](auto D){
+
+        r = r && t1.*D.pointer == t2.*D.pointer;
+
+    });
+
+    return r;
+}
+
+struct A
+{
+    int x = 1;
+};
+
+BOOST_DESCRIBE_STRUCT(A, (), (x))
+
+struct B
+{
+    int y = 2;
+};
+
+BOOST_DESCRIBE_STRUCT(B, (), (y))
+
+struct C
+{
+    std::vector<boost::variant2::variant<A, B>> v;
+};
+
+BOOST_DESCRIBE_STRUCT(C, (), (v))
+
+} // namespace app
+
+#include <iostream>
+
+int main()
+{
+    app::C c1, c2, c3;
+
+    c1.v.push_back( app::A{} );
+    c2.v.push_back( app::A{} );
+    c3.v.push_back( app::B{} );
+
+    std::cout << std::boolalpha
+        << ( c1 == c2 ) << ' '
+        << ( c1 == c3 ) << std::endl;
+}

example/hash_value.cpp

@@ -0,0 +1,72 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/describe.hpp>
+#include <boost/mp11.hpp>
+#include <boost/container_hash/hash.hpp>
+#include <boost/variant2/variant.hpp>
+#include <vector>
+
+using namespace boost::describe;
+
+namespace app
+{
+
+template<class T,
+    class Bd = describe_bases<T, mod_any_access>,
+    class Md = describe_members<T, mod_any_access>>
+    std::size_t hash_value( T const & t )
+{
+    std::size_t r = 0;
+
+    boost::mp11::mp_for_each<Bd>([&](auto D){
+
+        using B = typename decltype(D)::type;
+        boost::hash_combine( r, (B const&)t );
+
+    });
+
+    boost::mp11::mp_for_each<Md>([&](auto D){
+
+        boost::hash_combine( r, t.*D.pointer );
+
+    });
+
+    return r;
+}
+
+struct A
+{
+    int x = 1;
+};
+
+BOOST_DESCRIBE_STRUCT(A, (), (x))
+
+struct B
+{
+    int y = 2;
+};
+
+BOOST_DESCRIBE_STRUCT(B, (), (y))
+
+struct C
+{
+    std::vector<boost::variant2::variant<A, B>> v;
+};
+
+BOOST_DESCRIBE_STRUCT(C, (), (v))
+
+} // namespace app
+
+#include <iostream>
+
+int main()
+{
+    app::C c;
+
+    c.v.push_back( app::A{} );
+    c.v.push_back( app::B{} );
+
+    std::cout << boost::hash<app::C>()( c ) << std::endl;
+}

example/string_to_enum.cpp

@@ -12,7 +12,8 @@
 [[noreturn]] void throw_invalid_name( char const * name, char const * type )
 {
     throw std::runtime_error(
-        std::string( "Invalid enumerator name '" ) + name + "' for enum type '" + type + "'" );
+        std::string( "Invalid enumerator name '" ) + name
+        + "' for enum type '" + type + "'" );
 }
 
 template<class E> E string_to_enum( char const * name )

include/boost/describe/bases.hpp

@@ -1,16 +1,18 @@
 #ifndef BOOST_DESCRIBE_BASES_HPP_INCLUDED
 #define BOOST_DESCRIBE_BASES_HPP_INCLUDED
 
-// Copyright 2020 Peter Dimov
+// 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/modifiers.hpp>
+#include <boost/describe/detail/void_t.hpp>
 #include <boost/describe/detail/config.hpp>
 
 #if defined(BOOST_DESCRIBE_CXX11)
 
 #include <boost/mp11/algorithm.hpp>
+#include <type_traits>
 
 namespace boost
 {
@@ -26,10 +28,20 @@ template<unsigned M> struct base_filter
     template<class T> using fn = mp11::mp_bool< ( M & mod_any_access & T::modifiers ) != 0 >;
 };
 
+template<class T, class En = void> struct has_describe_bases: std::false_type
+{
+};
+
+template<class T> struct has_describe_bases<T, void_t<_describe_bases<T>>>: std::true_type
+{
+};
+
 } // namespace detail
 
 template<class T, unsigned M> using describe_bases = mp11::mp_copy_if_q<detail::_describe_bases<T>, detail::base_filter<M>>;
 
+template<class T> using has_describe_bases = detail::has_describe_bases<T>;
+
 } // namespace describe
 } // namespace boost
 

include/boost/describe/detail/void_t.hpp

@@ -0,0 +1,32 @@
+#ifndef BOOST_DESCRIBE_DETAIL_VOID_T_HPP_INCLUDED
+#define BOOST_DESCRIBE_DETAIL_VOID_T_HPP_INCLUDED
+
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/describe/detail/config.hpp>
+
+#if defined(BOOST_DESCRIBE_CXX11)
+
+namespace boost
+{
+namespace describe
+{
+namespace detail
+{
+
+template<class...> struct make_void
+{
+    using type = void;
+};
+
+template<class... T> using void_t = typename make_void<T...>::type;
+
+} // namespace detail
+} // namespace describe
+} // namespace boost
+
+#endif // defined(BOOST_DESCRIBE_CXX11)
+
+#endif // #ifndef BOOST_DESCRIBE_DETAIL_VOID_T_HPP_INCLUDED

include/boost/describe/enumerators.hpp

@@ -1,21 +1,43 @@
 #ifndef BOOST_DESCRIBE_ENUMERATORS_HPP_INCLUDED
 #define BOOST_DESCRIBE_ENUMERATORS_HPP_INCLUDED
 
-// Copyright 2020 Peter Dimov
+// 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/detail/void_t.hpp>
 #include <boost/describe/detail/config.hpp>
 
 #if defined(BOOST_DESCRIBE_CXX11)
 
+#include <type_traits>
+
 namespace boost
 {
 namespace describe
 {
 
+// describe_enumerators<E>
+
 template<class E> using describe_enumerators = decltype( boost_enum_descriptor_fn( static_cast<E*>(0) ) );
 
+// has_describe_enumerators<E>
+
+namespace detail
+{
+
+template<class E, class En = void> struct has_describe_enumerators: std::false_type
+{
+};
+
+template<class E> struct has_describe_enumerators<E, void_t<describe_enumerators<E>>>: std::true_type
+{
+};
+
+} // namespace detail
+
+template<class E> using has_describe_enumerators = detail::has_describe_enumerators<E>;
+
 } // namespace describe
 } // namespace boost
 

include/boost/describe/members.hpp

@@ -7,6 +7,8 @@
 
 #include <boost/describe/modifiers.hpp>
 #include <boost/describe/bases.hpp>
+#include <boost/describe/detail/void_t.hpp>
+#include <boost/describe/detail/config.hpp>
 
 #if defined(BOOST_DESCRIBE_CXX11)
 
@@ -15,6 +17,7 @@
 #include <boost/mp11/integral.hpp>
 #include <boost/mp11/list.hpp>
 #include <boost/mp11/bind.hpp>
+#include <type_traits>
 
 namespace boost
 {
@@ -129,17 +132,29 @@ template<class T, unsigned M> using describe_members = mp11::mp_eval_if_c<(M & m
 template<unsigned M> struct member_filter
 {
     template<class T> using fn = mp11::mp_bool<
-        ( M & mod_any_access & T::modifiers ) != 0 &&
-        ( M & mod_static ) == ( T::modifiers & mod_static ) &&
-        ( M & mod_function ) == ( T::modifiers & mod_function ) &&
-        ( M & mod_hidden ) >= ( T::modifiers & mod_hidden )
+        (M & mod_any_access & T::modifiers) != 0 &&
+        ( (M & mod_any_member) != 0 || (M & mod_static) == (T::modifiers & mod_static) ) &&
+        ( (M & mod_any_member) != 0 || (M & mod_function) == (T::modifiers & mod_function) ) &&
+        (M & mod_hidden) >= (T::modifiers & mod_hidden)
     >;
 };
 
+// has_describe_members
+
+template<class T, class En = void> struct has_describe_members: std::false_type
+{
+};
+
+template<class T> struct has_describe_members<T, void_t<_describe_members<T>>>: std::true_type
+{
+};
+
 } // namespace detail
 
 template<class T, unsigned M> using describe_members = mp11::mp_copy_if_q<detail::describe_members<T, M>, detail::member_filter<M>>;
 
+template<class T> using has_describe_members = detail::has_describe_members<T>;
+
 } // namespace describe
 } // namespace boost
 

include/boost/describe/modifiers.hpp

@@ -20,8 +20,9 @@ enum modifiers
     mod_virtual = 8,
     mod_static = 16,
     mod_function = 32,
-    mod_inherited = 64,
-    mod_hidden = 128,
+    mod_any_member = 64,
+    mod_inherited = 128,
+    mod_hidden = 256,
 };
 
 BOOST_DESCRIBE_ENUM(modifiers,
@@ -31,6 +32,7 @@ BOOST_DESCRIBE_ENUM(modifiers,
     mod_virtual,
     mod_static,
     mod_function,
+    mod_any_member,
     mod_inherited,
     mod_hidden);
 

test/CMakeLists.txt

@@ -0,0 +1,11 @@
+# Copyright 2018, 2021 Peter Dimov
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+include(BoostTestJamfile OPTIONAL RESULT_VARIABLE HAVE_BOOST_TEST)
+
+if(HAVE_BOOST_TEST)
+
+boost_test_jamfile(FILE Jamfile LINK_LIBRARIES Boost::describe Boost::core)
+
+endif()

test/Jamfile

@@ -36,7 +36,10 @@ run members_test3.cpp ;
 run members_test4.cpp ;
 run members_test5.cpp ;
 run members_test6.cpp ;
-run members_test7.cpp : : : <toolset>msvc-14.0:<build>no ;
+run members_test7.cpp
+  : : : <toolset>msvc-14.0:<build>no ;
+run members_test8.cpp ;
+
 run overloaded_test.cpp ;
 run overloaded_test2.cpp ;
 
@@ -45,6 +48,14 @@ compile test_d_type.cpp ;
 compile-fail enum_struct_fail.cpp ;
 compile-fail struct_enum_fail.cpp ;
 
+run class_template_test.cpp ;
+
+run has_enumerators_test.cpp ;
+run has_bases_test.cpp ;
+run has_members_test.cpp ;
+
+# examples
+
 obj describe_cxx14 : describe_cxx14.cpp ;
 explicit describe_cxx14 ;
 
@@ -62,3 +73,6 @@ run ../example/to_json.cpp : : : $(CXX14) $(JSON) ;
 run ../example/from_json.cpp : : : $(CXX14) $(JSON) ;
 run ../example/serialization.cpp : : : $(CXX14) $(SERIALIZATION) ;
 run ../example/json_rpc.cpp : : : $(CXX14) $(JSON) ;
+run ../example/hash_value.cpp : : : $(CXX14) ;
+run ../example/equality.cpp : : : $(CXX14) ;
+link ../example/console.cpp : $(CXX14) $(JSON) ;

test/class_template_test.cpp

@@ -0,0 +1,143 @@
+// 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/bases.hpp>
+#include <boost/describe/members.hpp>
+#include <boost/describe/class.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/config.hpp>
+
+template<class A1, class A2> struct X
+{
+    A1 a1;
+    A2 a2;
+
+    BOOST_DESCRIBE_CLASS(X, (), (a1, a2), (), ())
+};
+
+template<class B1, class B2> class Y
+{
+private:
+
+    B1 b1;
+    B2 b2;
+
+    BOOST_DESCRIBE_CLASS(Y, (), (), (), (b1, b2))
+};
+
+template<class T1, class T2> class Z: public X<T1, T2>
+{
+private:
+
+    // error: declaration of 'typedef struct X<T1, T2> Z<T1, T2>::X' changes meaning of 'X' (g++)
+    // typedef X<T1, T2> X;
+
+    typedef X<T1, T2> XB;
+
+protected:
+
+    Y<T1, T2> y;
+
+    BOOST_DESCRIBE_CLASS(Z, (XB), (), (y), ())
+};
+
+#if !defined(BOOST_DESCRIBE_CXX14)
+
+#include <boost/config/pragma_message.hpp>
+
+BOOST_PRAGMA_MESSAGE("Skipping test because C++14 is not available")
+int main() {}
+
+#elif defined(BOOST_MSVC) && BOOST_MSVC < 1920
+
+BOOST_PRAGMA_MESSAGE("Skipping test because BOOST_MSVC is below 1920")
+int main() {}
+
+#elif defined(BOOST_MSVC) && BOOST_MSVC >= 1920 && BOOST_MSVC < 1930 && _MSVC_LANG <= 201703L
+
+BOOST_PRAGMA_MESSAGE("Skipping test because BOOST_MSVC is 192x and _MSVC_LANG is 201703L or below")
+int main() {}
+
+#else
+
+#include <boost/mp11.hpp>
+using namespace boost::mp11;
+
+int main()
+{
+    using namespace boost::describe;
+    using namespace boost::mp11;
+
+    {
+        using L = describe_members<X<int, float>, mod_any_access>;
+
+        BOOST_TEST_EQ( mp_size<L>::value, 2 );
+
+        using D1 = mp_at_c<L, 0>;
+        using D2 = mp_at_c<L, 1>;
+
+        BOOST_TEST( D1::pointer == (&X<int, float>::a1) );
+        BOOST_TEST_CSTR_EQ( D1::name, "a1" );
+        BOOST_TEST_EQ( D1::modifiers, mod_public );
+
+        BOOST_TEST( D2::pointer == (&X<int, float>::a2) );
+        BOOST_TEST_CSTR_EQ( D2::name, "a2" );
+        BOOST_TEST_EQ( D2::modifiers, mod_public );
+    }
+
+    {
+        using L = describe_members<Y<int, float>, mod_any_access>;
+
+        BOOST_TEST_EQ( mp_size<L>::value, 2 );
+
+        using D1 = mp_at_c<L, 0>;
+        using D2 = mp_at_c<L, 1>;
+
+        // BOOST_TEST( D1::pointer == (&Y<int, float>::b1) );
+        BOOST_TEST_CSTR_EQ( D1::name, "b1" );
+        BOOST_TEST_EQ( D1::modifiers, mod_private );
+
+        // BOOST_TEST( D2::pointer == (&Y<int, float>::b2) );
+        BOOST_TEST_CSTR_EQ( D2::name, "b2" );
+        BOOST_TEST_EQ( D2::modifiers, mod_private );
+    }
+
+    {
+        using L = describe_members<Z<int, float>, mod_any_access>;
+
+        BOOST_TEST_EQ( mp_size<L>::value, 1 );
+
+        using D1 = mp_at_c<L, 0>;
+
+        // BOOST_TEST( D1::pointer == (&Z<int, float>::y) );
+        BOOST_TEST_CSTR_EQ( D1::name, "y" );
+        BOOST_TEST_EQ( D1::modifiers, mod_protected );
+    }
+
+    {
+        using L = describe_members<Z<int, float>, mod_any_access | mod_inherited>;
+
+        BOOST_TEST_EQ( mp_size<L>::value, 3 );
+
+        using D1 = mp_at_c<L, 0>;
+        using D2 = mp_at_c<L, 1>;
+        using D3 = mp_at_c<L, 2>;
+
+        BOOST_TEST( D1::pointer == (&X<int, float>::a1) );
+        BOOST_TEST_CSTR_EQ( D1::name, "a1" );
+        BOOST_TEST_EQ( D1::modifiers, mod_public | mod_inherited );
+
+        BOOST_TEST( D2::pointer == (&X<int, float>::a2) );
+        BOOST_TEST_CSTR_EQ( D2::name, "a2" );
+        BOOST_TEST_EQ( D2::modifiers, mod_public | mod_inherited );
+
+        // BOOST_TEST( D3::pointer == (&Z<int, float>::y) );
+        BOOST_TEST_CSTR_EQ( D3::name, "y" );
+        BOOST_TEST_EQ( D3::modifiers, mod_protected );
+    }
+
+    return boost::report_errors();
+}
+
+#endif // !defined(BOOST_DESCRIBE_CXX14)

test/has_bases_test.cpp

@@ -0,0 +1,55 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/describe/bases.hpp>
+#include <boost/describe/class.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+
+#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 X1 {};
+BOOST_DESCRIBE_STRUCT(X1, (), ())
+
+class X2
+{
+    BOOST_DESCRIBE_CLASS(X2, (), (), (), ())
+};
+
+struct X3 {};
+class X4 {};
+union X5 {};
+
+int main()
+{
+    using boost::describe::has_describe_bases;
+
+#if defined(BOOST_DESCRIBE_CXX14)
+
+    BOOST_TEST_TRAIT_TRUE((has_describe_bases<X1>));
+    BOOST_TEST_TRAIT_TRUE((has_describe_bases<X2>));
+
+#else
+
+    BOOST_TEST_TRAIT_FALSE((has_describe_bases<X1>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_bases<X2>));
+
+#endif
+
+    BOOST_TEST_TRAIT_FALSE((has_describe_bases<X3>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_bases<X4>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_bases<X5>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_bases<int>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_bases<void>));
+
+    return boost::report_errors();
+}
+
+#endif // !defined(BOOST_DESCRIBE_CXX11)

test/has_enumerators_test.cpp

@@ -0,0 +1,58 @@
+// Copyright 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_trait.hpp>
+
+#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
+
+enum E1 { v1 };
+BOOST_DESCRIBE_ENUM(E1, v1)
+
+enum class E2 { v2 };
+BOOST_DESCRIBE_ENUM(E2, v2)
+
+BOOST_DEFINE_ENUM(E3, v3);
+BOOST_DEFINE_ENUM_CLASS(E4, v4)
+
+enum E5 { v5 };
+enum class E6 { v6 };
+
+int main()
+{
+    using boost::describe::has_describe_enumerators;
+
+#if defined(BOOST_DESCRIBE_CXX14)
+
+    BOOST_TEST_TRAIT_TRUE((has_describe_enumerators<E1>));
+    BOOST_TEST_TRAIT_TRUE((has_describe_enumerators<E2>));
+    BOOST_TEST_TRAIT_TRUE((has_describe_enumerators<E3>));
+    BOOST_TEST_TRAIT_TRUE((has_describe_enumerators<E4>));
+
+#else
+
+    BOOST_TEST_TRAIT_FALSE((has_describe_enumerators<E1>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_enumerators<E2>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_enumerators<E3>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_enumerators<E4>));
+
+#endif
+
+    BOOST_TEST_TRAIT_FALSE((has_describe_enumerators<E5>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_enumerators<E6>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_enumerators<int>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_enumerators<void>));
+
+    return boost::report_errors();
+}
+
+#endif // !defined(BOOST_DESCRIBE_CXX11)

test/has_members_test.cpp

@@ -0,0 +1,55 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/describe/members.hpp>
+#include <boost/describe/class.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+
+#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 X1 {};
+BOOST_DESCRIBE_STRUCT(X1, (), ())
+
+class X2
+{
+    BOOST_DESCRIBE_CLASS(X2, (), (), (), ())
+};
+
+struct X3 {};
+class X4 {};
+union X5 {};
+
+int main()
+{
+    using boost::describe::has_describe_members;
+
+#if defined(BOOST_DESCRIBE_CXX14)
+
+    BOOST_TEST_TRAIT_TRUE((has_describe_members<X1>));
+    BOOST_TEST_TRAIT_TRUE((has_describe_members<X2>));
+
+#else
+
+    BOOST_TEST_TRAIT_FALSE((has_describe_members<X1>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_members<X2>));
+
+#endif
+
+    BOOST_TEST_TRAIT_FALSE((has_describe_members<X3>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_members<X4>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_members<X5>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_members<int>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_members<void>));
+
+    return boost::report_errors();
+}
+
+#endif // !defined(BOOST_DESCRIBE_CXX11)

test/members_test8.cpp

@@ -0,0 +1,67 @@
+// 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/members.hpp>
+#include <boost/describe/class.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+struct A
+{
+    int m1;
+    static int m2;
+    int f1() const { return m1; }
+    static int f2() { return m2; }
+};
+
+BOOST_DESCRIBE_STRUCT(A, (), (m1, m2, f1, f2))
+
+int A::m2;
+
+#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>
+
+int main()
+{
+    using namespace boost::describe;
+    using namespace boost::mp11;
+
+    {
+        using L = describe_members<A, mod_any_access | mod_any_member>;
+
+        BOOST_TEST_EQ( mp_size<L>::value, 4 );
+
+        using D1 = mp_at_c<L, 0>;
+        using D2 = mp_at_c<L, 1>;
+        using D3 = mp_at_c<L, 2>;
+        using D4 = mp_at_c<L, 3>;
+
+        BOOST_TEST( D1::pointer == &A::m1 );
+        BOOST_TEST_CSTR_EQ( D1::name, "m1" );
+        BOOST_TEST_EQ( D1::modifiers, mod_public );
+
+        BOOST_TEST( D2::pointer == &A::m2 );
+        BOOST_TEST_CSTR_EQ( D2::name, "m2" );
+        BOOST_TEST_EQ( D2::modifiers, mod_public | mod_static );
+
+        BOOST_TEST( D3::pointer == &A::f1 );
+        BOOST_TEST_CSTR_EQ( D3::name, "f1" );
+        BOOST_TEST_EQ( D3::modifiers, mod_public | mod_function );
+
+        BOOST_TEST( D4::pointer == &A::f2 );
+        BOOST_TEST_CSTR_EQ( D4::name, "f2" );
+        BOOST_TEST_EQ( D4::modifiers, mod_public | mod_static | mod_function );
+    }
+
+    return boost::report_errors();
+}
+
+#endif // !defined(BOOST_DESCRIBE_CXX14)