Add new interface for attributes

examples/src/attributes.cpp

@@ -4,6 +4,7 @@
 template <typename T>
 struct AttributeData {
   T value;
+  constexpr auto operator==(const AttributeData<T>&) const -> bool = default;
 };
 
 
@@ -19,8 +20,25 @@ ATTRIBUTE_STRUCT(SomeStruct,
   std::string field3;
 );
 
-static_assert(SomeStruct::GetAttribute<0>().value == 2);
-static_assert(SomeStruct::GetAttribute<2>().value == "HEY!");
+static_assert(utempl::GetAttributes<SomeStruct>() 
+  == utempl::Tuple{
+      AttributeData<int>{.value = 2}, 
+      utempl::NoInfo{},
+      AttributeData<std::string>{.value = "HEY!"}});
+
+
+struct SomeOtherStruct {
+  static_assert(utempl::OpenStruct<SomeOtherStruct>());
+  utempl::FieldAttribute<utempl::FieldType<int>, int> field1;
+  utempl::FieldAttribute<utempl::FieldType<int>, void> field2;
+  static_assert(utempl::CloseStruct());
+};
+
+static_assert(utempl::GetAttributes<SomeOtherStruct>() 
+  == utempl::Tuple{
+      utempl::kTypeList<int>,
+      utempl::kTypeList<void>});
+
 
 
 

include/utempl/attributes.hpp

@@ -1,5 +1,6 @@
 #include <utempl/loopholes/counter.hpp>
 #include <utempl/meta_info.hpp>
+#include <utempl/utils.hpp>
 
 
 namespace utempl {
@@ -14,22 +15,70 @@ template <typename T>
 struct AttributesCounterTag {};
 
 
-template <typename Current, auto f = []{}, auto = AddTypeToTag<impl::AttributesTag, Current, decltype(f)>()>
-struct CurrentSetter {};
-
 
 } // namespace impl
 
 
+template <
+  typename T,
+  typename...,
+  auto f = []{},
+  auto = AddTypeToTag<impl::AttributesTag, T, decltype(f)>()
+>
+consteval auto OpenStruct() -> bool {
+  return true;
+};
 
+template <
+  typename...,
+  auto f = []{},
+  auto I = loopholes::CountValue<impl::AttributesTag, decltype(f)>(),
+  auto II = (I > 2) ? I - 2 : I - 1,
+  typename T = decltype(Magic(loopholes::Getter<MetaInfoKey<II, impl::AttributesTag>{}>{}))::Type,
+  auto = AddTypeToTag<impl::AttributesTag, T, decltype(f)>()
+>
+consteval auto CloseStruct() -> bool {
+  return true;
+};
+
+
+
+struct NoInfo {
+  consteval auto operator==(const NoInfo&) const -> bool = default;
+};
+
+
+template <typename T>
+struct FieldType {
+  using Type = T;
+};
+
+
+namespace impl {
+
+template <
+  typename T,
+  typename... Ts,
+  auto f = []{},
+  typename Current = decltype(GetCurrentTagType<impl::AttributesTag, decltype(f)>())::Type,
+  auto = AddTypeToTag<impl::AttributesCounterTag<Current>, TypeList<Ts...>, decltype(f)>()
+>
+consteval auto FieldAttribute() -> T::Type;
+
+} // namespace impl
+
+template <typename... Ts>
+using FieldAttribute = decltype(impl::FieldAttribute<Ts...>());
 
 
 #define ATTRIBUTE_STRUCT(name, ...) struct name { \
-static_assert((::utempl::impl::CurrentSetter<name>(), true)); \
+static_assert(::utempl::OpenStruct<name>()); \
 template <std::size_t N> \
-static consteval auto GetAttribute(); __VA_ARGS__ }
+static consteval auto GetAttribute(); \
+  __VA_ARGS__ \
+  static_assert(::utempl::CloseStruct());\
+}
 
-struct NoInfo {};
 
 #define GENERIC_ATTRIBUTE(value) \
   template <> \
@@ -45,4 +94,35 @@ struct NoInfo {};
 #define SKIP_ATTRIBUTE() GENERIC_ATTRIBUTE(::utempl::NoInfo{})
 
 
+template <
+  typename T,
+  auto f = []{},
+  bool R = (loopholes::CountValue<impl::AttributesCounterTag<T>, decltype(f)>() > 0)
+>
+concept HasAttributes = R;
+
+template <typename T>
+concept HasMacroAttributes = requires {T::template GetAttribute<0>();};
+
+
+
+template <HasAttributes T>
+consteval auto GetAttributes() requires HasMacroAttributes<T> {
+  constexpr auto I = loopholes::CountValue<impl::AttributesCounterTag<T>>();
+  return [](auto... is) {
+    return Tuple{T::template GetAttribute<is>()...};
+  } | kSeq<I>;
+};
+
+template <typename T>
+consteval auto GetAttributes() {
+  constexpr auto I = loopholes::CountValue<impl::AttributesCounterTag<T>>();
+  return [](auto... is) {
+    return utempl::Tuple{typename decltype(Magic(loopholes::Getter<MetaInfoKey<is, impl::AttributesCounterTag<T>>{}>{}))::Type{}...};
+  } | kSeq<I>;
+};
+
+
+
+
 } // namespace utempl