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Rework CountMembers<T> #17

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Merged
christianparpart merged 1 commit into from
Dec 13, 2024
Merged

Rework CountMembers<T> #17

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50 changes: 15 additions & 35 deletions include/reflection-cpp/reflection.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -101,32 +101,11 @@ inline constexpr auto JoinStringLiterals = detail::join<Strs...>();

namespace detail
{
struct any_t final
// This helper-struct is only used by CountMembers to count the number of members in an aggregate type
struct AnyType final
{
#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Weverything"
template <class T>
requires(!std::same_as<T, const char*> && !std::same_as<T, std::nullptr_t>)
[[maybe_unused]] constexpr operator T() const;
#pragma clang diagnostic pop
#elif defined(_MSC_VER)
template <class T>
requires(!std::same_as<T, const char*> && !std::same_as<T, std::nullptr_t>)
[[maybe_unused]] constexpr operator T() const;
#else
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wmissing-declarations"
template <class T>
requires(!std::same_as<T, const char*> && !std::same_as<T, std::nullptr_t>)
[[maybe_unused]] constexpr operator T() const;
#pragma GCC diagnostic pop
#endif

[[maybe_unused]] constexpr operator std::string_view() const
{
return {};
}
};

template <auto Ptr>
Expand All @@ -142,21 +121,22 @@ namespace detail
// return std::source_location::current().function_name();
return REFLECTION_PRETTY_FUNCTION;
}

template <class AggregateType, class... Args>
requires(std::is_aggregate_v<AggregateType>)
constexpr inline auto CountMembers = []() constexpr {
if constexpr (requires { AggregateType { Args {}..., AnyType {} }; })
return CountMembers<AggregateType, Args..., AnyType>;
else
return sizeof...(Args);
}();

} // namespace detail

template <class T, class... Args>
// Count the number of members in an aggregate type.
template <class T>
requires(std::is_aggregate_v<std::remove_cvref_t<T>>)
inline constexpr auto CountMembers = [] {
using V = std::remove_cvref_t<T>;
if constexpr (requires { V { Args {}..., detail::any_t {} }; })
{
return CountMembers<V, Args..., detail::any_t>;
}
else
{
return sizeof...(Args);
}
}();
constexpr inline auto CountMembers = detail::CountMembers<std::remove_cvref_t<T>>;

constexpr size_t MaxReflectionMemerCount = 50; // should go as high as 256, I guess? for now 30 is enough

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