sol2/include/sol/bind_traits.hpp

// sol2

// The MIT License (MIT)

// Copyright (c) 2013-2021 Rapptz, ThePhD and contributors

// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
// IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

#ifndef SOL_BIND_TRAITS_HPP
#define SOL_BIND_TRAITS_HPP

#include <sol/forward.hpp>
#include <sol/base_traits.hpp>
#include <sol/tuple.hpp>

namespace sol { namespace meta {
	namespace meta_detail {
		template <typename F>
		using detect_deducible_signature = decltype(&F::operator(), void());
	} // namespace meta_detail

	template <typename F>
	using call_operator_deducible = typename is_detected<meta_detail::detect_deducible_signature, F>::type;

	template <typename F>
	constexpr inline bool call_operator_deducible_v = call_operator_deducible<F>::value;

	namespace meta_detail {

		template <std::size_t I, typename T>
		struct void_tuple_element : meta::tuple_element<I, T> { };

		template <std::size_t I>
		struct void_tuple_element<I, std::tuple<>> {
			typedef void type;
		};

		template <std::size_t I, typename T>
		using void_tuple_element_t = typename void_tuple_element<I, T>::type;

		template <bool it_is_noexcept, bool has_c_variadic, typename T, typename R, typename... Args>
		struct basic_traits {
		private:
			using first_type = meta::conditional_t<std::is_void<T>::value, int, T>&;

		public:
			inline static constexpr const bool is_noexcept = it_is_noexcept;
			inline static constexpr bool is_member_function = std::is_void<T>::value;
			inline static constexpr bool has_c_var_arg = has_c_variadic;
			inline static constexpr std::size_t arity = sizeof...(Args);
			inline static constexpr std::size_t free_arity = sizeof...(Args) + static_cast<std::size_t>(!std::is_void<T>::value);
			typedef types<Args...> args_list;
			typedef std::tuple<Args...> args_tuple;
			typedef T object_type;
			typedef R return_type;
			typedef tuple_types<R> returns_list;
			typedef R(function_type)(Args...);
			typedef meta::conditional_t<std::is_void<T>::value, args_list, types<first_type, Args...>> free_args_list;
			typedef meta::conditional_t<std::is_void<T>::value, R(Args...), R(first_type, Args...)> free_function_type;
			typedef meta::conditional_t<std::is_void<T>::value, R (*)(Args...), R (*)(first_type, Args...)> free_function_pointer_type;
			typedef std::remove_pointer_t<free_function_pointer_type> signature_type;
			template <std::size_t i>
			using arg_at = void_tuple_element_t<i, args_tuple>;
		};

		template <typename Signature, bool b = call_operator_deducible<Signature>::value>
		struct fx_traits : public basic_traits<false, false, void, void> { };

		// Free Functions
		template <typename R, typename... Args>
		struct fx_traits<R(Args...), false> : public basic_traits<false, false, void, R, Args...> {
			typedef R (*function_pointer_type)(Args...);
		};

		template <typename R, typename... Args>
		struct fx_traits<R (*)(Args...), false> : public basic_traits<false, false, void, R, Args...> {
			typedef R (*function_pointer_type)(Args...);
		};

		template <typename R, typename... Args>
		struct fx_traits<R(Args..., ...), false> : public basic_traits<false, true, void, R, Args...> {
			typedef R (*function_pointer_type)(Args..., ...);
		};

		template <typename R, typename... Args>
		struct fx_traits<R (*)(Args..., ...), false> : public basic_traits<false, true, void, R, Args...> {
			typedef R (*function_pointer_type)(Args..., ...);
		};

		// Member Functions
		/* C-Style Variadics */
		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...), false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...);
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...), false> : public basic_traits<false, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...);
		};

		/* Const Volatile */
		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) const, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) const;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) const, false> : public basic_traits<false, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) const;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) const volatile, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) const volatile;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) const volatile, false> : public basic_traits<false, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) const volatile;
		};

		/* Member Function Qualifiers */
		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...)&, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) &;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...)&, false> : public basic_traits<false, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) &;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) const&, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) const&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) const&, false> : public basic_traits<false, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) const&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) const volatile&, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) const volatile&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) const volatile&, false> : public basic_traits<false, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) const volatile&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...)&&, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) &&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...)&&, false> : public basic_traits<false, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) &&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) const&&, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) const&&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) const&&, false> : public basic_traits<false, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) const&&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) const volatile&&, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) const volatile&&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) const volatile&&, false> : public basic_traits<false, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) const volatile&&;
		};

#if SOL_IS_ON(SOL_USE_NOEXCEPT_FUNCTION_TYPE)

		template <typename R, typename... Args>
		struct fx_traits<R(Args...) noexcept, false> : public basic_traits<true, false, void, R, Args...> {
			typedef R (*function_pointer_type)(Args...) noexcept;
		};

		template <typename R, typename... Args>
		struct fx_traits<R (*)(Args...) noexcept, false> : public basic_traits<true, false, void, R, Args...> {
			typedef R (*function_pointer_type)(Args...) noexcept;
		};

		template <typename R, typename... Args>
		struct fx_traits<R(Args..., ...) noexcept, false> : public basic_traits<true, true, void, R, Args...> {
			typedef R (*function_pointer_type)(Args..., ...) noexcept;
		};

		template <typename R, typename... Args>
		struct fx_traits<R (*)(Args..., ...) noexcept, false> : public basic_traits<true, true, void, R, Args...> {
			typedef R (*function_pointer_type)(Args..., ...) noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) noexcept;
		};

		/* Const Volatile */
		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) const noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) const noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) const noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) const noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) const volatile noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) const volatile noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) const volatile noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) const volatile noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...)& noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) & noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...)& noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) & noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) const& noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) const& noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) const& noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) const& noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) const volatile& noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) const volatile& noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) const volatile& noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) const volatile& noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...)&& noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) && noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...)&& noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) && noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) const&& noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) const&& noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) const&& noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) const&& noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args...) const volatile&& noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args...) const volatile&& noexcept;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (T::*)(Args..., ...) const volatile&& noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (T::*function_pointer_type)(Args..., ...) const volatile&& noexcept;
		};

#endif // noexcept is part of a function's type

#if SOL_IS_ON(SOL_COMPILER_VCXX) && SOL_IS_ON(SOL_PLATFORM_X86)
		template <typename R, typename... Args>
		struct fx_traits<R __stdcall(Args...), false> : public basic_traits<false, false, void, R, Args...> {
			typedef R(__stdcall* function_pointer_type)(Args...);
		};

		template <typename R, typename... Args>
		struct fx_traits<R(__stdcall*)(Args...), false> : public basic_traits<false, false, void, R, Args...> {
			typedef R(__stdcall* function_pointer_type)(Args...);
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...), false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...);
		};

		/* Const Volatile */
		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) const, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) const;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) const volatile, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) const volatile;
		};

		/* Member Function Qualifiers */
		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...)&, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) &;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) const&, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) const&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) const volatile&, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) const volatile&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...)&&, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) &&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) const&&, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) const&&;
		};

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) const volatile&&, false> : public basic_traits<false, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) const volatile&&;
		};

#if SOL_IS_ON(SOL_USE_NOEXCEPT_FUNCTION_TYPE)

		template <typename R, typename... Args>
		struct fx_traits<R __stdcall(Args...) noexcept, false> : public basic_traits<true, false, void, R, Args...> {
			typedef R(__stdcall* function_pointer_type)(Args...) noexcept;
		};

		template <typename R, typename... Args>
		struct fx_traits<R(__stdcall*)(Args...) noexcept, false> : public basic_traits<true, false, void, R, Args...> {
			typedef R(__stdcall* function_pointer_type)(Args...) noexcept;
		};

		/* __stdcall cannot be applied to functions with varargs*/
		/*template <typename R, typename... Args>
		struct fx_traits<__stdcall R(Args..., ...) noexcept, false> : public basic_traits<true, true, void, R, Args...> {
			typedef R(__stdcall* function_pointer_type)(Args..., ...) noexcept;
		};

		template <typename R, typename... Args>
		struct fx_traits<R (__stdcall *)(Args..., ...) noexcept, false> : public basic_traits<true, true, void, R, Args...> {
			typedef R(__stdcall* function_pointer_type)(Args..., ...) noexcept;
		};*/

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) noexcept;
		};

		/* __stdcall does not work with varargs */
		/*template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args..., ...) noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args..., ...) noexcept;
		};*/

		/* Const Volatile */
		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) const noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) const noexcept;
		};

		/* __stdcall does not work with varargs */
		/*template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args..., ...) const noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args..., ...) const noexcept;
		};*/

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) const volatile noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) const volatile noexcept;
		};

		/* __stdcall does not work with varargs */
		/*template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args..., ...) const volatile noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args..., ...) const volatile noexcept;
		};*/

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...)& noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) & noexcept;
		};

		/* __stdcall does not work with varargs */
		/*template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args..., ...) & noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args..., ...) & noexcept;
		};*/

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) const& noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) const& noexcept;
		};

		/* __stdcall does not work with varargs */
		/*template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args..., ...) const& noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args..., ...) const& noexcept;
		};*/

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) const volatile& noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) const volatile& noexcept;
		};

		/* __stdcall does not work with varargs */
		/*template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args..., ...) const volatile& noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args..., ...) const volatile& noexcept;
		};*/

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...)&& noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) && noexcept;
		};

		/* __stdcall does not work with varargs */
		/*template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args..., ...) && noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args..., ...) && noexcept;
		};*/

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) const&& noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) const&& noexcept;
		};

		/* __stdcall does not work with varargs */
		/*template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args..., ...) const&& noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args..., ...) const&& noexcept;
		};*/

		template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args...) const volatile&& noexcept, false> : public basic_traits<true, false, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args...) const volatile&& noexcept;
		};

		/* __stdcall does not work with varargs */
		/*template <typename T, typename R, typename... Args>
		struct fx_traits<R (__stdcall T::*)(Args..., ...) const volatile&& noexcept, false> : public basic_traits<true, true, T, R, Args...> {
			typedef R (__stdcall T::*function_pointer_type)(Args..., ...) const volatile&& noexcept;
		};*/
#endif // noexcept is part of a function's type
#endif // __stdcall x86 VC++ bug

		template <typename Signature>
		struct fx_traits<Signature, true> : public fx_traits<typename fx_traits<decltype(&Signature::operator())>::function_type, false> { };

		template <typename Signature, bool b = std::is_member_object_pointer<Signature>::value>
		struct callable_traits : public fx_traits<std::decay_t<Signature>> { };

		template <typename R, typename T>
		struct callable_traits<R(T::*), true> {
			typedef meta::conditional_t<std::is_array_v<R>, std::add_lvalue_reference_t<R>, R> return_type;
			typedef return_type Arg;
			typedef T object_type;
			using signature_type = R(T::*);
			inline static constexpr bool is_noexcept = false;
			inline static constexpr bool is_member_function = false;
			inline static constexpr std::size_t arity = 1;
			inline static constexpr std::size_t free_arity = 2;
			typedef std::tuple<Arg> args_tuple;
			typedef types<Arg> args_list;
			typedef types<T, Arg> free_args_list;
			typedef meta::tuple_types<return_type> returns_list;
			typedef return_type(function_type)(T&, return_type);
			typedef return_type (*function_pointer_type)(T&, Arg);
			typedef return_type (*free_function_pointer_type)(T&, Arg);
			template <std::size_t i>
			using arg_at = void_tuple_element_t<i, args_tuple>;
		};

	} // namespace meta_detail

	template <typename Signature>
	using bind_traits = meta_detail::callable_traits<Signature>;

	namespace meta_detail {
		template <typename, bool>
		struct is_probably_stateless_lambda : std::false_type { };

		template <typename T>
		struct is_probably_stateless_lambda<T, true> : std::is_convertible<T, typename bind_traits<T>::function_type*>::type { };
	} // namespace meta_detail

	template <typename T>
	using is_probably_stateless_lambda = typename meta_detail::is_probably_stateless_lambda<T, std::is_empty_v<T> && call_operator_deducible_v<T>>::type;

	template <typename T>
	inline constexpr bool is_probably_stateless_lambda_v = is_probably_stateless_lambda<T>::value;

	template <typename Signature>
	using function_args_t = typename bind_traits<Signature>::args_list;

	template <typename Signature>
	using function_signature_t = typename bind_traits<Signature>::signature_type;

	template <typename Signature>
	using function_return_t = typename bind_traits<Signature>::return_type;
}} // namespace sol::meta

#endif // SOL_BIND_TRAITS_HPP