sol2/include/sol/ebco.hpp

// sol3

// The MIT License (MIT)

// Copyright (c) 2013-2020 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
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// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:

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#ifndef SOL_EBCO_HPP
#define SOL_EBCO_HPP

#include <type_traits>
#include <utility>

namespace sol { namespace detail {

	template <typename T, std::size_t tag = 0, typename = void>
	struct ebco {
		T m_value;

		ebco() = default;
		ebco(const ebco&) = default;
		ebco(ebco&&) = default;
		ebco& operator=(const ebco&) = default;
		ebco& operator=(ebco&&) = default;
		ebco(const T& v) noexcept(std::is_nothrow_copy_constructible_v<T>) : m_value(v) {};
		ebco(T&& v) noexcept(std::is_nothrow_move_constructible_v<T>) : m_value(std::move(v)) {};
		ebco& operator=(const T& v) noexcept(std::is_nothrow_copy_assignable_v<T>) {
			m_value = v;
			return *this;
		}
		ebco& operator=(T&& v) noexcept(std::is_nothrow_move_assignable_v<T>) {
			m_value = std::move(v);
			return *this;
		};
		template <typename Arg, typename... Args,
			typename = std::enable_if_t<!std::is_same_v<std::remove_reference_t<std::remove_cv_t<Arg>>,
			                                 ebco> && !std::is_same_v<std::remove_reference_t<std::remove_cv_t<Arg>>, T> && (sizeof...(Args) > 0 || !std::is_convertible_v<Arg, T>)>>
		ebco(Arg&& arg, Args&&... args) noexcept(std::is_nothrow_constructible_v<T, Arg, Args...>)
		: m_value(std::forward<Arg>(arg), std::forward<Args>(args)...) {
		}

		T& value() & noexcept {
			return m_value;
		}

		T const& value() const& noexcept {
			return m_value;
		}

		T&& value() && noexcept {
			return std::move(m_value);
		}
	};

	template <typename T, std::size_t tag>
	struct ebco<T, tag, std::enable_if_t<!std::is_reference_v<T> && std::is_class_v<T> && !std::is_final_v<T>>> : T {
		ebco() = default;
		ebco(const ebco&) = default;
		ebco(ebco&&) = default;
		ebco(const T& v) noexcept(std::is_nothrow_copy_constructible_v<T>) : T(v) {};
		ebco(T&& v) noexcept(std::is_nothrow_move_constructible_v<T>) : T(std::move(v)) {};
		template <typename Arg, typename... Args,
			typename = std::enable_if_t<!std::is_same_v<std::remove_reference_t<std::remove_cv_t<Arg>>,
			                                 ebco> && !std::is_same_v<std::remove_reference_t<std::remove_cv_t<Arg>>, T> && (sizeof...(Args) > 0 || !std::is_convertible_v<Arg, T>)>>
		ebco(Arg&& arg, Args&&... args) noexcept(std::is_nothrow_constructible_v<T, Arg, Args...>) : T(std::forward<Arg>(arg), std::forward<Args>(args)...) {
		}

		ebco& operator=(const ebco&) = default;
		ebco& operator=(ebco&&) = default;
		ebco& operator=(const T& v) noexcept(std::is_nothrow_copy_assignable_v<T>) {
			static_cast<T&>(*this) = v;
			return *this;
		}
		ebco& operator=(T&& v) noexcept(std::is_nothrow_move_assignable_v<T>) {
			static_cast<T&>(*this) = std::move(v);
			return *this;
		};

		T& value() & noexcept {
			return static_cast<T&>(*this);
		}

		T const& value() const& noexcept {
			return static_cast<T const&>(*this);
		}

		T&& value() && noexcept {
			return std::move(static_cast<T&>(*this));
		}
	};

	template <typename T, std::size_t tag>
	struct ebco<T&, tag> {
	private:
		T* m_ref;

	public:
		ebco() = default;
		ebco(const ebco&) = default;
		ebco(ebco&&) = default;
		ebco(T& v) noexcept : m_ref(std::addressof(v)) {};

		ebco& operator=(const ebco&) = default;
		ebco& operator=(ebco&&) = default;
		ebco& operator=(T& v) noexcept {
			m_ref = std::addressof(v);
			return *this;
		}

		T& value() const noexcept {
			return *(const_cast<ebco<T&, tag>&>(*this).m_ref);
		}
	};

	template <typename T, std::size_t tag>
	struct ebco<T&&, tag> {
		T&& ref;

		ebco() = default;
		ebco(const ebco&) = delete;
		ebco(ebco&&) = default;
		ebco(T&& v) noexcept : ref(v) {};

		ebco& operator=(const ebco&) = delete;
		ebco& operator=(ebco&&) = delete;

		T& value() & noexcept {
			return ref;
		}

		const T& value() const& noexcept {
			return ref;
		}

		T&& value() && noexcept {
			return std::move(ref);
		}
	};

}} // namespace sol::detail

#endif // SOL_EBCO_HPP