sol2/sol/stack_push.hpp

// The MIT License (MIT) 

// Copyright (c) 2013-2017 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_STACK_PUSH_HPP
#define SOL_STACK_PUSH_HPP

#include "stack_core.hpp"
#include "raii.hpp"
#include "optional.hpp"
#include "usertype_traits.hpp"
#include "filters.hpp"

#include <memory>
#include <type_traits>
#include <cassert>
#include <limits>
#ifdef SOL_CODECVT_SUPPORT
#include <codecvt>
#include <locale>
#endif // codecvt support
#ifdef SOL_CXX17_FEATURES
#include <string_view>
#include <variant>
#endif // C++17

namespace sol {
	namespace stack {
		inline int push_environment_of(lua_State* L, int index = -1) {
#if SOL_LUA_VERSION < 502
			// Use lua_getfenv
			lua_getfenv(L, index);
			return 1;
#else
			// Use upvalues as explained in Lua 5.2 and beyond's manual
			if (lua_getupvalue(L, index, 1) == nullptr) {
				push(L, lua_nil);
				return 1;
			}
#endif
			return 1;
		}

		template <typename T>
		int push_environment_of(const T& target) {
			target.push();
			return push_environment_of(target.lua_state(), -1) + 1;
		}

		template <typename T>
		struct pusher<detail::as_value_tag<T>> {
			template <typename F, typename... Args>
			static int push_fx(lua_State* L, F&& f, Args&&... args) {
				// Basically, we store all user-data like this:
				// If it's a movable/copyable value (no std::ref(x)), then we store the pointer to the new
				// data in the first sizeof(T*) bytes, and then however many bytes it takes to
				// do the actual object. Things that are std::ref or plain T* are stored as 
				// just the sizeof(T*), and nothing else.
				T** pointerpointer = static_cast<T**>(lua_newuserdata(L, sizeof(T*) + sizeof(T)));
				T*& referencereference = *pointerpointer;
				T* allocationtarget = reinterpret_cast<T*>(pointerpointer + 1);
				referencereference = allocationtarget;
				std::allocator<T> alloc{};
				alloc.construct(allocationtarget, std::forward<Args>(args)...);
				f();
				return 1;
			}

			template <typename K, typename... Args>
			static int push_keyed(lua_State* L, K&& k, Args&&... args) {
				stack_detail::undefined_metatable<T> fx(L, &k[0]);
				return push_fx(L, fx, std::forward<Args>(args)...);
			}

			template <typename... Args>
			static int push(lua_State* L, Args&&... args) {
				return push_keyed(L, usertype_traits<T>::metatable(), std::forward<Args>(args)...);
			}
		};

		template <typename T>
		struct pusher<detail::as_pointer_tag<T>> {
			typedef meta::unqualified_t<T> U;

			template <typename F>
			static int push_fx(lua_State* L, F&& f, T* obj) {
				if (obj == nullptr)
					return stack::push(L, lua_nil);
				T** pref = static_cast<T**>(lua_newuserdata(L, sizeof(T*)));
				*pref = obj;
				f();
				return 1;
			}

			template <typename K>
			static int push_keyed(lua_State* L, K&& k, T* obj) {
				stack_detail::undefined_metatable<U*> fx(L, &k[0]);
				return push_fx(L, fx, obj);
			}

			static int push(lua_State* L, T* obj) {
				return push_keyed(L, usertype_traits<U*>::metatable(), obj);
			}
		};

		template <>
		struct pusher<detail::as_reference_tag> {
			template <typename T>
			static int push(lua_State* L, T&& obj) {
				return stack::push(L, detail::ptr(obj));
			}
		};

		template<typename T, typename>
		struct pusher {
			template <typename... Args>
			static int push(lua_State* L, Args&&... args) {
				return pusher<detail::as_value_tag<T>>{}.push(L, std::forward<Args>(args)...);
			}
		};
		
		template<typename T>
		struct pusher<T*, meta::disable_if_t<
			meta::any<
				is_container<meta::unqualified_t<T>>, 
				std::is_function<meta::unqualified_t<T>>,
				std::is_base_of<reference, meta::unqualified_t<T>>, 
				std::is_base_of<stack_reference, meta::unqualified_t<T>>
			>::value
		>> {
			template <typename... Args>
			static int push(lua_State* L, Args&&... args) {
				return pusher<detail::as_pointer_tag<T>>{}.push(L, std::forward<Args>(args)...);
			}
		};

		template<typename T>
		struct pusher<T, std::enable_if_t<is_unique_usertype<T>::value>> {
			typedef typename unique_usertype_traits<T>::type P;
			typedef typename unique_usertype_traits<T>::actual_type Real;

			template <typename Arg, meta::enable<std::is_base_of<Real, meta::unqualified_t<Arg>>> = meta::enabler>
			static int push(lua_State* L, Arg&& arg) {
				if (unique_usertype_traits<T>::is_null(arg)) {
					return stack::push(L, lua_nil);
				}
				return push_deep(L, std::forward<Arg>(arg));
			}

			template <typename Arg0, typename Arg1, typename... Args>
			static int push(lua_State* L, Arg0&& arg0, Arg0&& arg1, Args&&... args) {
				return push_deep(L, std::forward<Arg0>(arg0), std::forward<Arg1>(arg1), std::forward<Args>(args)...);
			}

			template <typename... Args>
			static int push_deep(lua_State* L, Args&&... args) {
				P** pref = static_cast<P**>(lua_newuserdata(L, sizeof(P*) + sizeof(detail::unique_destructor) + sizeof(Real)));
				detail::unique_destructor* fx = static_cast<detail::unique_destructor*>(static_cast<void*>(pref + 1));
				Real* mem = static_cast<Real*>(static_cast<void*>(fx + 1));
				*fx = detail::usertype_unique_alloc_destroy<P, Real>;
				detail::default_construct::construct(mem, std::forward<Args>(args)...);
				*pref = unique_usertype_traits<T>::get(*mem);
				if (luaL_newmetatable(L, &usertype_traits<detail::unique_usertype<P>>::metatable()[0]) == 1) {
					luaL_Reg l[32]{};
					int index = 0;
					auto prop_fx = [](meta_function) { return true; };
					usertype_detail::insert_default_registrations<P>(l, index, prop_fx);
					usertype_detail::make_destructor<T>(l, index);
					luaL_setfuncs(L, l, 0);
				}
				lua_setmetatable(L, -2);
				return 1;
			}
		};

		template<typename T>
		struct pusher<std::reference_wrapper<T>> {
			static int push(lua_State* L, const std::reference_wrapper<T>& t) {
				return stack::push(L, std::addressof(detail::deref(t.get())));
			}
		};

		template<typename T>
		struct pusher<T, std::enable_if_t<std::is_floating_point<T>::value>> {
			static int push(lua_State* L, const T& value) {
				lua_pushnumber(L, value);
				return 1;
			}
		};

		template<typename T>
		struct pusher<T, std::enable_if_t<std::is_integral<T>::value>> {
			static int push(lua_State* L, const T& value) {
#if SOL_LUA_VERSION >= 503
				static auto integer_value_fits = [](T const& value) {
					if (sizeof(T) < sizeof(lua_Integer) || (std::is_signed<T>::value && sizeof(T) == sizeof(lua_Integer))) {
						return true;
					}
					auto u_min = static_cast<std::intmax_t>((std::numeric_limits<lua_Integer>::min)());
					auto u_max = static_cast<std::uintmax_t>((std::numeric_limits<lua_Integer>::max)());
					auto t_min = static_cast<std::intmax_t>((std::numeric_limits<T>::min)());
					auto t_max = static_cast<std::uintmax_t>((std::numeric_limits<T>::max)());
					return (u_min <= t_min || value >= static_cast<T>(u_min)) && (u_max >= t_max || value <= static_cast<T>(u_max));
				};
				if (integer_value_fits(value)) {
					lua_pushinteger(L, static_cast<lua_Integer>(value));
					return 1;
				}
#endif
#if defined(SOL_CHECK_ARGUMENTS) && !defined(SOL_NO_CHECK_NUMBER_PRECISION)
				if (static_cast<T>(llround(static_cast<lua_Number>(value))) != value) {
#ifdef SOL_NO_EXCEPTIONS
					// Is this really worth it?
					assert(false && "integer value will be misrepresented in lua");
					lua_pushnumber(L, static_cast<lua_Number>(value));
					return 1;
#else
					throw error(detail::direct_error, "integer value will be misrepresented in lua");
#endif
				}
#endif
				lua_pushnumber(L, static_cast<lua_Number>(value));
				return 1;
			}
		};

		template<typename T>
		struct pusher<T, std::enable_if_t<std::is_enum<T>::value>> {
			static int push(lua_State* L, const T& value) {
				if (std::is_same<char, std::underlying_type_t<T>>::value) {
					return stack::push(L, static_cast<int>(value));
				}
				return stack::push(L, static_cast<std::underlying_type_t<T>>(value));
			}
		};

		template<typename T>
		struct pusher<as_table_t<T>, std::enable_if_t<is_container<std::remove_pointer_t<meta::unwrap_unqualified_t<T>>>::value>> {
			static int push(lua_State* L, const T& tablecont) {
				return push(meta::has_key_value_pair<meta::unqualified_t<std::remove_pointer_t<T>>>(), L, tablecont);
			}
			
			static int push(std::true_type, lua_State* L, const T& tablecont) {
				auto& cont = detail::deref(detail::unwrap(tablecont));
				lua_createtable(L, static_cast<int>(cont.size()), 0);
				int tableindex = lua_gettop(L);
				for (const auto& pair : cont) {
					set_field(L, pair.first, pair.second, tableindex);
				}
				return 1;
			}
			
			static int push(std::false_type, lua_State* L, const T& tablecont) {
				auto& cont = detail::deref(detail::unwrap(tablecont));
				lua_createtable(L, stack_detail::get_size_hint(cont), 0);
				int tableindex = lua_gettop(L);
				std::size_t index = 1;
				for (const auto& i : cont) {
#if SOL_LUA_VERSION >= 503
					int p = stack::push(L, i);
					for (int pi = 0; pi < p; ++pi) {
						lua_seti(L, tableindex, static_cast<lua_Integer>(index++));
					}
#else
					lua_pushinteger(L, static_cast<lua_Integer>(index));
					int p = stack::push(L, i);
					if (p == 1) {
						++index;
						lua_settable(L, tableindex);
					}
					else {
						int firstindex = tableindex + 1 + 1;
						for (int pi = 0; pi < p; ++pi) {
							stack::push(L, index);
							lua_pushvalue(L, firstindex);
							lua_settable(L, tableindex);
							++index;
							++firstindex;
						}
						lua_pop(L, 1 + p);
					}
#endif
				}
				// TODO: figure out a better way to do this...?
				//set_field(L, -1, cont.size());
				return 1;
			}
		};

		template<typename T>
		struct pusher<as_table_t<T>, std::enable_if_t<!is_container<std::remove_pointer_t<meta::unwrap_unqualified_t<T>>>::value>> {
			static int push(lua_State* L, const T& v) {
				return stack::push(L, v);
			}
		};

		template<typename T>
		struct pusher<nested<T>> {
			static int push(lua_State* L, const T& tablecont) {
				pusher<as_table_t<T>> p{};
				// silence annoying VC++ warning
				(void)p;
				return p.push(L, tablecont);
			}
		};

		template<typename T>
		struct pusher<T, std::enable_if_t<std::is_base_of<reference, T>::value || std::is_base_of<stack_reference, T>::value>> {
			static int push(lua_State* L, const T& ref) {
				return ref.push(L);
			}

			static int push(lua_State* L, T&& ref) {
				return ref.push(L);
			}
		};

		template<>
		struct pusher<bool> {
			static int push(lua_State* L, bool b) {
				lua_pushboolean(L, b);
				return 1;
			}
		};

		template<>
		struct pusher<lua_nil_t> {
			static int push(lua_State* L, lua_nil_t) {
				lua_pushnil(L);
				return 1;
			}
		};

		template<>
		struct pusher<stack_count> {
			static int push(lua_State*, stack_count st) {
				return st.count;
			}
		};

		template<>
		struct pusher<metatable_t> {
			static int push(lua_State* L, metatable_t) {
				lua_pushlstring(L, "__mt", 4);
				return 1;
			}
		};

		template<>
		struct pusher<std::remove_pointer_t<lua_CFunction>> {
			static int push(lua_State* L, lua_CFunction func, int n = 0) {
				lua_pushcclosure(L, func, n);
				return 1;
			}
		};

		template<>
		struct pusher<lua_CFunction> {
			static int push(lua_State* L, lua_CFunction func, int n = 0) {
				lua_pushcclosure(L, func, n);
				return 1;
			}
		};
#ifdef SOL_NOEXCEPT_FUNCTION_TYPE
		template<>
		struct pusher<std::remove_pointer_t<detail::lua_CFunction_noexcept>> {
			static int push(lua_State* L, detail::lua_CFunction_noexcept func, int n = 0) {
				lua_pushcclosure(L, func, n);
				return 1;
			}
		};

		template<>
		struct pusher<detail::lua_CFunction_noexcept> {
			static int push(lua_State* L, detail::lua_CFunction_noexcept func, int n = 0) {
				lua_pushcclosure(L, func, n);
				return 1;
			}
		};
#endif // noexcept function type

		template<>
		struct pusher<c_closure> {
			static int push(lua_State* L, c_closure cc) {
				lua_pushcclosure(L, cc.c_function, cc.upvalues);
				return 1;
			}
		};

		template<typename Arg, typename... Args>
		struct pusher<closure<Arg, Args...>> {
			template <std::size_t... I, typename T>
			static int push(std::index_sequence<I...>, lua_State* L, T&& c) {
				int pushcount = multi_push(L, detail::forward_get<I>(c.upvalues)...);
				return stack::push(L, c_closure(c.c_function, pushcount));
			}

			template <typename T>
			static int push(lua_State* L, T&& c) {
				return push(std::make_index_sequence<1 + sizeof...(Args)>(), L, std::forward<T>(c));
			}
		};

		template<>
		struct pusher<void*> {
			static int push(lua_State* L, void* userdata) {
				lua_pushlightuserdata(L, userdata);
				return 1;
			}
		};

		template<>
		struct pusher<lightuserdata_value> {
			static int push(lua_State* L, lightuserdata_value userdata) {
				lua_pushlightuserdata(L, userdata);
				return 1;
			}
		};

		template<typename T>
		struct pusher<light<T>> {
			static int push(lua_State* L, light<T> l) {
				lua_pushlightuserdata(L, static_cast<void*>(l.value));
				return 1;
			}
		};

		template<typename T>
		struct pusher<user<T>> {
			template <bool with_meta = true, typename Key, typename... Args>
			static int push_with(lua_State* L, Key&& name, Args&&... args) {
				// A dumb pusher
				void* rawdata = lua_newuserdata(L, sizeof(T));
				T* data = static_cast<T*>(rawdata);
				std::allocator<T> alloc;
				alloc.construct(data, std::forward<Args>(args)...);
				if (with_meta) {
					lua_CFunction cdel = detail::user_alloc_destruct<T>;
					// Make sure we have a plain GC set for this data
					if (luaL_newmetatable(L, name) != 0) {
						lua_pushcclosure(L, cdel, 0);
						lua_setfield(L, -2, "__gc");
					}
					lua_setmetatable(L, -2);
				}
				return 1;
			}

			template <typename Arg, typename... Args, meta::disable<meta::any_same<meta::unqualified_t<Arg>, no_metatable_t, metatable_t>> = meta::enabler>
			static int push(lua_State* L, Arg&& arg, Args&&... args) {
				const auto name = &usertype_traits<meta::unqualified_t<T>>::user_gc_metatable()[0];
				return push_with(L, name, std::forward<Arg>(arg), std::forward<Args>(args)...);
			}

			template <typename... Args>
			static int push(lua_State* L, no_metatable_t, Args&&... args) {
				const auto name = &usertype_traits<meta::unqualified_t<T>>::user_gc_metatable()[0];
				return push_with<false>(L, name, std::forward<Args>(args)...);
			}

			template <typename Key, typename... Args>
			static int push(lua_State* L, metatable_t, Key&& key, Args&&... args) {
				const auto name = &key[0];
				return push_with<true>(L, name, std::forward<Args>(args)...);
			}

			static int push(lua_State* L, const user<T>& u) {
				const auto name = &usertype_traits<meta::unqualified_t<T>>::user_gc_metatable()[0];
				return push_with(L, name, u.value);
			}

			static int push(lua_State* L, user<T>&& u) {
				const auto name = &usertype_traits<meta::unqualified_t<T>>::user_gc_metatable()[0];
				return push_with(L, name, std::move(u.value));
			}

			static int push(lua_State* L, no_metatable_t, const user<T>& u) {
				const auto name = &usertype_traits<meta::unqualified_t<T>>::user_gc_metatable()[0];
				return push_with<false>(L, name, u.value);
			}

			static int push(lua_State* L, no_metatable_t, user<T>&& u) {
				const auto name = &usertype_traits<meta::unqualified_t<T>>::user_gc_metatable()[0];
				return push_with<false>(L, name, std::move(u.value));
			}
		};

		template<>
		struct pusher<userdata_value> {
			static int push(lua_State* L, userdata_value data) {
				void** ud = static_cast<void**>(lua_newuserdata(L, sizeof(void*)));
				*ud = data.value;
				return 1;
			}
		};

		template<>
		struct pusher<const char*> {
			static int push_sized(lua_State* L, const char* str, std::size_t len) {
				lua_pushlstring(L, str, len);
				return 1;
			}

			static int push(lua_State* L, const char* str) {
				if (str == nullptr)
					return stack::push(L, lua_nil);
				return push_sized(L, str, std::char_traits<char>::length(str));
			}

			static int push(lua_State* L, const char* strb, const char* stre) {
				return push_sized(L, strb, stre - strb);
			}

			static int push(lua_State* L, const char* str, std::size_t len) {
				return push_sized(L, str, len);
			}
		};

		template<size_t N>
		struct pusher<char[N]> {
			static int push(lua_State* L, const char(&str)[N]) {
				lua_pushlstring(L, str, N - 1);
				return 1;
			}

			static int push(lua_State* L, const char(&str)[N], std::size_t sz) {
				lua_pushlstring(L, str, sz);
				return 1;
			}
		};

		template <>
		struct pusher<char> {
			static int push(lua_State* L, char c) {
				const char str[2] = { c, '\0' };
				return stack::push(L, str, 1);
			}
		};

		template<>
		struct pusher<std::string> {
			static int push(lua_State* L, const std::string& str) {
				lua_pushlstring(L, str.c_str(), str.size());
				return 1;
			}

			static int push(lua_State* L, const std::string& str, std::size_t sz) {
				lua_pushlstring(L, str.c_str(), sz);
				return 1;
			}
		};

		template <>
		struct pusher<string_view> {
			static int push(lua_State* L, const string_view& sv) {
				return stack::push(L, sv.data(), sv.length());
			}

			static int push(lua_State* L, const string_view& sv, std::size_t n) {
				return stack::push(L, sv.data(), n);
			}
		};

		template<>
		struct pusher<meta_function> {
			static int push(lua_State* L, meta_function m) {
				const std::string& str = to_string(m);
				lua_pushlstring(L, str.c_str(), str.size());
				return 1;
			}
		};

		template <>
		struct pusher<absolute_index> {
			static int push(lua_State* L, absolute_index ai) {
				lua_pushvalue(L, ai);
				return 1;
			}
		};

		template <>
		struct pusher<raw_index> {
			static int push(lua_State* L, raw_index ri) {
				lua_pushvalue(L, ri);
				return 1;
			}
		};

		template <>
		struct pusher<ref_index> {
			static int push(lua_State* L, ref_index ri) {
				lua_rawgeti(L, LUA_REGISTRYINDEX, ri);
				return 1;
			}
		};

#ifdef SOL_CODECVT_SUPPORT
		template<>
		struct pusher<const wchar_t*> {
			static int push(lua_State* L, const wchar_t* wstr) {
				return push(L, wstr, std::char_traits<wchar_t>::length(wstr));
			}

			static int push(lua_State* L, const wchar_t* wstr, std::size_t sz) {
				return push(L, wstr, wstr + sz);
			}

			static int push(lua_State* L, const wchar_t* strb, const wchar_t* stre) {
				if (sizeof(wchar_t) == 2) {
					thread_local std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> convert;
					std::string u8str = convert.to_bytes(strb, stre);
					return stack::push(L, u8str);
				}
				thread_local std::wstring_convert<std::codecvt_utf8<wchar_t>> convert;
				std::string u8str = convert.to_bytes(strb, stre);
				return stack::push(L, u8str);
			}
		};

		template<>
		struct pusher<const char16_t*> {
			static int push(lua_State* L, const char16_t* u16str) {
				return push(L, u16str, std::char_traits<char16_t>::length(u16str));
			}

			static int push(lua_State* L, const char16_t* u16str, std::size_t sz) {
				return push(L, u16str, u16str + sz);
			}

			static int push(lua_State* L, const char16_t* strb, const char16_t* stre) {
#ifdef _MSC_VER
				thread_local std::wstring_convert<std::codecvt_utf8_utf16<int16_t>, int16_t> convert;
				std::string u8str = convert.to_bytes(reinterpret_cast<const int16_t*>(strb), reinterpret_cast<const int16_t*>(stre));
#else
				thread_local std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t> convert;
				std::string u8str = convert.to_bytes(strb, stre);
#endif // VC++ is a shit
				return stack::push(L, u8str);
			}
		};

		template<>
		struct pusher<const char32_t*> {
			static int push(lua_State* L, const char32_t* u32str) {
				return push(L, u32str, u32str + std::char_traits<char32_t>::length(u32str));
			}

			static int push(lua_State* L, const char32_t* u32str, std::size_t sz) {
				return push(L, u32str, u32str + sz);
			}

			static int push(lua_State* L, const char32_t* strb, const char32_t* stre) {
#ifdef _MSC_VER
				thread_local std::wstring_convert<std::codecvt_utf8<int32_t>, int32_t> convert;
				std::string u8str = convert.to_bytes(reinterpret_cast<const int32_t*>(strb), reinterpret_cast<const int32_t*>(stre));
#else
				thread_local std::wstring_convert<std::codecvt_utf8<char32_t>, char32_t> convert;
				std::string u8str = convert.to_bytes(strb, stre);
#endif // VC++ is a shit
				return stack::push(L, u8str);
			}
		};

		template<size_t N>
		struct pusher<wchar_t[N]> {
			static int push(lua_State* L, const wchar_t(&str)[N]) {
				return push(L, str, N - 1);
			}

			static int push(lua_State* L, const wchar_t(&str)[N], std::size_t sz) {
				return stack::push<const wchar_t*>(L, str, str + sz);
			}
		};

		template<size_t N>
		struct pusher<char16_t[N]> {
			static int push(lua_State* L, const char16_t(&str)[N]) {
				return push(L, str, N - 1);
			}

			static int push(lua_State* L, const char16_t(&str)[N], std::size_t sz) {
				return stack::push<const char16_t*>(L, str, str + sz);
			}
		};

		template<size_t N>
		struct pusher<char32_t[N]> {
			static int push(lua_State* L, const char32_t(&str)[N]) {
				return push(L, str, N - 1);
			}

			static int push(lua_State* L, const char32_t(&str)[N], std::size_t sz) {
				return stack::push<const char32_t*>(L, str, str + sz);
			}
		};

		template <>
		struct pusher<wchar_t> {
			static int push(lua_State* L, wchar_t c) {
				const wchar_t str[2] = { c, '\0' };
				return stack::push(L, str, 1);
			}
		};

		template <>
		struct pusher<char16_t> {
			static int push(lua_State* L, char16_t c) {
				const char16_t str[2] = { c, '\0' };
				return stack::push(L, str, 1);
			}
		};

		template <>
		struct pusher<char32_t> {
			static int push(lua_State* L, char32_t c) {
				const char32_t str[2] = { c, '\0' };
				return stack::push(L, str, 1);
			}
		};

		template<>
		struct pusher<std::wstring> {
			static int push(lua_State* L, const std::wstring& wstr) {
				return push(L, wstr.data(), wstr.size());
			}

			static int push(lua_State* L, const std::wstring& wstr, std::size_t sz) {
				return stack::push(L, wstr.data(), wstr.data() + sz);
			}
		};

		template<>
		struct pusher<std::u16string> {
			static int push(lua_State* L, const std::u16string& u16str) {
				return push(L, u16str, u16str.size());
			}
			
			static int push(lua_State* L, const std::u16string& u16str, std::size_t sz) {
				return stack::push(L, u16str.data(), u16str.data() + sz);
			}
		};

		template<>
		struct pusher<std::u32string> {
			static int push(lua_State* L, const std::u32string& u32str) {
				return push(L, u32str, u32str.size());
			}

			static int push(lua_State* L, const std::u32string& u32str, std::size_t sz) {
				return stack::push(L, u32str.data(), u32str.data() + sz);
			}
		};

		template <>
		struct pusher<wstring_view> {
			static int push(lua_State* L, const wstring_view& sv) {
				return stack::push(L, sv.data(), sv.length());
			}

			static int push(lua_State* L, const wstring_view& sv, std::size_t n) {
				return stack::push(L, sv.data(), n);
			}
		};

		template <>
		struct pusher<u16string_view> {
			static int push(lua_State* L, const u16string_view& sv) {
				return stack::push(L, sv.data(), sv.length());
			}

			static int push(lua_State* L, const u16string_view& sv, std::size_t n) {
				return stack::push(L, sv.data(), n);
			}
		};

		template <>
		struct pusher<u32string_view> {
			static int push(lua_State* L, const u32string_view& sv) {
				return stack::push(L, sv.data(), sv.length());
			}

			static int push(lua_State* L, const u32string_view& sv, std::size_t n) {
				return stack::push(L, sv.data(), n);
			}
		};
#endif // codecvt Header Support

		template<typename... Args>
		struct pusher<std::tuple<Args...>> {
			template <std::size_t... I, typename T>
			static int push(std::index_sequence<I...>, lua_State* L, T&& t) {
				int pushcount = 0;
				(void)detail::swallow{ 0, (pushcount += stack::push(L,
					  detail::forward_get<I>(t)
				), 0)... };
				return pushcount;
			}

			template <typename T>
			static int push(lua_State* L, T&& t) {
				return push(std::index_sequence_for<Args...>(), L, std::forward<T>(t));
			}
		};

		template<typename A, typename B>
		struct pusher<std::pair<A, B>> {
			template <typename T>
			static int push(lua_State* L, T&& t) {
				int pushcount = stack::push(L, detail::forward_get<0>(t));
				pushcount += stack::push(L, detail::forward_get<1>(t));
				return pushcount;
			}
		};

		template<typename O>
		struct pusher<optional<O>> {
			template <typename T>
			static int push(lua_State* L, T&& t) {
				if (t == nullopt) {
					return stack::push(L, nullopt);
				}
				return stack::push(L, static_cast<std::conditional_t<std::is_lvalue_reference<T>::value, O&, O&&>>(t.value()));
			}
		};

		template<>
		struct pusher<nullopt_t> {
			static int push(lua_State* L, nullopt_t) {
				return stack::push(L, lua_nil);
			}
		};

		template<>
		struct pusher<std::nullptr_t> {
			static int push(lua_State* L, std::nullptr_t) {
				return stack::push(L, lua_nil);
			}
		};

		template<>
		struct pusher<this_state> {
			static int push(lua_State*, const this_state&) {
				return 0;
			}
		};

		template<>
		struct pusher<new_table> {
			static int push(lua_State* L, const new_table& nt) {
				lua_createtable(L, nt.sequence_hint, nt.map_hint);
				return 1;
			}
		};

#ifdef SOL_CXX17_FEATURES
		namespace stack_detail {

			struct push_function {
				lua_State* L;

				push_function(lua_State* L) : L(L) {}

				template <typename T>
				int operator()(T&& value) const {
					return stack::push<T>(L, std::forward<T>(value));
				}
			};

		} // stack_detail

		template <typename... Tn>
		struct pusher<std::variant<Tn...>> {
			static int push(lua_State* L, const std::variant<Tn...>& v) {
				return std::visit(stack_detail::push_function(L), v);
			}

			static int push(lua_State* L, std::variant<Tn...>&& v) {
				return std::visit(stack_detail::push_function(L), std::move(v));
			}
		};
#endif // C++17 Support


	} // stack
} // sol

#endif // SOL_STACK_PUSH_HPP