sol2/include/sol/stack_core.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_STACK_CORE_HPP
#define SOL_STACK_CORE_HPP

#include <sol/types.hpp>
#include <sol/inheritance.hpp>
#include <sol/error_handler.hpp>
#include <sol/reference.hpp>
#include <sol/stack_reference.hpp>
#include <sol/tuple.hpp>
#include <sol/traits.hpp>
#include <sol/tie.hpp>
#include <sol/stack_guard.hpp>
#include <sol/demangle.hpp>
#include <sol/forward_detail.hpp>

#include <vector>
#include <bitset>
#include <forward_list>
#include <string>
#include <limits>
#include <algorithm>
#include <sstream>
#include <optional>
#include <type_traits>

namespace sol {
	namespace detail {
		struct with_function_tag { };
		struct as_reference_tag { };
		template <typename T>
		struct as_pointer_tag { };
		template <typename T>
		struct as_value_tag { };
		template <typename T>
		struct as_unique_tag { };
		template <typename T>
		struct as_table_tag { };

		template <typename Tag>
		inline constexpr bool is_tagged_v
		     = meta::is_specialization_of_v<Tag,
		            detail::
		                 as_pointer_tag> || meta::is_specialization_of_v<Tag, as_value_tag> || meta::is_specialization_of_v<Tag, as_unique_tag> || meta::is_specialization_of_v<Tag, as_table_tag> || std::is_same_v<Tag, as_reference_tag> || std::is_same_v<Tag, with_function_tag>;

		using lua_reg_table = luaL_Reg[64];

		using unique_destructor = void (*)(void*);
		using unique_tag = detail::inheritance_unique_cast_function;

		inline void* alloc_newuserdata(lua_State* L, std::size_t bytesize) {
#if SOL_LUA_VERSION_I_ >= 504
			return lua_newuserdatauv(L, bytesize, 1);
#else
			return lua_newuserdata(L, bytesize);
#endif
		}

		constexpr std::uintptr_t align(std::size_t alignment, std::uintptr_t ptr, std::size_t& space) {
			// this handles arbitrary alignments...
			// make this into a power-of-2-only?
			// actually can't: this is a C++14-compatible framework,
			// power of 2 alignment is C++17
			std::uintptr_t offby = static_cast<std::uintptr_t>(ptr % alignment);
			std::uintptr_t padding = (alignment - offby) % alignment;
			ptr += padding;
			space -= padding;
			return ptr;
		}

		inline void* align(std::size_t alignment, void* ptr, std::size_t& space) {
			return reinterpret_cast<void*>(align(alignment, reinterpret_cast<std::uintptr_t>(ptr), space));
		}

		constexpr std::uintptr_t align_one(std::size_t alignment, std::size_t size, std::uintptr_t ptr) {
			std::size_t space = (std::numeric_limits<std::size_t>::max)();
			return align(alignment, ptr, space) + size;
		}

		template <typename... Args>
		constexpr std::size_t aligned_space_for(std::uintptr_t ptr) {
			std::uintptr_t end = ptr;
			((end = align_one(alignof(Args), sizeof(Args), end)), ...);
			return static_cast<std::size_t>(end - ptr);
		}

		template <typename... Args>
		constexpr std::size_t aligned_space_for() {
			static_assert(sizeof...(Args) > 0);

			constexpr std::size_t max_arg_alignment = (std::max)({ alignof(Args)... });
			if constexpr (max_arg_alignment <= alignof(std::max_align_t)) {
				// If all types are `good enough`, simply calculate alignment in case of the worst allocator
				std::size_t worst_required_size = 0;
				for (std::size_t ptr = 0; ptr < max_arg_alignment; ptr++) {
					worst_required_size = (std::max)(worst_required_size, aligned_space_for<Args...>(ptr));
				}
				return worst_required_size;
			}
			else {
				// For over-aligned types let's assume that every Arg in Args starts at the worst aligned address
				return (aligned_space_for<Args>(0x1) + ...);
			}
		}

		inline void* align_usertype_pointer(void* ptr) {
			using use_align = std::integral_constant<bool,
#if SOL_IS_OFF(SOL_ALIGN_MEMORY)
			     false
#else
			     (std::alignment_of<void*>::value > 1)
#endif
			     >;
			if (!use_align::value) {
				return ptr;
			}
			std::size_t space = (std::numeric_limits<std::size_t>::max)();
			return align(std::alignment_of<void*>::value, ptr, space);
		}

		template <bool pre_aligned = false, bool pre_shifted = false>
		void* align_usertype_unique_destructor(void* ptr) {
			using use_align = std::integral_constant<bool,
#if SOL_IS_OFF(SOL_ALIGN_MEMORY)
			     false
#else
			     (std::alignment_of<unique_destructor>::value > 1)
#endif
			     >;
			if (!pre_aligned) {
				ptr = align_usertype_pointer(ptr);
			}
			if (!pre_shifted) {
				ptr = static_cast<void*>(static_cast<char*>(ptr) + sizeof(void*));
			}
			if (!use_align::value) {
				return static_cast<void*>(static_cast<void**>(ptr) + 1);
			}
			std::size_t space = (std::numeric_limits<std::size_t>::max)();
			return align(std::alignment_of<unique_destructor>::value, ptr, space);
		}

		template <bool pre_aligned = false, bool pre_shifted = false>
		void* align_usertype_unique_tag(void* ptr) {
			using use_align = std::integral_constant<bool,
#if SOL_IS_OFF(SOL_ALIGN_MEMORY)
			     false
#else
			     (std::alignment_of<unique_tag>::value > 1)
#endif
			     >;
			if (!pre_aligned) {
				ptr = align_usertype_unique_destructor(ptr);
			}
			if (!pre_shifted) {
				ptr = static_cast<void*>(static_cast<char*>(ptr) + sizeof(unique_destructor));
			}
			if (!use_align::value) {
				return ptr;
			}
			std::size_t space = (std::numeric_limits<std::size_t>::max)();
			return align(std::alignment_of<unique_tag>::value, ptr, space);
		}

		template <typename T, bool pre_aligned = false, bool pre_shifted = false>
		void* align_usertype_unique(void* ptr) {
			typedef std::integral_constant<bool,
#if SOL_IS_OFF(SOL_ALIGN_MEMORY)
			     false
#else
			     (std::alignment_of_v<T> > 1)
#endif
			     >
			     use_align;
			if (!pre_aligned) {
				ptr = align_usertype_unique_tag(ptr);
			}
			if (!pre_shifted) {
				ptr = static_cast<void*>(static_cast<char*>(ptr) + sizeof(unique_tag));
			}
			if (!use_align::value) {
				return ptr;
			}
			std::size_t space = (std::numeric_limits<std::size_t>::max)();
			return align(std::alignment_of_v<T>, ptr, space);
		}

		template <typename T>
		void* align_user(void* ptr) {
			typedef std::integral_constant<bool,
#if SOL_IS_OFF(SOL_ALIGN_MEMORY)
			     false
#else
			     (std::alignment_of_v<T> > 1)
#endif
			     >
			     use_align;
			if (!use_align::value) {
				return ptr;
			}
			std::size_t space = (std::numeric_limits<std::size_t>::max)();
			return align(std::alignment_of_v<T>, ptr, space);
		}

		template <typename T>
		T** usertype_allocate_pointer(lua_State* L) {
			typedef std::integral_constant<bool,
#if SOL_IS_OFF(SOL_ALIGN_MEMORY)
			     false
#else
			     (std::alignment_of<T*>::value > 1)
#endif
			     >
			     use_align;
			if (!use_align::value) {
				T** pointerpointer = static_cast<T**>(alloc_newuserdata(L, sizeof(T*)));
				return pointerpointer;
			}
			constexpr std::size_t initial_size = aligned_space_for<T*>();

			std::size_t allocated_size = initial_size;
			void* unadjusted = alloc_newuserdata(L, initial_size);
			void* adjusted = align(std::alignment_of<T*>::value, unadjusted, allocated_size);
			if (adjusted == nullptr) {
				// trash allocator can burn in hell
				lua_pop(L, 1);
				// luaL_error(L, "if you are the one that wrote this allocator you should feel bad for doing a
				// worse job than malloc/realloc and should go read some books, yeah?");
				luaL_error(L, "cannot properly align memory for '%s'", detail::demangle<T*>().data());
			}
			return static_cast<T**>(adjusted);
		}

		inline bool attempt_alloc(lua_State* L, std::size_t ptr_align, std::size_t ptr_size, std::size_t value_align,
		     std::size_t allocated_size, void*& pointer_adjusted, void*& data_adjusted) {
			void* adjusted = alloc_newuserdata(L, allocated_size);
			pointer_adjusted = align(ptr_align, adjusted, allocated_size);
			if (pointer_adjusted == nullptr) {
				lua_pop(L, 1);
				return false;
			}
			// subtract size of what we're going to allocate there
			allocated_size -= ptr_size;
			adjusted = static_cast<void*>(static_cast<char*>(pointer_adjusted) + ptr_size);
			data_adjusted = align(value_align, adjusted, allocated_size);
			if (data_adjusted == nullptr) {
				lua_pop(L, 1);
				return false;
			}
			return true;
		}

		inline bool attempt_alloc_unique(lua_State* L, std::size_t ptr_align, std::size_t ptr_size, std::size_t real_align,
		     std::size_t allocated_size, void*& pointer_adjusted, void*& dx_adjusted, void*& id_adjusted, void*& data_adjusted) {
			void* adjusted = alloc_newuserdata(L, allocated_size);
			pointer_adjusted = align(ptr_align, adjusted, allocated_size);
			if (pointer_adjusted == nullptr) {
				lua_pop(L, 1);
				return false;
			}
			allocated_size -= ptr_size;

			adjusted = static_cast<void*>(static_cast<char*>(pointer_adjusted) + ptr_size);
			dx_adjusted = align(std::alignment_of_v<unique_destructor>, adjusted, allocated_size);
			if (dx_adjusted == nullptr) {
				lua_pop(L, 1);
				return false;
			}
			allocated_size -= sizeof(unique_destructor);

			adjusted = static_cast<void*>(static_cast<char*>(dx_adjusted) + sizeof(unique_destructor));

			id_adjusted = align(std::alignment_of_v<unique_tag>, adjusted, allocated_size);
			if (id_adjusted == nullptr) {
				lua_pop(L, 1);
				return false;
			}
			allocated_size -= sizeof(unique_tag);

			adjusted = static_cast<void*>(static_cast<char*>(id_adjusted) + sizeof(unique_tag));
			data_adjusted = align(real_align, adjusted, allocated_size);
			if (data_adjusted == nullptr) {
				lua_pop(L, 1);
				return false;
			}
			return true;
		}

		template <typename T>
		T* usertype_allocate(lua_State* L) {
			typedef std::integral_constant<bool,
#if SOL_IS_OFF(SOL_ALIGN_MEMORY)
			     false
#else
			     (std::alignment_of<T*>::value > 1 || std::alignment_of_v<T> > 1)
#endif
			     >
			     use_align;
			if (!use_align::value) {
				T** pointerpointer = static_cast<T**>(alloc_newuserdata(L, sizeof(T*) + sizeof(T)));
				T*& pointerreference = *pointerpointer;
				T* allocationtarget = reinterpret_cast<T*>(pointerpointer + 1);
				pointerreference = allocationtarget;
				return allocationtarget;
			}

			constexpr std::size_t initial_size = aligned_space_for<T*, T>();

			void* pointer_adjusted;
			void* data_adjusted;
			bool result
			     = attempt_alloc(L, std::alignment_of_v<T*>, sizeof(T*), std::alignment_of_v<T>, initial_size, pointer_adjusted, data_adjusted);
			if (!result) {
				if (pointer_adjusted == nullptr) {
					luaL_error(L, "aligned allocation of userdata block (pointer section) for '%s' failed", detail::demangle<T>().c_str());
				}
				else {
					luaL_error(L, "aligned allocation of userdata block (data section) for '%s' failed", detail::demangle<T>().c_str());
				}
				return nullptr;
			}

			T** pointerpointer = reinterpret_cast<T**>(pointer_adjusted);
			T*& pointerreference = *pointerpointer;
			T* allocationtarget = reinterpret_cast<T*>(data_adjusted);
			pointerreference = allocationtarget;
			return allocationtarget;
		}

		template <typename T, typename Real>
		Real* usertype_unique_allocate(lua_State* L, T**& pref, unique_destructor*& dx, unique_tag*& id) {
			typedef std::integral_constant<bool,
#if SOL_IS_OFF(SOL_ALIGN_MEMORY)
			     false
#else
			     (std::alignment_of<T*>::value > 1 || std::alignment_of<unique_tag>::value > 1 || std::alignment_of<unique_destructor>::value > 1
			          || std::alignment_of<Real>::value > 1)
#endif
			     >
			     use_align;
			if (!use_align::value) {
				pref = static_cast<T**>(alloc_newuserdata(L, sizeof(T*) + sizeof(detail::unique_destructor) + sizeof(unique_tag) + sizeof(Real)));
				dx = static_cast<detail::unique_destructor*>(static_cast<void*>(pref + 1));
				id = static_cast<unique_tag*>(static_cast<void*>(dx + 1));
				Real* mem = static_cast<Real*>(static_cast<void*>(id + 1));
				return mem;
			}

			constexpr std::size_t initial_size = aligned_space_for<T*, unique_destructor, unique_tag, Real>();

			void* pointer_adjusted;
			void* dx_adjusted;
			void* id_adjusted;
			void* data_adjusted;
			bool result = attempt_alloc_unique(L,
			     std::alignment_of_v<T*>,
			     sizeof(T*),
			     std::alignment_of_v<Real>,
			     initial_size,
			     pointer_adjusted,
			     dx_adjusted,
			     id_adjusted,
			     data_adjusted);
			if (!result) {
				if (pointer_adjusted == nullptr) {
					luaL_error(L, "aligned allocation of userdata block (pointer section) for '%s' failed", detail::demangle<T>().c_str());
				}
				else if (dx_adjusted == nullptr) {
					luaL_error(L, "aligned allocation of userdata block (deleter section) for '%s' failed", detail::demangle<T>().c_str());
				}
				else {
					luaL_error(L, "aligned allocation of userdata block (data section) for '%s' failed", detail::demangle<T>().c_str());
				}
				return nullptr;
			}

			pref = static_cast<T**>(pointer_adjusted);
			dx = static_cast<detail::unique_destructor*>(dx_adjusted);
			id = static_cast<unique_tag*>(id_adjusted);
			Real* mem = static_cast<Real*>(data_adjusted);
			return mem;
		}

		template <typename T>
		T* user_allocate(lua_State* L) {
			typedef std::integral_constant<bool,
#if SOL_IS_OFF(SOL_ALIGN_MEMORY)
			     false
#else
			     (std::alignment_of_v<T> > 1)
#endif
			     >
			     use_align;
			if (!use_align::value) {
				T* pointer = static_cast<T*>(alloc_newuserdata(L, sizeof(T)));
				return pointer;
			}

			constexpr std::size_t initial_size = aligned_space_for<T>();

			std::size_t allocated_size = initial_size;
			void* unadjusted = alloc_newuserdata(L, allocated_size);
			void* adjusted = align(std::alignment_of_v<T>, unadjusted, allocated_size);
			if (adjusted == nullptr) {
				lua_pop(L, 1);
				luaL_error(L, "cannot properly align memory for '%s'", detail::demangle<T>().data());
			}
			return static_cast<T*>(adjusted);
		}

		template <typename T>
		int usertype_alloc_destroy(lua_State* L) noexcept {
			void* memory = lua_touserdata(L, 1);
			memory = align_usertype_pointer(memory);
			T** pdata = static_cast<T**>(memory);
			T* data = *pdata;
			std::allocator<T> alloc {};
			std::allocator_traits<std::allocator<T>>::destroy(alloc, data);
			return 0;
		}

		template <typename T>
		int unique_destroy(lua_State* L) noexcept {
			void* memory = lua_touserdata(L, 1);
			memory = align_usertype_unique_destructor(memory);
			unique_destructor& dx = *static_cast<unique_destructor*>(memory);
			memory = align_usertype_unique_tag<true>(memory);
			(dx)(memory);
			return 0;
		}

		template <typename T>
		int user_alloc_destroy(lua_State* L) noexcept {
			void* memory = lua_touserdata(L, 1);
			void* aligned_memory = align_user<T>(memory);
			T* typed_memory = static_cast<T*>(aligned_memory);
			std::allocator<T> alloc;
			std::allocator_traits<std::allocator<T>>::destroy(alloc, typed_memory);
			return 0;
		}

		template <typename T, typename Real>
		void usertype_unique_alloc_destroy(void* memory) {
			void* aligned_memory = align_usertype_unique<Real, true>(memory);
			Real* typed_memory = static_cast<Real*>(aligned_memory);
			std::allocator<Real> alloc;
			std::allocator_traits<std::allocator<Real>>::destroy(alloc, typed_memory);
		}

		template <typename T>
		int cannot_destroy(lua_State* L) {
			return luaL_error(L,
			     "cannot call the destructor for '%s': it is either hidden (protected/private) or removed with '= "
			     "delete' and thusly this type is being destroyed without properly destroying, invoking undefined "
			     "behavior: please bind a usertype and specify a custom destructor to define the behavior properly",
			     detail::demangle<T>().data());
		}

		template <typename T>
		void reserve(T&, std::size_t) {
		}

		template <typename T, typename Al>
		void reserve(std::vector<T, Al>& vec, std::size_t hint) {
			vec.reserve(hint);
		}

		template <typename T, typename Tr, typename Al>
		void reserve(std::basic_string<T, Tr, Al>& str, std::size_t hint) {
			str.reserve(hint);
		}

		inline bool property_always_true(meta_function) {
			return true;
		}

		struct properties_enrollment_allowed {
			int& times_through;
			std::bitset<64>& properties;
			automagic_enrollments& enrollments;

			properties_enrollment_allowed(int& times_through_, std::bitset<64>& properties_, automagic_enrollments& enrollments_)
			: times_through(times_through_), properties(properties_), enrollments(enrollments_) {
			}

			bool operator()(meta_function mf) const {
				bool p = properties[static_cast<std::size_t>(mf)];
				if (times_through > 0) {
					return p;
				}
				switch (mf) {
				case meta_function::length:
					return enrollments.length_operator && !p;
				case meta_function::pairs:
					return enrollments.pairs_operator && !p;
				case meta_function::call:
					return enrollments.call_operator && !p;
				case meta_function::less_than:
					return enrollments.less_than_operator && !p;
				case meta_function::less_than_or_equal_to:
					return enrollments.less_than_or_equal_to_operator && !p;
				case meta_function::equal_to:
					return enrollments.equal_to_operator && !p;
				default:
					break;
				}
				return !p;
			}
		};

		struct indexed_insert {
			lua_reg_table& registration_table;
			int& index;

			indexed_insert(lua_reg_table& registration_table_, int& index_ref_) : registration_table(registration_table_), index(index_ref_) {
			}
			void operator()(meta_function meta_function_name_, lua_CFunction c_function_) {
				registration_table[index] = luaL_Reg { to_string(meta_function_name_).c_str(), c_function_ };
				++index;
			}
		};
	} // namespace detail

	namespace stack {

		template <typename T, bool global = false, bool raw = false, typename = void>
		struct field_getter;
		template <typename T, typename P, bool global = false, bool raw = false, typename = void>
		struct probe_field_getter;

		template <typename T, bool global = false, bool raw = false, typename = void>
		struct field_setter;

		template <typename T, typename = void>
		struct unqualified_getter;
		template <typename T, typename = void>
		struct qualified_getter;

		template <typename T, typename = void>
		struct qualified_interop_getter;
		template <typename T, typename = void>
		struct unqualified_interop_getter;

		template <typename T, typename = void>
		struct popper;

		template <typename T, typename = void>
		struct unqualified_pusher;

		template <typename T, type t, typename = void>
		struct unqualified_checker;
		template <typename T, type t, typename = void>
		struct qualified_checker;

		template <typename T, typename = void>
		struct unqualified_check_getter;
		template <typename T, typename = void>
		struct qualified_check_getter;

		struct probe {
			bool success;
			int levels;

			probe(bool s, int l) : success(s), levels(l) {
			}

			operator bool() const {
				return success;
			};
		};

		struct record {
			int last;
			int used;

			record() noexcept : last(), used() {
			}
			void use(int count) noexcept {
				last = count;
				used += count;
			}
		};

		namespace stack_detail {
			template <typename Function>
			Function* get_function_pointer(lua_State*, int, record&) noexcept;
			template <typename Function, typename Handler>
			bool check_function_pointer(lua_State* L, int index, Handler&& handler, record& tracking) noexcept;
		} // namespace stack_detail

	} // namespace stack

	namespace meta { namespace meta_detail {
		template <typename T>
		using adl_sol_lua_get_test_t = decltype(sol_lua_get(types<T>(), static_cast<lua_State*>(nullptr), -1, std::declval<stack::record&>()));

		template <typename T>
		using adl_sol_lua_interop_get_test_t
			= decltype(sol_lua_interop_get(types<T>(), static_cast<lua_State*>(nullptr), -1, static_cast<void*>(nullptr), std::declval<stack::record&>()));

		template <typename T>
		using adl_sol_lua_check_test_t = decltype(sol_lua_check(types<T>(), static_cast<lua_State*>(nullptr), -1, &no_panic, std::declval<stack::record&>()));

		template <typename T>
		using adl_sol_lua_interop_check_test_t
			= decltype(sol_lua_interop_check(types<T>(), static_cast<lua_State*>(nullptr), -1, type::none, &no_panic, std::declval<stack::record&>()));

		template <typename T>
		using adl_sol_lua_check_get_test_t
			= decltype(sol_lua_check_get(types<T>(), static_cast<lua_State*>(nullptr), -1, &no_panic, std::declval<stack::record&>()));

		template <typename... Args>
		using adl_sol_lua_push_test_t = decltype(sol_lua_push(static_cast<lua_State*>(nullptr), std::declval<Args>()...));

		template <typename T, typename... Args>
		using adl_sol_lua_push_exact_test_t = decltype(sol_lua_push(types<T>(), static_cast<lua_State*>(nullptr), std::declval<Args>()...));

		template <typename T>
		inline constexpr bool is_adl_sol_lua_get_v = meta::is_detected_v<adl_sol_lua_get_test_t, T>;

		template <typename T>
		inline constexpr bool is_adl_sol_lua_interop_get_v = meta::is_detected_v<adl_sol_lua_interop_get_test_t, T>;

		template <typename T>
		inline constexpr bool is_adl_sol_lua_check_v = meta::is_detected_v<adl_sol_lua_check_test_t, T>;

		template <typename T>
		inline constexpr bool is_adl_sol_lua_interop_check_v = meta::is_detected_v<adl_sol_lua_interop_check_test_t, T>;

		template <typename T>
		inline constexpr bool is_adl_sol_lua_check_get_v = meta::is_detected_v<adl_sol_lua_check_get_test_t, T>;

		template <typename... Args>
		inline constexpr bool is_adl_sol_lua_push_v = meta::is_detected_v<adl_sol_lua_push_test_t, Args...>;

		template <typename T, typename... Args>
		inline constexpr bool is_adl_sol_lua_push_exact_v = meta::is_detected_v<adl_sol_lua_push_exact_test_t, T, Args...>;
	}} // namespace meta::meta_detail


	namespace stack {
		namespace stack_detail {
			constexpr const char* not_enough_stack_space = "not enough space left on Lua stack";
			constexpr const char* not_enough_stack_space_floating = "not enough space left on Lua stack for a floating point number";
			constexpr const char* not_enough_stack_space_integral = "not enough space left on Lua stack for an integral number";
			constexpr const char* not_enough_stack_space_string = "not enough space left on Lua stack for a string";
			constexpr const char* not_enough_stack_space_meta_function_name = "not enough space left on Lua stack for the name of a meta_function";
			constexpr const char* not_enough_stack_space_userdata = "not enough space left on Lua stack to create a sol2 userdata";
			constexpr const char* not_enough_stack_space_generic = "not enough space left on Lua stack to push valuees";
			constexpr const char* not_enough_stack_space_environment = "not enough space left on Lua stack to retrieve environment";

			template <typename T>
			struct strip {
				typedef T type;
			};
			template <typename T>
			struct strip<std::reference_wrapper<T>> {
				typedef T& type;
			};
			template <typename T>
			struct strip<user<T>> {
				typedef T& type;
			};
			template <typename T>
			struct strip<non_null<T>> {
				typedef T type;
			};
			template <typename T>
			using strip_t = typename strip<T>::type;

			template <typename C>
			static int get_size_hint(C& c) {
				return static_cast<int>(c.size());
			}

			template <typename V, typename Al>
			static int get_size_hint(const std::forward_list<V, Al>&) {
				// forward_list makes me sad
				return static_cast<int>(32);
			}

			template <typename T>
			decltype(auto) unchecked_unqualified_get(lua_State* L, int index, record& tracking) {
				using Tu = meta::unqualified_t<T>;
				if constexpr (meta::meta_detail::is_adl_sol_lua_get_v<Tu>) {
					return sol_lua_get(types<Tu>(), L, index, tracking);
				}
				else {
					unqualified_getter<Tu> g {};
					(void)g;
					return g.get(L, index, tracking);
				}
			}

			template <typename T>
			decltype(auto) unchecked_get(lua_State* L, int index, record& tracking) {
				if constexpr (meta::meta_detail::is_adl_sol_lua_get_v<T>) {
					return sol_lua_get(types<T>(), L, index, tracking);
				}
				else {
					qualified_getter<T> g {};
					(void)g;
					return g.get(L, index, tracking);
				}
			}

			template <typename T>
			decltype(auto) unqualified_interop_get(lua_State* L, int index, void* unadjusted_pointer, record& tracking) {
				using Tu = meta::unqualified_t<T>;
				if constexpr (meta::meta_detail::is_adl_sol_lua_interop_get_v<Tu>) {
					return sol_lua_interop_get(types<Tu>(), L, index, unadjusted_pointer, tracking);
				}
				else {
					(void)L;
					(void)index;
					(void)unadjusted_pointer;
					(void)tracking;
					using Ti = stack_detail::strip_t<Tu>;
					return std::pair<bool, Ti*> { false, nullptr };
				}
			}

			template <typename T>
			decltype(auto) interop_get(lua_State* L, int index, void* unadjusted_pointer, record& tracking) {
				if constexpr (meta::meta_detail::is_adl_sol_lua_interop_get_v<T>) {
					return sol_lua_interop_get(types<T>(), L, index, unadjusted_pointer, tracking);
				}
				else {
					return unqualified_interop_get<T>(L, index, unadjusted_pointer, tracking);
				}
			}

			template <typename T, typename Handler>
			bool unqualified_interop_check(lua_State* L, int index, type index_type, Handler&& handler, record& tracking) {
				using Tu = meta::unqualified_t<T>;
				if constexpr (meta::meta_detail::is_adl_sol_lua_interop_check_v<Tu>) {
					return sol_lua_interop_check(types<Tu>(), L, index, index_type, std::forward<Handler>(handler), tracking);
				}
				else {
					(void)L;
					(void)index;
					(void)index_type;
					(void)handler;
					(void)tracking;
					return false;
				}
			}

			template <typename T, typename Handler>
			bool interop_check(lua_State* L, int index, type index_type, Handler&& handler, record& tracking) {
				if constexpr (meta::meta_detail::is_adl_sol_lua_interop_check_v<T>) {
					return sol_lua_interop_check(types<T>(), L, index, index_type, std::forward<Handler>(handler), tracking);
				}
				else {
					return unqualified_interop_check<T>(L, index, index_type, std::forward<Handler>(handler), tracking);
				}
			}

			using undefined_method_func = void (*)(stack_reference);

			struct undefined_metatable {
				lua_State* L;
				const char* key;
				undefined_method_func on_new_table;

				undefined_metatable(lua_State* l, const char* k, undefined_method_func umf) : L(l), key(k), on_new_table(umf) {
				}

				void operator()() const {
					if (luaL_newmetatable(L, key) == 1) {
						on_new_table(stack_reference(L, -1));
					}
					lua_setmetatable(L, -2);
				}
			};
		} // namespace stack_detail

		inline bool maybe_indexable(lua_State* L, int index = -1) {
			type t = type_of(L, index);
			return t == type::userdata || t == type::table;
		}

		inline int top(lua_State* L) {
			return lua_gettop(L);
		}

		inline bool is_main_thread(lua_State* L) {
			int ismainthread = lua_pushthread(L);
			lua_pop(L, 1);
			return ismainthread == 1;
		}

		inline void coroutine_create_guard(lua_State* L) {
			if (is_main_thread(L)) {
				return;
			}
			int stacksize = lua_gettop(L);
			if (stacksize < 1) {
				return;
			}
			if (type_of(L, 1) != type::function) {
				return;
			}
			// well now we're screwed...
			// we can clean the stack and pray it doesn't destroy anything?
			lua_pop(L, stacksize);
		}

		inline void clear(lua_State* L, int table_index) {
			lua_pushnil(L);
			while (lua_next(L, table_index) != 0) {
				// remove value
				lua_pop(L, 1);
				// duplicate key to protect form rawset
				lua_pushvalue(L, -1);
				// push new value
				lua_pushnil(L);
				// table_index%[key] = nil
				lua_rawset(L, table_index);
			}
		}

		inline void clear(reference& r) {
			auto pp = push_pop<false>(r);
			int stack_index = pp.index_of(r);
			clear(r.lua_state(), stack_index);
		}

		inline void clear(stack_reference& r) {
			clear(r.lua_state(), r.stack_index());
		}

		inline void clear(lua_State* L_, stateless_reference& r) {
			r.push(L_);
			int stack_index = absolute_index(L_, -1);
			clear(L_, stack_index);
			r.pop(L_);
		}

		inline void clear(lua_State* L_, stateless_stack_reference& r) {
			clear(L_, r.stack_index());
		}

		template <typename T, typename... Args>
		int push(lua_State* L, T&& t, Args&&... args) {
			using Tu = meta::unqualified_t<T>;
			if constexpr (meta::meta_detail::is_adl_sol_lua_push_exact_v<T, T, Args...>) {
				return sol_lua_push(types<T>(), L, std::forward<T>(t), std::forward<Args>(args)...);
			}
			else if constexpr (meta::meta_detail::is_adl_sol_lua_push_exact_v<Tu, T, Args...>) {
				return sol_lua_push(types<Tu>(), L, std::forward<T>(t), std::forward<Args>(args)...);
			}
			else if constexpr (meta::meta_detail::is_adl_sol_lua_push_v<T, Args...>) {
				return sol_lua_push(L, std::forward<T>(t), std::forward<Args>(args)...);
			}
			else {
				unqualified_pusher<Tu> p {};
				(void)p;
				return p.push(L, std::forward<T>(t), std::forward<Args>(args)...);
			}
		}

		// overload allows to use a pusher of a specific type, but pass in any kind of args
		template <typename T, typename Arg, typename... Args, typename = std::enable_if_t<!std::is_same<T, Arg>::value>>
		int push(lua_State* L, Arg&& arg, Args&&... args) {
			using Tu = meta::unqualified_t<T>;
			if constexpr (meta::meta_detail::is_adl_sol_lua_push_exact_v<T, Arg, Args...>) {
				return sol_lua_push(types<T>(), L, std::forward<Arg>(arg), std::forward<Args>(args)...);
			}
			else if constexpr (meta::meta_detail::is_adl_sol_lua_push_exact_v<Tu, Arg, Args...>) {
				return sol_lua_push(types<Tu>(), L, std::forward<Arg>(arg), std::forward<Args>(args)...);
			}
			else if constexpr (meta::meta_detail::is_adl_sol_lua_push_v<Arg, Args...> && !detail::is_tagged_v<Tu>) {
				return sol_lua_push(L, std::forward<Arg>(arg), std::forward<Args>(args)...);
			}
			else {
				unqualified_pusher<Tu> p {};
				(void)p;
				return p.push(L, std::forward<Arg>(arg), std::forward<Args>(args)...);
			}
		}

		template <typename T, typename... Args>
		int push_userdata(lua_State* L, T&& t, Args&&... args) {
			using U = meta::unqualified_t<T>;
			using Tr = meta::conditional_t<std::is_pointer_v<U>,
			     detail::as_pointer_tag<std::remove_pointer_t<U>>,
			     meta::conditional_t<is_unique_usertype_v<U>, detail::as_unique_tag<U>, detail::as_value_tag<U>>>;
			return stack::push<Tr>(L, std::forward<T>(t), std::forward<Args>(args)...);
		}

		template <typename T, typename Arg, typename... Args>
		int push_userdata(lua_State* L, Arg&& arg, Args&&... args) {
			using U = meta::unqualified_t<T>;
			using Tr = meta::conditional_t<std::is_pointer_v<U>,
			     detail::as_pointer_tag<std::remove_pointer_t<U>>,
			     meta::conditional_t<is_unique_usertype_v<U>, detail::as_unique_tag<U>, detail::as_value_tag<U>>>;
			return stack::push<Tr>(L, std::forward<Arg>(arg), std::forward<Args>(args)...);
		}

		namespace stack_detail {

			template <typename T, typename Arg, typename... Args>
			int push_reference(lua_State* L, Arg&& arg, Args&&... args) {
				// clang-format off
				using use_reference_tag =
				meta::all<
					meta::neg<is_value_semantic_for_function<T>>
#if SOL_IS_OFF(SOL_FUNCTION_CALL_VALUE_SEMANTICS)
					, std::is_lvalue_reference<T>,
					meta::neg<std::is_const<std::remove_reference_t<T>>>,
					meta::neg<is_lua_primitive<meta::unqualified_t<T>>>,
					meta::neg<is_unique_usertype<meta::unqualified_t<T>>>
#endif
				>;
				// clang-format on
				using Tr = meta::conditional_t<use_reference_tag::value, detail::as_reference_tag, meta::unqualified_t<T>>;
				return stack::push<Tr>(L, std::forward<Arg>(arg), std::forward<Args>(args)...);
			}

		} // namespace stack_detail

		template <typename T, typename... Args>
		int push_reference(lua_State* L, T&& t, Args&&... args) {
			return stack_detail::push_reference<T>(L, std::forward<T>(t), std::forward<Args>(args)...);
		}

		template <typename T, typename Arg, typename... Args>
		int push_reference(lua_State* L, Arg&& arg, Args&&... args) {
			return stack_detail::push_reference<T>(L, std::forward<Arg>(arg), std::forward<Args>(args)...);
		}

		inline int multi_push(lua_State*) {
			// do nothing
			return 0;
		}

		template <typename T, typename... Args>
		int multi_push(lua_State* L, T&& t, Args&&... args) {
			int pushcount = push(L, std::forward<T>(t));
			void(detail::swallow { (pushcount += stack::push(L, std::forward<Args>(args)), 0)... });
			return pushcount;
		}

		inline int multi_push_reference(lua_State*) {
			// do nothing
			return 0;
		}

		template <typename T, typename... Args>
		int multi_push_reference(lua_State* L, T&& t, Args&&... args) {
			int pushcount = stack::push_reference(L, std::forward<T>(t));
			void(detail::swallow { (pushcount += stack::push_reference(L, std::forward<Args>(args)), 0)... });
			return pushcount;
		}

		template <typename T, typename Handler>
		bool unqualified_check(lua_State* L, int index, Handler&& handler, record& tracking) {
			using Tu = meta::unqualified_t<T>;
			if constexpr (meta::meta_detail::is_adl_sol_lua_check_v<Tu>) {
				return sol_lua_check(types<Tu>(), L, index, std::forward<Handler>(handler), tracking);
			}
			else {
				unqualified_checker<Tu, lua_type_of_v<Tu>> c;
				// VC++ has a bad warning here: shut it up
				(void)c;
				return c.check(L, index, std::forward<Handler>(handler), tracking);
			}
		}

		template <typename T, typename Handler>
		bool unqualified_check(lua_State* L, int index, Handler&& handler) {
			record tracking {};
			return unqualified_check<T>(L, index, std::forward<Handler>(handler), tracking);
		}

		template <typename T>
		bool unqualified_check(lua_State* L, int index = -lua_size<meta::unqualified_t<T>>::value) {
			auto handler = &no_panic;
			return unqualified_check<T>(L, index, handler);
		}

		template <typename T, typename Handler>
		bool check(lua_State* L, int index, Handler&& handler, record& tracking) {
			if constexpr (meta::meta_detail::is_adl_sol_lua_check_v<T>) {
				return sol_lua_check(types<T>(), L, index, std::forward<Handler>(handler), tracking);
			}
			else {
				using Tu = meta::unqualified_t<T>;
				qualified_checker<T, lua_type_of_v<Tu>> c;
				// VC++ has a bad warning here: shut it up
				(void)c;
				return c.check(L, index, std::forward<Handler>(handler), tracking);
			}
		}

		template <typename T, typename Handler>
		bool check(lua_State* L, int index, Handler&& handler) {
			record tracking {};
			return check<T>(L, index, std::forward<Handler>(handler), tracking);
		}

		template <typename T>
		bool check(lua_State* L, int index = -lua_size<meta::unqualified_t<T>>::value) {
			auto handler = &no_panic;
			return check<T>(L, index, handler);
		}

		template <typename T, typename Handler>
		bool check_usertype(lua_State* L, int index, type, Handler&& handler, record& tracking) {
			using Tu = meta::unqualified_t<T>;
			using detail_t = meta::conditional_t<std::is_pointer_v<T>, detail::as_pointer_tag<Tu>, detail::as_value_tag<Tu>>;
			return check<detail_t>(L, index, std::forward<Handler>(handler), tracking);
		}

		template <typename T, typename Handler>
		bool check_usertype(lua_State* L, int index, Handler&& handler, record& tracking) {
			using Tu = meta::unqualified_t<T>;
			using detail_t = meta::conditional_t<std::is_pointer_v<T>, detail::as_pointer_tag<Tu>, detail::as_value_tag<Tu>>;
			return check<detail_t>(L, index, std::forward<Handler>(handler), tracking);
		}

		template <typename T, typename Handler>
		bool check_usertype(lua_State* L, int index, Handler&& handler) {
			record tracking {};
			return check_usertype<T>(L, index, std::forward<Handler>(handler), tracking);
		}

		template <typename T>
		bool check_usertype(lua_State* L, int index = -lua_size<meta::unqualified_t<T>>::value) {
			auto handler = &no_panic;
			return check_usertype<T>(L, index, handler);
		}

		template <typename T, typename Handler>
		decltype(auto) unqualified_check_get(lua_State* L, int index, Handler&& handler, record& tracking) {
			using Tu = meta::unqualified_t<T>;
			if constexpr (meta::meta_detail::is_adl_sol_lua_check_get_v<T>) {
				return sol_lua_check_get(types<T>(), L, index, std::forward<Handler>(handler), tracking);
			}
			else if constexpr (meta::meta_detail::is_adl_sol_lua_check_get_v<Tu>) {
				return sol_lua_check_get(types<Tu>(), L, index, std::forward<Handler>(handler), tracking);
			}
			else {
				unqualified_check_getter<Tu> cg {};
				(void)cg;
				return cg.get(L, index, std::forward<Handler>(handler), tracking);
			}
		}

		template <typename T, typename Handler>
		decltype(auto) unqualified_check_get(lua_State* L, int index, Handler&& handler) {
			record tracking {};
			return unqualified_check_get<T>(L, index, handler, tracking);
		}

		template <typename T>
		decltype(auto) unqualified_check_get(lua_State* L, int index = -lua_size<meta::unqualified_t<T>>::value) {
			auto handler = &no_panic;
			return unqualified_check_get<T>(L, index, handler);
		}

		template <typename T, typename Handler>
		decltype(auto) check_get(lua_State* L, int index, Handler&& handler, record& tracking) {
			if constexpr (meta::meta_detail::is_adl_sol_lua_check_get_v<T>) {
				return sol_lua_check_get(types<T>(), L, index, std::forward<Handler>(handler), tracking);
			}
			else {
				qualified_check_getter<T> cg {};
				(void)cg;
				return cg.get(L, index, std::forward<Handler>(handler), tracking);
			}
		}

		template <typename T, typename Handler>
		decltype(auto) check_get(lua_State* L, int index, Handler&& handler) {
			record tracking {};
			return check_get<T>(L, index, handler, tracking);
		}

		template <typename T>
		decltype(auto) check_get(lua_State* L, int index = -lua_size<meta::unqualified_t<T>>::value) {
			auto handler = &no_panic;
			return check_get<T>(L, index, handler);
		}

		namespace stack_detail {

			template <typename Handler>
			bool check_types(lua_State*, int, Handler&&, record&) {
				return true;
			}

			template <typename T, typename... Args, typename Handler>
			bool check_types(lua_State* L, int firstargument, Handler&& handler, record& tracking) {
				if (!stack::check<T>(L, firstargument + tracking.used, handler, tracking))
					return false;
				return check_types<Args...>(L, firstargument, std::forward<Handler>(handler), tracking);
			}

			template <typename... Args, typename Handler>
			bool check_types(types<Args...>, lua_State* L, int index, Handler&& handler, record& tracking) {
				return check_types<Args...>(L, index, std::forward<Handler>(handler), tracking);
			}

		} // namespace stack_detail

		template <typename... Args, typename Handler>
		bool multi_check(lua_State* L, int index, Handler&& handler, record& tracking) {
			return stack_detail::check_types<Args...>(L, index, std::forward<Handler>(handler), tracking);
		}

		template <typename... Args, typename Handler>
		bool multi_check(lua_State* L, int index, Handler&& handler) {
			record tracking {};
			return multi_check<Args...>(L, index, std::forward<Handler>(handler), tracking);
		}

		template <typename... Args>
		bool multi_check(lua_State* L, int index) {
			return multi_check<Args...>(L, index);
		}

		template <typename T>
		auto unqualified_get(lua_State* L, int index, record& tracking) -> decltype(stack_detail::unchecked_unqualified_get<T>(L, index, tracking)) {
#if SOL_IS_ON(SOL_SAFE_GETTER)
			static constexpr bool is_op = meta::is_optional_v<T>;
			if constexpr (is_op) {
				return stack_detail::unchecked_unqualified_get<T>(L, index, tracking);
			}
			else {
				if (is_lua_reference<T>::value) {
					return stack_detail::unchecked_unqualified_get<T>(L, index, tracking);
				}
				auto op = unqualified_check_get<T>(L, index, type_panic_c_str, tracking);
				return *std::move(op);
			}
#else
			return stack_detail::unchecked_unqualified_get<T>(L, index, tracking);
#endif
		}

		template <typename T>
		decltype(auto) unqualified_get(lua_State* L, int index = -lua_size<meta::unqualified_t<T>>::value) {
			record tracking {};
			return unqualified_get<T>(L, index, tracking);
		}

		template <typename T>
		auto get(lua_State* L, int index, record& tracking) -> decltype(stack_detail::unchecked_get<T>(L, index, tracking)) {
#if SOL_IS_ON(SOL_SAFE_GETTER)
			static constexpr bool is_op = meta::is_optional_v<T>;
			if constexpr (is_op) {
				return stack_detail::unchecked_get<T>(L, index, tracking);
			}
			else {
				if (is_lua_reference<T>::value) {
					return stack_detail::unchecked_get<T>(L, index, tracking);
				}
				auto op = check_get<T>(L, index, type_panic_c_str, tracking);
				return *std::move(op);
			}
#else
			return stack_detail::unchecked_get<T>(L, index, tracking);
#endif
		}

		template <typename T>
		decltype(auto) get(lua_State* L, int index = -lua_size<meta::unqualified_t<T>>::value) {
			record tracking {};
			return get<T>(L, index, tracking);
		}

		template <typename T>
		decltype(auto) get_usertype(lua_State* L, int index, record& tracking) {
			using UT = meta::conditional_t<std::is_pointer<T>::value, detail::as_pointer_tag<std::remove_pointer_t<T>>, detail::as_value_tag<T>>;
			return get<UT>(L, index, tracking);
		}

		template <typename T>
		decltype(auto) get_usertype(lua_State* L, int index = -lua_size_v<meta::unqualified_t<T>>) {
			record tracking {};
			return get_usertype<T>(L, index, tracking);
		}

		template <typename T>
		decltype(auto) pop(lua_State* L) {
			return popper<T> {}.pop(L);
		}

		template <bool global = false, bool raw = false, typename Key>
		void get_field(lua_State* L, Key&& key) {
			field_getter<meta::unqualified_t<Key>, global, raw> {}.get(L, std::forward<Key>(key));
		}

		template <bool global = false, bool raw = false, typename Key>
		void get_field(lua_State* L, Key&& key, int tableindex) {
			field_getter<meta::unqualified_t<Key>, global, raw> {}.get(L, std::forward<Key>(key), tableindex);
		}

		template <bool global = false, typename Key>
		void raw_get_field(lua_State* L, Key&& key) {
			get_field<global, true>(L, std::forward<Key>(key));
		}

		template <bool global = false, typename Key>
		void raw_get_field(lua_State* L, Key&& key, int tableindex) {
			get_field<global, true>(L, std::forward<Key>(key), tableindex);
		}

		template <bool global = false, bool raw = false, typename C = detail::non_lua_nil_t, typename Key>
		probe probe_get_field(lua_State* L, Key&& key) {
			return probe_field_getter<meta::unqualified_t<Key>, C, global, raw> {}.get(L, std::forward<Key>(key));
		}

		template <bool global = false, bool raw = false, typename C = detail::non_lua_nil_t, typename Key>
		probe probe_get_field(lua_State* L, Key&& key, int tableindex) {
			return probe_field_getter<meta::unqualified_t<Key>, C, global, raw> {}.get(L, std::forward<Key>(key), tableindex);
		}

		template <bool global = false, typename C = detail::non_lua_nil_t, typename Key>
		probe probe_raw_get_field(lua_State* L, Key&& key) {
			return probe_get_field<global, true, C>(L, std::forward<Key>(key));
		}

		template <bool global = false, typename C = detail::non_lua_nil_t, typename Key>
		probe probe_raw_get_field(lua_State* L, Key&& key, int tableindex) {
			return probe_get_field<global, true, C>(L, std::forward<Key>(key), tableindex);
		}

		template <bool global = false, bool raw = false, typename Key, typename Value>
		void set_field(lua_State* L, Key&& key, Value&& value) {
			field_setter<meta::unqualified_t<Key>, global, raw> {}.set(L, std::forward<Key>(key), std::forward<Value>(value));
		}

		template <bool global = false, bool raw = false, typename Key, typename Value>
		void set_field(lua_State* L, Key&& key, Value&& value, int tableindex) {
			field_setter<meta::unqualified_t<Key>, global, raw> {}.set(L, std::forward<Key>(key), std::forward<Value>(value), tableindex);
		}

		template <bool global = false, typename Key, typename Value>
		void raw_set_field(lua_State* L, Key&& key, Value&& value) {
			set_field<global, true>(L, std::forward<Key>(key), std::forward<Value>(value));
		}

		template <bool global = false, typename Key, typename Value>
		void raw_set_field(lua_State* L, Key&& key, Value&& value, int tableindex) {
			set_field<global, true>(L, std::forward<Key>(key), std::forward<Value>(value), tableindex);
		}

		template <typename T, typename F>
		void modify_unique_usertype_as(const stack_reference& obj, F&& f) {
			void* raw = lua_touserdata(obj.lua_state(), obj.stack_index());
			void* ptr_memory = detail::align_usertype_pointer(raw);
			void* uu_memory = detail::align_usertype_unique<T>(raw);
			T& uu = *static_cast<T*>(uu_memory);
			f(uu);
			*static_cast<void**>(ptr_memory) = static_cast<void*>(detail::unique_get(obj.lua_state(), uu));
		}

		template <typename F>
		void modify_unique_usertype(const stack_reference& obj, F&& f) {
			using bt = meta::bind_traits<meta::unqualified_t<F>>;
			using T = typename bt::template arg_at<0>;
			using Tu = meta::unqualified_t<T>;
			modify_unique_usertype_as<Tu>(obj, std::forward<F>(f));
		}

		namespace stack_detail {
			template <typename T, typename Handler>
			decltype(auto) check_get_arg(lua_State* L_, int index_, Handler&& handler_, record& tracking_) {
				if constexpr (meta::meta_detail::is_adl_sol_lua_check_access_v<T>) {
					sol_lua_check_access(types<meta::unqualified_t<T>>(), L_, index_, tracking_);
				}
				return check_get<T>(L_, index_, std::forward<Handler>(handler_), tracking_);
			}

			template <typename T>
			decltype(auto) unchecked_get_arg(lua_State* L_, int index_, record& tracking_) {
				if constexpr (meta::meta_detail::is_adl_sol_lua_check_access_v<T>) {
					sol_lua_check_access(types<meta::unqualified_t<T>>(), L_, index_, tracking_);
				}
				return unchecked_get<T>(L_, index_, tracking_);
			}
		} // namespace stack_detail

	} // namespace stack

	namespace detail {

		template <typename T>
		lua_CFunction make_destructor(std::true_type) {
			if constexpr (is_unique_usertype_v<T>) {
				return &unique_destroy<T>;
			}
			else if constexpr (!std::is_pointer_v<T>) {
				return &usertype_alloc_destroy<T>;
			}
			else {
				return &cannot_destroy<T>;
			}
		}

		template <typename T>
		lua_CFunction make_destructor(std::false_type) {
			return &cannot_destroy<T>;
		}

		template <typename T>
		lua_CFunction make_destructor() {
			return make_destructor<T>(std::is_destructible<T>());
		}

		struct no_comp {
			template <typename A, typename B>
			bool operator()(A&&, B&&) const {
				return false;
			}
		};

		template <typename T>
		int is_check(lua_State* L) {
			return stack::push(L, stack::check<T>(L, 1, &no_panic));
		}

		template <typename T>
		int member_default_to_string(std::true_type, lua_State* L) {
			decltype(auto) ts = stack::get<T>(L, 1).to_string();
			return stack::push(L, std::forward<decltype(ts)>(ts));
		}

		template <typename T>
		int member_default_to_string(std::false_type, lua_State* L) {
			return luaL_error(L,
			     "cannot perform to_string on '%s': no 'to_string' overload in namespace, 'to_string' member "
			     "function, or operator<<(ostream&, ...) present",
			     detail::demangle<T>().data());
		}

		template <typename T>
		int adl_default_to_string(std::true_type, lua_State* L) {
			using namespace std;
			decltype(auto) ts = to_string(stack::get<T>(L, 1));
			return stack::push(L, std::forward<decltype(ts)>(ts));
		}

		template <typename T>
		int adl_default_to_string(std::false_type, lua_State* L) {
			return member_default_to_string<T>(meta::supports_to_string_member<T>(), L);
		}

		template <typename T>
		int oss_default_to_string(std::true_type, lua_State* L) {
			std::ostringstream oss;
			oss << stack::unqualified_get<T>(L, 1);
			return stack::push(L, oss.str());
		}

		template <typename T>
		int oss_default_to_string(std::false_type, lua_State* L) {
			return adl_default_to_string<T>(meta::supports_adl_to_string<T>(), L);
		}

		template <typename T>
		int default_to_string(lua_State* L) {
			return oss_default_to_string<T>(meta::supports_op_left_shift<std::ostream, T>(), L);
		}

		template <typename T>
		int default_size(lua_State* L) {
			decltype(auto) self = stack::unqualified_get<T>(L, 1);
			return stack::push(L, self.size());
		}

		template <typename T, typename Op>
		int comparsion_operator_wrap(lua_State* L) {
			if constexpr (std::is_void_v<T>) {
				return stack::push(L, false);
			}
			else {
				auto maybel = stack::unqualified_check_get<T>(L, 1);
				if (!maybel) {
					return stack::push(L, false);
				}
				auto mayber = stack::unqualified_check_get<T>(L, 2);
				if (!mayber) {
					return stack::push(L, false);
				}
				decltype(auto) l = *maybel;
				decltype(auto) r = *mayber;
				if constexpr (std::is_same_v<no_comp, Op>) {
					std::equal_to<> op;
					return stack::push(L, op(detail::ptr(l), detail::ptr(r)));
				}
				else {
					if constexpr (std::is_same_v<std::equal_to<>, Op> // clang-format hack
					     || std::is_same_v<std::less_equal<>, Op>     //
					     || std::is_same_v<std::less_equal<>, Op>) {  //
						if (detail::ptr(l) == detail::ptr(r)) {
							return stack::push(L, true);
						}
					}
					Op op;
					return stack::push(L, op(detail::deref(l), detail::deref(r)));
				}
			}
		}

		template <typename T, typename IFx, typename Fx>
		void insert_default_registrations(IFx&& ifx, Fx&& fx);

		template <typename T, bool, bool>
		struct get_is_primitive : is_lua_primitive<T> { };

		template <typename T>
		struct get_is_primitive<T, true, false>
		: meta::neg<std::is_reference<decltype(sol_lua_get(types<T>(), nullptr, -1, std::declval<stack::record&>()))>> { };

		template <typename T>
		struct get_is_primitive<T, false, true>
		: meta::neg<std::is_reference<decltype(sol_lua_get(types<meta::unqualified_t<T>>(), nullptr, -1, std::declval<stack::record&>()))>> { };

		template <typename T>
		struct get_is_primitive<T, true, true> : get_is_primitive<T, true, false> { };

	} // namespace detail

	template <typename T>
	struct is_proxy_primitive
	: detail::get_is_primitive<T, meta::meta_detail::is_adl_sol_lua_get_v<T>, meta::meta_detail::is_adl_sol_lua_get_v<meta::unqualified_t<T>>> { };

} // namespace sol

#endif // SOL_STACK_CORE_HPP