diff --git a/.gitmodules b/.gitmodules
index f6ae162a..570fde0f 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,6 +1,3 @@
 [submodule "Catch"]
 	path = Catch
-	url = https://github.com/philsquared/Catch.git
-[submodule "Optional"]
-	path = Optional
-	url = https://github.com/ThePhD/Optional.git
+	url = https://github.com/philsquared/Catch.git
\ No newline at end of file
diff --git a/sol/object.hpp b/sol/object.hpp
index 5a038a3a..fafa0b68 100644
--- a/sol/object.hpp
+++ b/sol/object.hpp
@@ -22,11 +22,11 @@
 #ifndef SOL_OBJECT_HPP
 #define SOL_OBJECT_HPP
 
-#include "optional.hpp"
 #include "reference.hpp"
 #include "stack.hpp"
 #include "userdata.hpp"
 #include "variadic_args.hpp"
+#include "optional.hpp"
 
 namespace sol {
 
diff --git a/sol/optional.hpp b/sol/optional.hpp
index 823bdc3d..16f805e4 100644
--- a/sol/optional.hpp
+++ b/sol/optional.hpp
@@ -22,11 +22,12 @@
 #ifndef SOL_OPTIONAL_HPP
 #define SOL_OPTIONAL_HPP
 
+#include "compatibility.hpp"
 #include "in_place.hpp"
 #if defined(SOL_USE_BOOST)
 #include <boost/optional.hpp>
 #else
-#include "../Optional/optional.hpp"
+#include "optional_implementation.hpp"
 #endif // Boost vs. Better optional
 
 namespace sol {
diff --git a/sol/optional_implementation.hpp b/sol/optional_implementation.hpp
new file mode 100644
index 00000000..b4d58a32
--- /dev/null
+++ b/sol/optional_implementation.hpp
@@ -0,0 +1,1141 @@
+// The MIT License (MIT) 
+
+// Copyright (c) 2013-2016 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.
+
+// Copyright (C) 2011 - 2012 Andrzej Krzemienski.
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// The idea and interface is based on Boost.Optional library
+// authored by Fernando Luis Cacciola Carballal
+
+# ifndef ___SOL_OPTIONAL_HPP___
+# define ___SOL_OPTIONAL_HPP___
+
+# include <utility>
+# include <type_traits>
+# include <initializer_list>
+# include <cassert>
+# include <functional>
+# include <string>
+# include <stdexcept>
+#ifdef SOL_NO_EXCEPTIONS
+#include <cstdlib>
+#endif // Exceptions
+
+# define TR2_OPTIONAL_REQUIRES(...) typename ::std::enable_if<__VA_ARGS__::value, bool>::type = false
+
+# if defined __GNUC__ // NOTE: GNUC is also defined for Clang
+#   if (__GNUC__ >= 5)
+#     define TR2_OPTIONAL_GCC_5_0_AND_HIGHER___
+#     define TR2_OPTIONAL_GCC_4_8_AND_HIGHER___
+#   elif (__GNUC__ == 4) && (__GNUC_MINOR__ >= 8)
+#     define TR2_OPTIONAL_GCC_4_8_AND_HIGHER___
+#   elif (__GNUC__ > 4)
+#     define TR2_OPTIONAL_GCC_4_8_AND_HIGHER___
+#   endif
+#
+#   if (__GNUC__ == 4) && (__GNUC_MINOR__ >= 7)
+#     define TR2_OPTIONAL_GCC_4_7_AND_HIGHER___
+#   elif (__GNUC__ > 4)
+#     define TR2_OPTIONAL_GCC_4_7_AND_HIGHER___
+#   endif
+#
+#   if (__GNUC__ == 4) && (__GNUC_MINOR__ == 8) && (__GNUC_PATCHLEVEL__ >= 1)
+#     define TR2_OPTIONAL_GCC_4_8_1_AND_HIGHER___
+#   elif (__GNUC__ == 4) && (__GNUC_MINOR__ >= 9)
+#     define TR2_OPTIONAL_GCC_4_8_1_AND_HIGHER___
+#   elif (__GNUC__ > 4)
+#     define TR2_OPTIONAL_GCC_4_8_1_AND_HIGHER___
+#   endif
+# endif
+#
+# if defined __clang_major__
+#   if (__clang_major__ == 3 && __clang_minor__ >= 5)
+#     define TR2_OPTIONAL_CLANG_3_5_AND_HIGHTER_
+#   elif (__clang_major__ > 3)
+#     define TR2_OPTIONAL_CLANG_3_5_AND_HIGHTER_
+#   endif
+#   if defined TR2_OPTIONAL_CLANG_3_5_AND_HIGHTER_
+#     define TR2_OPTIONAL_CLANG_3_4_2_AND_HIGHER_
+#   elif (__clang_major__ == 3 && __clang_minor__ == 4 && __clang_patchlevel__ >= 2)
+#     define TR2_OPTIONAL_CLANG_3_4_2_AND_HIGHER_
+#   endif
+# endif
+#
+# if defined _MSC_VER
+#   if (_MSC_VER >= 1900)
+#     define TR2_OPTIONAL_MSVC_2015_AND_HIGHER___
+#   endif
+# endif
+
+# if defined __clang__
+#   if (__clang_major__ > 2) || (__clang_major__ == 2) && (__clang_minor__ >= 9)
+#     define OPTIONAL_HAS_THIS_RVALUE_REFS 1
+#   else
+#     define OPTIONAL_HAS_THIS_RVALUE_REFS 0
+#   endif
+# elif defined TR2_OPTIONAL_GCC_4_8_1_AND_HIGHER___
+#   define OPTIONAL_HAS_THIS_RVALUE_REFS 1
+# elif defined TR2_OPTIONAL_MSVC_2015_AND_HIGHER___
+#   define OPTIONAL_HAS_THIS_RVALUE_REFS 1
+# else
+#   define OPTIONAL_HAS_THIS_RVALUE_REFS 0
+# endif
+
+
+# if defined TR2_OPTIONAL_GCC_4_8_1_AND_HIGHER___
+#   define OPTIONAL_HAS_CONSTEXPR_INIT_LIST 1
+#   define OPTIONAL_CONSTEXPR_INIT_LIST constexpr
+# else
+#   define OPTIONAL_HAS_CONSTEXPR_INIT_LIST 0
+#   define OPTIONAL_CONSTEXPR_INIT_LIST
+# endif
+
+# if defined TR2_OPTIONAL_CLANG_3_5_AND_HIGHTER_ && (defined __cplusplus) && (__cplusplus != 201103L)
+#   define OPTIONAL_HAS_MOVE_ACCESSORS 1
+# else
+#   define OPTIONAL_HAS_MOVE_ACCESSORS 0
+# endif
+
+# // In C++11 constexpr implies const, so we need to make non-const members also non-constexpr
+# if (defined __cplusplus) && (__cplusplus == 201103L)
+#   define OPTIONAL_MUTABLE_CONSTEXPR
+# else
+#   define OPTIONAL_MUTABLE_CONSTEXPR constexpr
+# endif
+
+namespace sol {
+
+	// BEGIN workaround for missing is_trivially_destructible
+# if defined TR2_OPTIONAL_GCC_4_8_AND_HIGHER___
+	// leave it: it is already there
+# elif defined TR2_OPTIONAL_CLANG_3_4_2_AND_HIGHER_
+	// leave it: it is already there
+# elif defined TR2_OPTIONAL_MSVC_2015_AND_HIGHER___
+	// leave it: it is already there
+# elif defined TR2_OPTIONAL_DISABLE_EMULATION_OF_TYPE_TRAITS
+	// leave it: the user doesn't want it
+# else
+	template <typename T>
+	using is_trivially_destructible = ::std::has_trivial_destructor<T>;
+# endif
+	// END workaround for missing is_trivially_destructible
+
+# if (defined TR2_OPTIONAL_GCC_4_7_AND_HIGHER___)
+	// leave it; our metafunctions are already defined.
+# elif defined TR2_OPTIONAL_CLANG_3_4_2_AND_HIGHER_
+	// leave it; our metafunctions are already defined.
+# elif defined TR2_OPTIONAL_MSVC_2015_AND_HIGHER___
+	// leave it: it is already there
+# elif defined TR2_OPTIONAL_DISABLE_EMULATION_OF_TYPE_TRAITS
+	// leave it: the user doesn't want it
+# else
+
+
+// workaround for missing traits in GCC and CLANG
+	template <class T>
+	struct is_nothrow_move_constructible
+	{
+		constexpr static bool value = ::std::is_nothrow_constructible<T, T&&>::value;
+	};
+
+
+	template <class T, class U>
+	struct is_assignable
+	{
+		template <class X, class Y>
+		constexpr static bool has_assign(...) { return false; }
+
+		template <class X, class Y, size_t S = sizeof((::std::declval<X>() = ::std::declval<Y>(), true)) >
+		// the comma operator is necessary for the cases where operator= returns void
+		constexpr static bool has_assign(bool) { return true; }
+
+		constexpr static bool value = has_assign<T, U>(true);
+	};
+
+
+	template <class T>
+	struct is_nothrow_move_assignable
+	{
+		template <class X, bool has_any_move_assign>
+		struct has_nothrow_move_assign {
+			constexpr static bool value = false;
+		};
+
+		template <class X>
+		struct has_nothrow_move_assign<X, true> {
+			constexpr static bool value = noexcept(::std::declval<X&>() = ::std::declval<X&&>());
+		};
+
+		constexpr static bool value = has_nothrow_move_assign<T, is_assignable<T&, T&&>::value>::value;
+	};
+	// end workaround
+
+
+# endif
+
+
+
+// 20.5.4, optional for object types
+	template <class T> class optional;
+
+	// 20.5.5, optional for lvalue reference types
+	template <class T> class optional<T&>;
+
+
+	// workaround: std utility functions aren't constexpr yet
+	template <class T> inline constexpr T&& constexpr_forward(typename ::std::remove_reference<T>::type& t) noexcept
+	{
+		return static_cast<T&&>(t);
+	}
+
+	template <class T> inline constexpr T&& constexpr_forward(typename ::std::remove_reference<T>::type&& t) noexcept
+	{
+		static_assert(!::std::is_lvalue_reference<T>::value, "!!");
+		return static_cast<T&&>(t);
+	}
+
+	template <class T> inline constexpr typename ::std::remove_reference<T>::type&& constexpr_move(T&& t) noexcept
+	{
+		return static_cast<typename ::std::remove_reference<T>::type&&>(t);
+	}
+
+
+#if defined NDEBUG
+# define TR2_OPTIONAL_ASSERTED_EXPRESSION(CHECK, EXPR) (EXPR)
+#else
+# define TR2_OPTIONAL_ASSERTED_EXPRESSION(CHECK, EXPR) ((CHECK) ? (EXPR) : ([]{assert(!#CHECK);}(), (EXPR)))
+#endif
+
+
+	namespace detail_
+	{
+
+		// static_addressof: a constexpr version of addressof
+		template <typename T>
+		struct has_overloaded_addressof
+		{
+			template <class X>
+			constexpr static bool has_overload(...) { return false; }
+
+			template <class X, size_t S = sizeof(::std::declval<X&>().operator&()) >
+			constexpr static bool has_overload(bool) { return true; }
+
+			constexpr static bool value = has_overload<T>(true);
+		};
+
+		template <typename T, TR2_OPTIONAL_REQUIRES(!has_overloaded_addressof<T>)>
+		constexpr T* static_addressof(T& ref)
+		{
+			return &ref;
+		}
+
+		template <typename T, TR2_OPTIONAL_REQUIRES(has_overloaded_addressof<T>)>
+		T* static_addressof(T& ref)
+		{
+			return ::std::addressof(ref);
+		}
+
+
+		// the call to convert<A>(b) has return type A and converts b to type A iff b decltype(b) is implicitly convertible to A  
+		template <class U>
+		constexpr U convert(U v) { return v; }
+
+	} // namespace detail_
+
+	constexpr struct trivial_init_t {} trivial_init{};
+
+	// 20.5.7, Disengaged state indicator
+	struct nullopt_t
+	{
+		struct init {};
+		constexpr explicit nullopt_t(init) {}
+	};
+	constexpr nullopt_t nullopt{ nullopt_t::init() };
+
+
+	// 20.5.8, class bad_optional_access
+	class bad_optional_access : public ::std::logic_error {
+	public:
+		explicit bad_optional_access(const ::std::string& what_arg) : ::std::logic_error{ what_arg } {}
+		explicit bad_optional_access(const char* what_arg) : ::std::logic_error{ what_arg } {}
+	};
+
+
+	template <class T>
+	struct optional_base
+	{
+		bool init_;
+		char storage_[sizeof(T)];
+
+		constexpr optional_base() noexcept : init_(false), storage_() {};
+
+		explicit optional_base(const T& v) : init_(true), storage_() {
+			new (&storage())T(v);
+		}
+
+		explicit optional_base(T&& v) : init_(true), storage_() {
+			new (&storage())T(constexpr_move(v));
+		}
+
+		template <class... Args> explicit optional_base(in_place_t, Args&&... args)
+			: init_(true), storage_() {
+			new (&storage())T(constexpr_forward<Args>(args)...);
+		}
+
+		template <class U, class... Args, TR2_OPTIONAL_REQUIRES(::std::is_constructible<T, ::std::initializer_list<U>>)>
+		explicit optional_base(in_place_t, ::std::initializer_list<U> il, Args&&... args)
+			: init_(true), storage_() {
+			new (&storage())T(il, constexpr_forward<Args>(args)...);
+		}
+#if defined __GNUC__ 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstrict-aliasing"
+#endif
+		T& storage() {
+			return *reinterpret_cast<T*>(&storage_[0]);
+		}
+
+		constexpr const T& storage() const {
+			return *reinterpret_cast<T const*>(&storage_[0]);
+		}
+#if defined __GNUC__
+#pragma GCC diagnostic pop
+#endif
+
+		~optional_base() { if (init_) { storage().T::~T(); } }
+	};
+
+#if defined __GNUC__ && !defined TR2_OPTIONAL_GCC_5_0_AND_HIGHER___
+	// Sorry, GCC 4.x; you're just a piece of shit
+	template <typename T>
+	using constexpr_optional_base = optional_base<T>;
+#else
+	template <class T>
+	struct constexpr_optional_base
+	{
+		bool init_;
+		char storage_[sizeof(T)];
+		constexpr constexpr_optional_base() noexcept : init_(false), storage_() {}
+
+		explicit constexpr constexpr_optional_base(const T& v) : init_(true), storage_() {
+			new (&storage())T(v);
+		}
+
+		explicit constexpr constexpr_optional_base(T&& v) : init_(true), storage_() {
+			new (&storage())T(constexpr_move(v));
+		}
+
+		template <class... Args> explicit constexpr constexpr_optional_base(in_place_t, Args&&... args)
+			: init_(true), storage_() {
+			new (&storage())T(constexpr_forward<Args>(args)...);
+		}
+
+		template <class U, class... Args, TR2_OPTIONAL_REQUIRES(::std::is_constructible<T, ::std::initializer_list<U>>)>
+		OPTIONAL_CONSTEXPR_INIT_LIST explicit constexpr_optional_base(in_place_t, ::std::initializer_list<U> il, Args&&... args)
+			: init_(true), storage_() {
+			new (&storage())T(il, constexpr_forward<Args>(args)...);
+		}
+
+#if defined __GNUC__ 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstrict-aliasing"
+#endif
+		T& storage() {
+			return (*reinterpret_cast<T*>(&storage_[0]));
+		}
+
+		constexpr const T& storage() const {
+			return (*reinterpret_cast<T const*>(&storage_[0]));
+		}
+#if defined __GNUC__
+#pragma GCC diagnostic pop
+#endif
+
+		~constexpr_optional_base() = default;
+	};
+#endif
+
+	template <class T>
+	using OptionalBase = typename ::std::conditional<
+		::std::is_trivially_destructible<T>::value,
+		constexpr_optional_base<typename ::std::remove_const<T>::type>,
+		optional_base<typename ::std::remove_const<T>::type>
+	>::type;
+
+
+
+	template <class T>
+	class optional : private OptionalBase<T>
+	{
+		static_assert(!::std::is_same<typename ::std::decay<T>::type, nullopt_t>::value, "bad T");
+		static_assert(!::std::is_same<typename ::std::decay<T>::type, in_place_t>::value, "bad T");
+
+
+		constexpr bool initialized() const noexcept { return OptionalBase<T>::init_; }
+		typename ::std::remove_const<T>::type* dataptr() { return ::std::addressof(OptionalBase<T>::storage()); }
+		constexpr const T* dataptr() const { return detail_::static_addressof(OptionalBase<T>::storage()); }
+
+# if OPTIONAL_HAS_THIS_RVALUE_REFS == 1
+		constexpr const T& contained_val() const& { return OptionalBase<T>::storage(); }
+#   if OPTIONAL_HAS_MOVE_ACCESSORS == 1
+		OPTIONAL_MUTABLE_CONSTEXPR T&& contained_val() && { return ::std::move(OptionalBase<T>::storage()); }
+		OPTIONAL_MUTABLE_CONSTEXPR T& contained_val() & { return OptionalBase<T>::storage(); }
+#   else
+		T& contained_val() & { return OptionalBase<T>::storage(); }
+		T&& contained_val() && { return ::std::move(OptionalBase<T>::storage()); }
+#   endif
+# else
+		constexpr const T& contained_val() const { return OptionalBase<T>::storage(); }
+		T& contained_val() { return OptionalBase<T>::storage(); }
+# endif
+
+		void clear() noexcept {
+			if (initialized()) dataptr()->T::~T();
+			OptionalBase<T>::init_ = false;
+		}
+
+		template <class... Args>
+		void initialize(Args&&... args) noexcept(noexcept(T(::std::forward<Args>(args)...)))
+		{
+			assert(!OptionalBase<T>::init_);
+			::new (static_cast<void*>(dataptr())) T(::std::forward<Args>(args)...);
+			OptionalBase<T>::init_ = true;
+		}
+
+		template <class U, class... Args>
+		void initialize(::std::initializer_list<U> il, Args&&... args) noexcept(noexcept(T(il, ::std::forward<Args>(args)...)))
+		{
+			assert(!OptionalBase<T>::init_);
+			::new (static_cast<void*>(dataptr())) T(il, ::std::forward<Args>(args)...);
+			OptionalBase<T>::init_ = true;
+		}
+
+	public:
+		typedef T value_type;
+
+		// 20.5.5.1, constructors
+		constexpr optional() noexcept : OptionalBase<T>() {};
+		constexpr optional(nullopt_t) noexcept : OptionalBase<T>() {};
+
+		optional(const optional& rhs)
+			: OptionalBase<T>()
+		{
+			if (rhs.initialized()) {
+				::new (static_cast<void*>(dataptr())) T(*rhs);
+				OptionalBase<T>::init_ = true;
+			}
+		}
+
+		optional(const optional<T&>& rhs) : optional()
+		{
+			if (rhs) {
+				::new (static_cast<void*>(dataptr())) T(*rhs);
+				OptionalBase<T>::init_ = true;
+			}
+		}
+
+
+		optional(optional&& rhs) noexcept(::std::is_nothrow_move_constructible<T>::value)
+			: OptionalBase<T>()
+		{
+			if (rhs.initialized()) {
+				::new (static_cast<void*>(dataptr())) T(::std::move(*rhs));
+				OptionalBase<T>::init_ = true;
+			}
+		}
+
+		constexpr optional(const T& v) : OptionalBase<T>(v) {}
+
+		constexpr optional(T&& v) : OptionalBase<T>(constexpr_move(v)) {}
+
+		template <class... Args>
+		explicit constexpr optional(in_place_t, Args&&... args)
+			: OptionalBase<T>(in_place, constexpr_forward<Args>(args)...) {}
+
+		template <class U, class... Args, TR2_OPTIONAL_REQUIRES(::std::is_constructible<T, ::std::initializer_list<U>>)>
+		OPTIONAL_CONSTEXPR_INIT_LIST explicit optional(in_place_t, ::std::initializer_list<U> il, Args&&... args)
+			: OptionalBase<T>(in_place, il, constexpr_forward<Args>(args)...) {}
+
+		// 20.5.4.2, Destructor
+		~optional() = default;
+
+		// 20.5.4.3, assignment
+		optional& operator=(nullopt_t) noexcept
+		{
+			clear();
+			return *this;
+		}
+
+		optional& operator=(const optional& rhs)
+		{
+			if (initialized() == true && rhs.initialized() == false) clear();
+			else if (initialized() == false && rhs.initialized() == true)  initialize(*rhs);
+			else if (initialized() == true && rhs.initialized() == true)  contained_val() = *rhs;
+			return *this;
+		}
+
+		optional& operator=(optional&& rhs)
+			noexcept(::std::is_nothrow_move_assignable<T>::value && ::std::is_nothrow_move_constructible<T>::value)
+		{
+			if (initialized() == true && rhs.initialized() == false) clear();
+			else if (initialized() == false && rhs.initialized() == true)  initialize(::std::move(*rhs));
+			else if (initialized() == true && rhs.initialized() == true)  contained_val() = ::std::move(*rhs);
+			return *this;
+		}
+
+		template <class U>
+		auto operator=(U&& v)
+			-> typename ::std::enable_if
+			<
+			::std::is_same<typename ::std::decay<U>::type, T>::value,
+			optional&
+			>::type
+		{
+			if (initialized()) { contained_val() = ::std::forward<U>(v); }
+			else { initialize(::std::forward<U>(v)); }
+			return *this;
+		}
+
+
+		template <class... Args>
+		void emplace(Args&&... args)
+		{
+			clear();
+			initialize(::std::forward<Args>(args)...);
+		}
+
+		template <class U, class... Args>
+		void emplace(::std::initializer_list<U> il, Args&&... args)
+		{
+			clear();
+			initialize<U, Args...>(il, ::std::forward<Args>(args)...);
+		}
+
+		// 20.5.4.4, Swap
+		void swap(optional<T>& rhs) noexcept(::std::is_nothrow_move_constructible<T>::value && noexcept(swap(::std::declval<T&>(), ::std::declval<T&>())))
+		{
+			if (initialized() == true && rhs.initialized() == false) { rhs.initialize(::std::move(**this)); clear(); }
+			else if (initialized() == false && rhs.initialized() == true) { initialize(::std::move(*rhs)); rhs.clear(); }
+			else if (initialized() == true && rhs.initialized() == true) { using ::std::swap; swap(**this, *rhs); }
+		}
+
+		// 20.5.4.5, Observers
+
+		explicit constexpr operator bool() const noexcept { return initialized(); }
+
+		constexpr T const* operator ->() const {
+			return TR2_OPTIONAL_ASSERTED_EXPRESSION(initialized(), dataptr());
+		}
+
+# if OPTIONAL_HAS_MOVE_ACCESSORS == 1
+
+		OPTIONAL_MUTABLE_CONSTEXPR T* operator ->() {
+			assert(initialized());
+			return dataptr();
+		}
+
+		constexpr T const& operator *() const& {
+			return TR2_OPTIONAL_ASSERTED_EXPRESSION(initialized(), contained_val());
+		}
+
+		OPTIONAL_MUTABLE_CONSTEXPR T& operator *() & {
+			assert(initialized());
+			return contained_val();
+		}
+
+		OPTIONAL_MUTABLE_CONSTEXPR T&& operator *() && {
+			assert(initialized());
+			return constexpr_move(contained_val());
+		}
+
+		constexpr T const& value() const& {
+			if (initialized()) {
+				return contained_val();
+			}
+#ifdef SOL_NO_EXCEPTIONS
+			// No abort in constexpr
+			//std::abort();
+			T* noreach = (T*)nullptr;
+			return *noreach;
+#else
+			throw bad_optional_access("bad optional access")
+#endif
+		}
+
+		OPTIONAL_MUTABLE_CONSTEXPR T& value() & {
+			if (initialized()) {
+				return contained_val();
+			}
+#ifdef SOL_NO_EXCEPTIONS
+			// No abort in constexpr
+			//std::abort();
+			T* noreach = (T*)nullptr;
+			return *noreach;
+#else
+			throw bad_optional_access("bad optional access")
+#endif
+		}
+
+		OPTIONAL_MUTABLE_CONSTEXPR T&& value() && {
+			if (initialized()) {
+				return std::move(contained_val());
+			}
+#ifdef SOL_NO_EXCEPTIONS
+			// No abort in constexpr
+			//std::abort();
+			T* noreach = (T*)nullptr;
+			return std::move(*noreach);
+#else
+			throw bad_optional_access("bad optional access")
+#endif
+
+		}
+
+# else
+
+		T* operator ->() {
+			assert(initialized());
+			return dataptr();
+		}
+
+		constexpr T const& operator *() const {
+			return TR2_OPTIONAL_ASSERTED_EXPRESSION(initialized(), contained_val());
+		}
+
+		T& operator *() {
+			assert(initialized());
+			return contained_val();
+		}
+
+		constexpr T const& value() const {
+			if (initialized()) {
+				return contained_val();
+			}
+#ifdef SOL_NO_EXCEPTIONS
+			// No abort in constexpr
+			//std::abort();
+			T* noreach = (T*)nullptr;
+			return *noreach;
+#else
+			throw bad_optional_access("bad optional access")
+#endif
+		}
+
+		T& value() {
+			if (initialized()) {
+				return contained_val();
+			}
+#ifdef SOL_NO_EXCEPTIONS
+			std::abort();
+			T* noreach = (T*)nullptr;
+			return *noreach;
+#else
+			throw bad_optional_access("bad optional access")
+#endif
+		}
+
+# endif
+
+# if OPTIONAL_HAS_THIS_RVALUE_REFS == 1
+
+		template <class V>
+		constexpr T value_or(V&& v) const&
+		{
+			return *this ? **this : detail_::convert<T>(constexpr_forward<V>(v));
+		}
+
+#   if OPTIONAL_HAS_MOVE_ACCESSORS == 1
+
+		template <class V>
+		OPTIONAL_MUTABLE_CONSTEXPR T value_or(V&& v) &&
+		{
+			return *this ? constexpr_move(const_cast<optional<T>&>(*this).contained_val()) : detail_::convert<T>(constexpr_forward<V>(v));
+		}
+
+#   else
+
+		template <class V>
+		T value_or(V&& v) &&
+		{
+			return *this ? constexpr_move(const_cast<optional<T>&>(*this).contained_val()) : detail_::convert<T>(constexpr_forward<V>(v));
+		}
+
+#   endif
+
+# else
+
+		template <class V>
+		constexpr T value_or(V&& v) const
+		{
+			return *this ? **this : detail_::convert<T>(constexpr_forward<V>(v));
+		}
+
+# endif
+
+	};
+
+
+	template <class T>
+	class optional<T&>
+	{
+		static_assert(!::std::is_same<T, nullopt_t>::value, "bad T");
+		static_assert(!::std::is_same<T, in_place_t>::value, "bad T");
+		T* ref;
+
+	public:
+
+		// 20.5.5.1, construction/destruction
+		constexpr optional() noexcept : ref(nullptr) {}
+
+		constexpr optional(nullopt_t) noexcept : ref(nullptr) {}
+
+		constexpr optional(T& v) noexcept : ref(detail_::static_addressof(v)) {}
+
+		optional(T&&) = delete;
+
+		constexpr optional(const optional& rhs) noexcept : ref(rhs.ref) {}
+
+		explicit constexpr optional(in_place_t, T& v) noexcept : ref(detail_::static_addressof(v)) {}
+
+		explicit optional(in_place_t, T&&) = delete;
+
+		~optional() = default;
+
+		// 20.5.5.2, mutation
+		optional& operator=(nullopt_t) noexcept {
+			ref = nullptr;
+			return *this;
+		}
+
+		// optional& operator=(const optional& rhs) noexcept {
+		  // ref = rhs.ref;
+		  // return *this;
+		// }
+
+		// optional& operator=(optional&& rhs) noexcept {
+		  // ref = rhs.ref;
+		  // return *this;
+		// }
+
+		template <typename U>
+		auto operator=(U&& rhs) noexcept
+			-> typename ::std::enable_if
+			<
+			::std::is_same<typename ::std::decay<U>::type, optional<T&>>::value,
+			optional&
+			>::type
+		{
+			ref = rhs.ref;
+			return *this;
+		}
+
+		template <typename U>
+		auto operator=(U&& rhs) noexcept
+			-> typename ::std::enable_if
+			<
+			!::std::is_same<typename ::std::decay<U>::type, optional<T&>>::value,
+			optional&
+			>::type
+			= delete;
+
+		void emplace(T& v) noexcept {
+			ref = detail_::static_addressof(v);
+		}
+
+		void emplace(T&&) = delete;
+
+
+		void swap(optional<T&>& rhs) noexcept
+		{
+			::std::swap(ref, rhs.ref);
+		}
+
+		// 20.5.5.3, observers
+		constexpr T* operator->() const {
+			return TR2_OPTIONAL_ASSERTED_EXPRESSION(ref, ref);
+		}
+
+		constexpr T& operator*() const {
+			return TR2_OPTIONAL_ASSERTED_EXPRESSION(ref, *ref);
+		}
+
+		constexpr T& value() const {
+			if (ref) {
+				return *ref;
+			}
+#ifdef SOL_NO_EXCEPTIONS
+			// Can't abort in constexpr. Lovely.
+			std::abort();
+			T* noreach = (T*)nullptr;
+			return *noreach;
+#else
+			throw bad_optional_access("bad optional access")
+#endif
+		}
+
+		explicit constexpr operator bool() const noexcept {
+			return ref != nullptr;
+		}
+
+		template <typename V>
+		constexpr T& value_or(V&& v) const
+		{
+			return *this ? **this : detail_::convert<T&>(constexpr_forward<V>(v));
+		}
+	};
+
+
+	template <class T>
+	class optional<T&&>
+	{
+		static_assert(sizeof(T) == 0, "optional rvalue references disallowed");
+	};
+
+
+	// 20.5.8, Relational operators
+	template <class T> constexpr bool operator==(const optional<T>& x, const optional<T>& y)
+	{
+		return bool(x) != bool(y) ? false : bool(x) == false ? true : *x == *y;
+	}
+
+	template <class T> constexpr bool operator!=(const optional<T>& x, const optional<T>& y)
+	{
+		return !(x == y);
+	}
+
+	template <class T> constexpr bool operator<(const optional<T>& x, const optional<T>& y)
+	{
+		return (!y) ? false : (!x) ? true : *x < *y;
+	}
+
+	template <class T> constexpr bool operator>(const optional<T>& x, const optional<T>& y)
+	{
+		return (y < x);
+	}
+
+	template <class T> constexpr bool operator<=(const optional<T>& x, const optional<T>& y)
+	{
+		return !(y < x);
+	}
+
+	template <class T> constexpr bool operator>=(const optional<T>& x, const optional<T>& y)
+	{
+		return !(x < y);
+	}
+
+
+	// 20.5.9, Comparison with nullopt
+	template <class T> constexpr bool operator==(const optional<T>& x, nullopt_t) noexcept
+	{
+		return (!x);
+	}
+
+	template <class T> constexpr bool operator==(nullopt_t, const optional<T>& x) noexcept
+	{
+		return (!x);
+	}
+
+	template <class T> constexpr bool operator!=(const optional<T>& x, nullopt_t) noexcept
+	{
+		return bool(x);
+	}
+
+	template <class T> constexpr bool operator!=(nullopt_t, const optional<T>& x) noexcept
+	{
+		return bool(x);
+	}
+
+	template <class T> constexpr bool operator<(const optional<T>&, nullopt_t) noexcept
+	{
+		return false;
+	}
+
+	template <class T> constexpr bool operator<(nullopt_t, const optional<T>& x) noexcept
+	{
+		return bool(x);
+	}
+
+	template <class T> constexpr bool operator<=(const optional<T>& x, nullopt_t) noexcept
+	{
+		return (!x);
+	}
+
+	template <class T> constexpr bool operator<=(nullopt_t, const optional<T>&) noexcept
+	{
+		return true;
+	}
+
+	template <class T> constexpr bool operator>(const optional<T>& x, nullopt_t) noexcept
+	{
+		return bool(x);
+	}
+
+	template <class T> constexpr bool operator>(nullopt_t, const optional<T>&) noexcept
+	{
+		return false;
+	}
+
+	template <class T> constexpr bool operator>=(const optional<T>&, nullopt_t) noexcept
+	{
+		return true;
+	}
+
+	template <class T> constexpr bool operator>=(nullopt_t, const optional<T>& x) noexcept
+	{
+		return (!x);
+	}
+
+
+
+	// 20.5.10, Comparison with T
+	template <class T> constexpr bool operator==(const optional<T>& x, const T& v)
+	{
+		return bool(x) ? *x == v : false;
+	}
+
+	template <class T> constexpr bool operator==(const T& v, const optional<T>& x)
+	{
+		return bool(x) ? v == *x : false;
+	}
+
+	template <class T> constexpr bool operator!=(const optional<T>& x, const T& v)
+	{
+		return bool(x) ? *x != v : true;
+	}
+
+	template <class T> constexpr bool operator!=(const T& v, const optional<T>& x)
+	{
+		return bool(x) ? v != *x : true;
+	}
+
+	template <class T> constexpr bool operator<(const optional<T>& x, const T& v)
+	{
+		return bool(x) ? *x < v : true;
+	}
+
+	template <class T> constexpr bool operator>(const T& v, const optional<T>& x)
+	{
+		return bool(x) ? v > *x : true;
+	}
+
+	template <class T> constexpr bool operator>(const optional<T>& x, const T& v)
+	{
+		return bool(x) ? *x > v : false;
+	}
+
+	template <class T> constexpr bool operator<(const T& v, const optional<T>& x)
+	{
+		return bool(x) ? v < *x : false;
+	}
+
+	template <class T> constexpr bool operator>=(const optional<T>& x, const T& v)
+	{
+		return bool(x) ? *x >= v : false;
+	}
+
+	template <class T> constexpr bool operator<=(const T& v, const optional<T>& x)
+	{
+		return bool(x) ? v <= *x : false;
+	}
+
+	template <class T> constexpr bool operator<=(const optional<T>& x, const T& v)
+	{
+		return bool(x) ? *x <= v : true;
+	}
+
+	template <class T> constexpr bool operator>=(const T& v, const optional<T>& x)
+	{
+		return bool(x) ? v >= *x : true;
+	}
+
+
+	// Comparison of optional<T&> with T
+	template <class T> constexpr bool operator==(const optional<T&>& x, const T& v)
+	{
+		return bool(x) ? *x == v : false;
+	}
+
+	template <class T> constexpr bool operator==(const T& v, const optional<T&>& x)
+	{
+		return bool(x) ? v == *x : false;
+	}
+
+	template <class T> constexpr bool operator!=(const optional<T&>& x, const T& v)
+	{
+		return bool(x) ? *x != v : true;
+	}
+
+	template <class T> constexpr bool operator!=(const T& v, const optional<T&>& x)
+	{
+		return bool(x) ? v != *x : true;
+	}
+
+	template <class T> constexpr bool operator<(const optional<T&>& x, const T& v)
+	{
+		return bool(x) ? *x < v : true;
+	}
+
+	template <class T> constexpr bool operator>(const T& v, const optional<T&>& x)
+	{
+		return bool(x) ? v > *x : true;
+	}
+
+	template <class T> constexpr bool operator>(const optional<T&>& x, const T& v)
+	{
+		return bool(x) ? *x > v : false;
+	}
+
+	template <class T> constexpr bool operator<(const T& v, const optional<T&>& x)
+	{
+		return bool(x) ? v < *x : false;
+	}
+
+	template <class T> constexpr bool operator>=(const optional<T&>& x, const T& v)
+	{
+		return bool(x) ? *x >= v : false;
+	}
+
+	template <class T> constexpr bool operator<=(const T& v, const optional<T&>& x)
+	{
+		return bool(x) ? v <= *x : false;
+	}
+
+	template <class T> constexpr bool operator<=(const optional<T&>& x, const T& v)
+	{
+		return bool(x) ? *x <= v : true;
+	}
+
+	template <class T> constexpr bool operator>=(const T& v, const optional<T&>& x)
+	{
+		return bool(x) ? v >= *x : true;
+	}
+
+	// Comparison of optional<T const&> with T
+	template <class T> constexpr bool operator==(const optional<const T&>& x, const T& v)
+	{
+		return bool(x) ? *x == v : false;
+	}
+
+	template <class T> constexpr bool operator==(const T& v, const optional<const T&>& x)
+	{
+		return bool(x) ? v == *x : false;
+	}
+
+	template <class T> constexpr bool operator!=(const optional<const T&>& x, const T& v)
+	{
+		return bool(x) ? *x != v : true;
+	}
+
+	template <class T> constexpr bool operator!=(const T& v, const optional<const T&>& x)
+	{
+		return bool(x) ? v != *x : true;
+	}
+
+	template <class T> constexpr bool operator<(const optional<const T&>& x, const T& v)
+	{
+		return bool(x) ? *x < v : true;
+	}
+
+	template <class T> constexpr bool operator>(const T& v, const optional<const T&>& x)
+	{
+		return bool(x) ? v > *x : true;
+	}
+
+	template <class T> constexpr bool operator>(const optional<const T&>& x, const T& v)
+	{
+		return bool(x) ? *x > v : false;
+	}
+
+	template <class T> constexpr bool operator<(const T& v, const optional<const T&>& x)
+	{
+		return bool(x) ? v < *x : false;
+	}
+
+	template <class T> constexpr bool operator>=(const optional<const T&>& x, const T& v)
+	{
+		return bool(x) ? *x >= v : false;
+	}
+
+	template <class T> constexpr bool operator<=(const T& v, const optional<const T&>& x)
+	{
+		return bool(x) ? v <= *x : false;
+	}
+
+	template <class T> constexpr bool operator<=(const optional<const T&>& x, const T& v)
+	{
+		return bool(x) ? *x <= v : true;
+	}
+
+	template <class T> constexpr bool operator>=(const T& v, const optional<const T&>& x)
+	{
+		return bool(x) ? v >= *x : true;
+	}
+
+
+	// 20.5.12, Specialized algorithms
+	template <class T>
+	void swap(optional<T>& x, optional<T>& y) noexcept(noexcept(x.swap(y))) {
+		x.swap(y);
+	}
+
+
+	template <class T>
+	constexpr optional<typename ::std::decay<T>::type> make_optional(T&& v) {
+		return optional<typename ::std::decay<T>::type>(constexpr_forward<T>(v));
+	}
+
+	template <class X>
+	constexpr optional<X&> make_optional(::std::reference_wrapper<X> v) {
+		return optional<X&>(v.get());
+	}
+
+
+} // namespace 
+
+namespace std
+{
+	template <typename T>
+	struct hash<sol::optional<T>> {
+		typedef typename hash<T>::result_type result_type;
+		typedef sol::optional<T> argument_type;
+
+		constexpr result_type operator()(argument_type const& arg) const {
+			return arg ? ::std::hash<T>{}(*arg) : result_type{};
+		}
+	};
+
+	template <typename T>
+	struct hash<sol::optional<T&>> {
+		typedef typename hash<T>::result_type result_type;
+		typedef sol::optional<T&> argument_type;
+
+		constexpr result_type operator()(argument_type const& arg) const {
+			return arg ? ::std::hash<T>{}(*arg) : result_type{};
+		}
+	};
+}
+
+# undef TR2_OPTIONAL_REQUIRES
+# undef TR2_OPTIONAL_ASSERTED_EXPRESSION
+
+# endif //___SOL_OPTIONAL_HPP___