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authorMichael Lutz <michi@icosahedron.de>2020-05-17 23:32:01 +0200
committerMichael Lutz <michi@icosahedron.de>2020-05-21 20:02:34 +0200
commit8aef14386fc403ee631f176abf0ec86af7dcd37b (patch)
tree7cafaed2c1637e933db7bdd97fa0a621920ce3b2 /src/3rdparty
parent63ccb36ef3ecd53a503c0e9fea87f0784802af0f (diff)
downloadopenttd-8aef14386fc403ee631f176abf0ec86af7dcd37b.tar.xz
Add: Optional implementation of std::optional for pre-C++17 compilers.
Sourced from https://github.com/akrzemi1/Optional, Boost Software License, Version 1.0.
Diffstat (limited to 'src/3rdparty')
-rw-r--r--src/3rdparty/optional/LICENSE_1_0.txt23
-rw-r--r--src/3rdparty/optional/optional.hpp1066
-rw-r--r--src/3rdparty/optional/ottd_optional.h33
3 files changed, 1122 insertions, 0 deletions
diff --git a/src/3rdparty/optional/LICENSE_1_0.txt b/src/3rdparty/optional/LICENSE_1_0.txt
new file mode 100644
index 000000000..36b7cd93c
--- /dev/null
+++ b/src/3rdparty/optional/LICENSE_1_0.txt
@@ -0,0 +1,23 @@
+Boost Software License - Version 1.0 - August 17th, 2003
+
+Permission is hereby granted, free of charge, to any person or organization
+obtaining a copy of the software and accompanying documentation covered by
+this license (the "Software") to use, reproduce, display, distribute,
+execute, and transmit the Software, and to prepare derivative works of the
+Software, and to permit third-parties to whom the Software is furnished to
+do so, all subject to the following:
+
+The copyright notices in the Software and this entire statement, including
+the above license grant, this restriction and the following disclaimer,
+must be included in all copies of the Software, in whole or in part, and
+all derivative works of the Software, unless such copies or derivative
+works are solely in the form of machine-executable object code generated by
+a source language processor.
+
+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, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/src/3rdparty/optional/optional.hpp b/src/3rdparty/optional/optional.hpp
new file mode 100644
index 000000000..fe1832b2a
--- /dev/null
+++ b/src/3rdparty/optional/optional.hpp
@@ -0,0 +1,1066 @@
+// 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 ___OPTIONAL_HPP___
+# define ___OPTIONAL_HPP___
+
+# include <utility>
+# include <type_traits>
+# include <initializer_list>
+# include <cassert>
+# include <functional>
+# include <string>
+# include <stdexcept>
+
+# define TR2_OPTIONAL_REQUIRES(...) typename enable_if<__VA_ARGS__::value, bool>::type = false
+
+# if defined __GNUC__ // NOTE: GNUC is also defined for Clang
+# if (__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 std{
+
+namespace experimental{
+
+// 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 swap_ns
+{
+ using std::swap;
+
+ template <class T>
+ void adl_swap(T& t, T& u) noexcept(noexcept(swap(t, u)))
+ {
+ swap(t, u);
+ }
+
+} // namespace swap_ns
+
+} // namespace detail
+
+
+constexpr struct trivial_init_t{} trivial_init{};
+
+
+// 20.5.6, In-place construction
+constexpr struct in_place_t{} in_place{};
+
+
+// 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 logic_error {
+public:
+ explicit bad_optional_access(const string& what_arg) : logic_error{what_arg} {}
+ explicit bad_optional_access(const char* what_arg) : logic_error{what_arg} {}
+};
+
+
+template <class T>
+union storage_t
+{
+ unsigned char dummy_;
+ T value_;
+
+ constexpr storage_t( trivial_init_t ) noexcept : dummy_() {};
+
+ template <class... Args>
+ constexpr storage_t( Args&&... args ) : value_(constexpr_forward<Args>(args)...) {}
+
+ ~storage_t(){}
+};
+
+
+template <class T>
+union constexpr_storage_t
+{
+ unsigned char dummy_;
+ T value_;
+
+ constexpr constexpr_storage_t( trivial_init_t ) noexcept : dummy_() {};
+
+ template <class... Args>
+ constexpr constexpr_storage_t( Args&&... args ) : value_(constexpr_forward<Args>(args)...) {}
+
+ ~constexpr_storage_t() = default;
+};
+
+
+template <class T>
+struct optional_base
+{
+ bool init_;
+ storage_t<T> storage_;
+
+ constexpr optional_base() noexcept : init_(false), storage_(trivial_init) {};
+
+ explicit constexpr optional_base(const T& v) : init_(true), storage_(v) {}
+
+ explicit constexpr optional_base(T&& v) : init_(true), storage_(constexpr_move(v)) {}
+
+ template <class... Args> explicit optional_base(in_place_t, Args&&... args)
+ : init_(true), storage_(constexpr_forward<Args>(args)...) {}
+
+ template <class U, class... Args, TR2_OPTIONAL_REQUIRES(is_constructible<T, std::initializer_list<U>>)>
+ explicit optional_base(in_place_t, std::initializer_list<U> il, Args&&... args)
+ : init_(true), storage_(il, std::forward<Args>(args)...) {}
+
+ ~optional_base() { if (init_) storage_.value_.T::~T(); }
+};
+
+
+template <class T>
+struct constexpr_optional_base
+{
+ bool init_;
+ constexpr_storage_t<T> storage_;
+
+ constexpr constexpr_optional_base() noexcept : init_(false), storage_(trivial_init) {};
+
+ explicit constexpr constexpr_optional_base(const T& v) : init_(true), storage_(v) {}
+
+ explicit constexpr constexpr_optional_base(T&& v) : init_(true), storage_(constexpr_move(v)) {}
+
+ template <class... Args> explicit constexpr constexpr_optional_base(in_place_t, Args&&... args)
+ : init_(true), storage_(constexpr_forward<Args>(args)...) {}
+
+ template <class U, class... Args, TR2_OPTIONAL_REQUIRES(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_(il, std::forward<Args>(args)...) {}
+
+ ~constexpr_optional_base() = default;
+};
+
+template <class T>
+using OptionalBase = typename std::conditional<
+ is_trivially_destructible<T>::value, // if possible
+ constexpr_optional_base<typename std::remove_const<T>::type>, // use base with trivial destructor
+ 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_.value_); }
+ constexpr const T* dataptr() const { return detail_::static_addressof(OptionalBase<T>::storage_.value_); }
+
+# if OPTIONAL_HAS_THIS_RVALUE_REFS == 1
+ constexpr const T& contained_val() const& { return OptionalBase<T>::storage_.value_; }
+# if OPTIONAL_HAS_MOVE_ACCESSORS == 1
+ OPTIONAL_MUTABLE_CONSTEXPR T&& contained_val() && { return std::move(OptionalBase<T>::storage_.value_); }
+ OPTIONAL_MUTABLE_CONSTEXPR T& contained_val() & { return OptionalBase<T>::storage_.value_; }
+# else
+ T& contained_val() & { return OptionalBase<T>::storage_.value_; }
+ T&& contained_val() && { return std::move(OptionalBase<T>::storage_.value_); }
+# endif
+# else
+ constexpr const T& contained_val() const { return OptionalBase<T>::storage_.value_; }
+ T& contained_val() { return OptionalBase<T>::storage_.value_; }
+# 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(optional&& rhs) noexcept(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_t{}, constexpr_forward<Args>(args)...) {}
+
+ template <class U, class... Args, TR2_OPTIONAL_REQUIRES(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_t{}, 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(is_nothrow_move_assignable<T>::value && 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 enable_if
+ <
+ is_same<typename 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(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(is_nothrow_move_constructible<T>::value
+ && noexcept(detail_::swap_ns::adl_swap(declval<T&>(), 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 bool has_value() 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& {
+ return initialized() ? contained_val() : (throw bad_optional_access("bad optional access"), contained_val());
+ }
+
+ OPTIONAL_MUTABLE_CONSTEXPR T& value() & {
+ return initialized() ? contained_val() : (throw bad_optional_access("bad optional access"), contained_val());
+ }
+
+ OPTIONAL_MUTABLE_CONSTEXPR T&& value() && {
+ if (!initialized()) throw bad_optional_access("bad optional access");
+ return std::move(contained_val());
+ }
+
+# 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 {
+ return initialized() ? contained_val() : (throw bad_optional_access("bad optional access"), contained_val());
+ }
+
+ T& value() {
+ return initialized() ? contained_val() : (throw bad_optional_access("bad optional access"), contained_val());
+ }
+
+# 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
+
+ // 20.6.3.6, modifiers
+ void reset() noexcept { clear(); }
+};
+
+
+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 enable_if
+ <
+ is_same<typename decay<U>::type, optional<T&>>::value,
+ optional&
+ >::type
+ {
+ ref = rhs.ref;
+ return *this;
+ }
+
+ template <typename U>
+ auto operator=(U&& rhs) noexcept
+ -> typename enable_if
+ <
+ !is_same<typename 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 {
+ return ref ? *ref : (throw bad_optional_access("bad optional access"), *ref);
+ }
+
+ explicit constexpr operator bool() const noexcept {
+ return ref != nullptr;
+ }
+
+ constexpr bool has_value() const noexcept {
+ return ref != nullptr;
+ }
+
+ template <class V>
+ constexpr typename decay<T>::type value_or(V&& v) const
+ {
+ return *this ? **this : detail_::convert<typename decay<T>::type>(constexpr_forward<V>(v));
+ }
+
+ // x.x.x.x, modifiers
+ void reset() noexcept { ref = nullptr; }
+};
+
+
+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 decay<T>::type> make_optional(T&& v)
+{
+ return optional<typename decay<T>::type>(constexpr_forward<T>(v));
+}
+
+template <class X>
+constexpr optional<X&> make_optional(reference_wrapper<X> v)
+{
+ return optional<X&>(v.get());
+}
+
+
+} // namespace experimental
+} // namespace std
+
+namespace std
+{
+ template <typename T>
+ struct hash<std::experimental::optional<T>>
+ {
+ typedef typename hash<T>::result_type result_type;
+ typedef std::experimental::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<std::experimental::optional<T&>>
+ {
+ typedef typename hash<T>::result_type result_type;
+ typedef std::experimental::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 //___OPTIONAL_HPP___
diff --git a/src/3rdparty/optional/ottd_optional.h b/src/3rdparty/optional/ottd_optional.h
new file mode 100644
index 000000000..19b44c505
--- /dev/null
+++ b/src/3rdparty/optional/ottd_optional.h
@@ -0,0 +1,33 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file ottd_optional.h Header to select between native. */
+
+#ifndef OTTD_OPTIONAL_H
+#define OTTD_OPTIONAL_H
+
+#if defined(__has_include)
+# if __has_include(<version>)
+# include <version>
+# endif
+#endif
+
+#if (__cplusplus >= 201703L) || (defined(__cpp_lib_optional) && __cpp_lib_optional >= 201606L)
+
+/* Native std::optional. */
+#include <optional>
+namespace opt = std;
+
+#else
+
+/* No std::optional, use local copy instead. */
+#include "optional.hpp"
+namespace opt = std::experimental;
+
+#endif
+
+#endif /* OTTD_OPTIONAL_H */