1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP_TYPE_TRAITS
11#define _LIBCPP_TYPE_TRAITS
12
13/*
14    type_traits synopsis
15
16namespace std
17{
18
19    // helper class:
20    template <class T, T v> struct integral_constant;
21    typedef integral_constant<bool, true>  true_type;   // C++11
22    typedef integral_constant<bool, false> false_type;  // C++11
23
24    template <bool B>                                   // C++14
25    using bool_constant = integral_constant<bool, B>;   // C++14
26    typedef bool_constant<true> true_type;              // C++14
27    typedef bool_constant<false> false_type;            // C++14
28
29    // helper traits
30    template <bool, class T = void> struct enable_if;
31    template <bool, class T, class F> struct conditional;
32
33    // Primary classification traits:
34    template <class T> struct is_void;
35    template <class T> struct is_null_pointer;  // C++14
36    template <class T> struct is_integral;
37    template <class T> struct is_floating_point;
38    template <class T> struct is_array;
39    template <class T> struct is_pointer;
40    template <class T> struct is_lvalue_reference;
41    template <class T> struct is_rvalue_reference;
42    template <class T> struct is_member_object_pointer;
43    template <class T> struct is_member_function_pointer;
44    template <class T> struct is_enum;
45    template <class T> struct is_union;
46    template <class T> struct is_class;
47    template <class T> struct is_function;
48
49    // Secondary classification traits:
50    template <class T> struct is_reference;
51    template <class T> struct is_arithmetic;
52    template <class T> struct is_fundamental;
53    template <class T> struct is_member_pointer;
54    template <class T> struct is_scoped_enum; // C++2b
55    template <class T> struct is_scalar;
56    template <class T> struct is_object;
57    template <class T> struct is_compound;
58
59    // Const-volatile properties and transformations:
60    template <class T> struct is_const;
61    template <class T> struct is_volatile;
62    template <class T> struct remove_const;
63    template <class T> struct remove_volatile;
64    template <class T> struct remove_cv;
65    template <class T> struct add_const;
66    template <class T> struct add_volatile;
67    template <class T> struct add_cv;
68
69    // Reference transformations:
70    template <class T> struct remove_reference;
71    template <class T> struct add_lvalue_reference;
72    template <class T> struct add_rvalue_reference;
73
74    // Pointer transformations:
75    template <class T> struct remove_pointer;
76    template <class T> struct add_pointer;
77
78    template<class T> struct type_identity;                     // C++20
79    template<class T>
80      using type_identity_t = typename type_identity<T>::type;  // C++20
81
82    // Integral properties:
83    template <class T> struct is_signed;
84    template <class T> struct is_unsigned;
85    template <class T> struct make_signed;
86    template <class T> struct make_unsigned;
87
88    // Array properties and transformations:
89    template <class T> struct rank;
90    template <class T, unsigned I = 0> struct extent;
91    template <class T> struct remove_extent;
92    template <class T> struct remove_all_extents;
93
94    template <class T> struct is_bounded_array;                 // C++20
95    template <class T> struct is_unbounded_array;               // C++20
96
97    // Member introspection:
98    template <class T> struct is_pod;
99    template <class T> struct is_trivial;
100    template <class T> struct is_trivially_copyable;
101    template <class T> struct is_standard_layout;
102    template <class T> struct is_literal_type; // Deprecated in C++17; removed in C++20
103    template <class T> struct is_empty;
104    template <class T> struct is_polymorphic;
105    template <class T> struct is_abstract;
106    template <class T> struct is_final; // C++14
107    template <class T> struct is_aggregate; // C++17
108
109    template <class T, class... Args> struct is_constructible;
110    template <class T>                struct is_default_constructible;
111    template <class T>                struct is_copy_constructible;
112    template <class T>                struct is_move_constructible;
113    template <class T, class U>       struct is_assignable;
114    template <class T>                struct is_copy_assignable;
115    template <class T>                struct is_move_assignable;
116    template <class T, class U>       struct is_swappable_with;       // C++17
117    template <class T>                struct is_swappable;            // C++17
118    template <class T>                struct is_destructible;
119
120    template <class T, class... Args> struct is_trivially_constructible;
121    template <class T>                struct is_trivially_default_constructible;
122    template <class T>                struct is_trivially_copy_constructible;
123    template <class T>                struct is_trivially_move_constructible;
124    template <class T, class U>       struct is_trivially_assignable;
125    template <class T>                struct is_trivially_copy_assignable;
126    template <class T>                struct is_trivially_move_assignable;
127    template <class T>                struct is_trivially_destructible;
128
129    template <class T, class... Args> struct is_nothrow_constructible;
130    template <class T>                struct is_nothrow_default_constructible;
131    template <class T>                struct is_nothrow_copy_constructible;
132    template <class T>                struct is_nothrow_move_constructible;
133    template <class T, class U>       struct is_nothrow_assignable;
134    template <class T>                struct is_nothrow_copy_assignable;
135    template <class T>                struct is_nothrow_move_assignable;
136    template <class T, class U>       struct is_nothrow_swappable_with; // C++17
137    template <class T>                struct is_nothrow_swappable;      // C++17
138    template <class T>                struct is_nothrow_destructible;
139
140    template <class T> struct has_virtual_destructor;
141
142    template<class T> struct has_unique_object_representations;         // C++17
143
144    // Relationships between types:
145    template <class T, class U> struct is_same;
146    template <class Base, class Derived> struct is_base_of;
147
148    template <class From, class To> struct is_convertible;
149    template <typename From, typename To> struct is_nothrow_convertible;                  // C++20
150    template <typename From, typename To> inline constexpr bool is_nothrow_convertible_v; // C++20
151
152    template <class Fn, class... ArgTypes> struct is_invocable;
153    template <class R, class Fn, class... ArgTypes> struct is_invocable_r;
154
155    template <class Fn, class... ArgTypes> struct is_nothrow_invocable;
156    template <class R, class Fn, class... ArgTypes> struct is_nothrow_invocable_r;
157
158    // Alignment properties and transformations:
159    template <class T> struct alignment_of;
160    template <size_t Len, size_t Align = most_stringent_alignment_requirement>
161        struct aligned_storage;
162    template <size_t Len, class... Types> struct aligned_union;
163    template <class T> struct remove_cvref; // C++20
164
165    template <class T> struct decay;
166    template <class... T> struct common_type;
167    template <class T> struct underlying_type;
168    template <class> class result_of; // undefined; deprecated in C++17; removed in C++20
169    template <class Fn, class... ArgTypes> class result_of<Fn(ArgTypes...)>; // deprecated in C++17; removed in C++20
170    template <class Fn, class... ArgTypes> struct invoke_result;  // C++17
171
172    // const-volatile modifications:
173    template <class T>
174      using remove_const_t    = typename remove_const<T>::type;  // C++14
175    template <class T>
176      using remove_volatile_t = typename remove_volatile<T>::type;  // C++14
177    template <class T>
178      using remove_cv_t       = typename remove_cv<T>::type;  // C++14
179    template <class T>
180      using add_const_t       = typename add_const<T>::type;  // C++14
181    template <class T>
182      using add_volatile_t    = typename add_volatile<T>::type;  // C++14
183    template <class T>
184      using add_cv_t          = typename add_cv<T>::type;  // C++14
185
186    // reference modifications:
187    template <class T>
188      using remove_reference_t     = typename remove_reference<T>::type;  // C++14
189    template <class T>
190      using add_lvalue_reference_t = typename add_lvalue_reference<T>::type;  // C++14
191    template <class T>
192      using add_rvalue_reference_t = typename add_rvalue_reference<T>::type;  // C++14
193
194    // sign modifications:
195    template <class T>
196      using make_signed_t   = typename make_signed<T>::type;  // C++14
197    template <class T>
198      using make_unsigned_t = typename make_unsigned<T>::type;  // C++14
199
200    // array modifications:
201    template <class T>
202      using remove_extent_t      = typename remove_extent<T>::type;  // C++14
203    template <class T>
204      using remove_all_extents_t = typename remove_all_extents<T>::type;  // C++14
205
206    template <class T>
207      inline constexpr bool is_bounded_array_v
208        = is_bounded_array<T>::value;                                     // C++20
209      inline constexpr bool is_unbounded_array_v
210        = is_unbounded_array<T>::value;                                   // C++20
211
212    // pointer modifications:
213    template <class T>
214      using remove_pointer_t = typename remove_pointer<T>::type;  // C++14
215    template <class T>
216      using add_pointer_t    = typename add_pointer<T>::type;  // C++14
217
218    // other transformations:
219    template <size_t Len, size_t Align=default-alignment>
220      using aligned_storage_t = typename aligned_storage<Len,Align>::type;  // C++14
221    template <size_t Len, class... Types>
222      using aligned_union_t   = typename aligned_union<Len,Types...>::type;  // C++14
223    template <class T>
224      using remove_cvref_t    = typename remove_cvref<T>::type;  // C++20
225    template <class T>
226      using decay_t           = typename decay<T>::type;  // C++14
227    template <bool b, class T=void>
228      using enable_if_t       = typename enable_if<b,T>::type;  // C++14
229    template <bool b, class T, class F>
230      using conditional_t     = typename conditional<b,T,F>::type;  // C++14
231    template <class... T>
232      using common_type_t     = typename common_type<T...>::type;  // C++14
233    template <class T>
234      using underlying_type_t = typename underlying_type<T>::type;  // C++14
235    template <class T>
236      using result_of_t       = typename result_of<T>::type;  // C++14; deprecated in C++17; removed in C++20
237    template <class Fn, class... ArgTypes>
238      using invoke_result_t   = typename invoke_result<Fn, ArgTypes...>::type;  // C++17
239
240    template <class...>
241      using void_t = void;   // C++17
242
243      // See C++14 20.10.4.1, primary type categories
244      template <class T> inline constexpr bool is_void_v
245        = is_void<T>::value;                                             // C++17
246      template <class T> inline constexpr bool is_null_pointer_v
247        = is_null_pointer<T>::value;                                     // C++17
248      template <class T> inline constexpr bool is_integral_v
249        = is_integral<T>::value;                                         // C++17
250      template <class T> inline constexpr bool is_floating_point_v
251        = is_floating_point<T>::value;                                   // C++17
252      template <class T> inline constexpr bool is_array_v
253        = is_array<T>::value;                                            // C++17
254      template <class T> inline constexpr bool is_pointer_v
255        = is_pointer<T>::value;                                          // C++17
256      template <class T> inline constexpr bool is_lvalue_reference_v
257        = is_lvalue_reference<T>::value;                                 // C++17
258      template <class T> inline constexpr bool is_rvalue_reference_v
259        = is_rvalue_reference<T>::value;                                 // C++17
260      template <class T> inline constexpr bool is_member_object_pointer_v
261        = is_member_object_pointer<T>::value;                            // C++17
262      template <class T> inline constexpr bool is_member_function_pointer_v
263        = is_member_function_pointer<T>::value;                          // C++17
264      template <class T> inline constexpr bool is_enum_v
265        = is_enum<T>::value;                                             // C++17
266      template <class T> inline constexpr bool is_union_v
267        = is_union<T>::value;                                            // C++17
268      template <class T> inline constexpr bool is_class_v
269        = is_class<T>::value;                                            // C++17
270      template <class T> inline constexpr bool is_function_v
271        = is_function<T>::value;                                         // C++17
272
273      // See C++14 20.10.4.2, composite type categories
274      template <class T> inline constexpr bool is_reference_v
275        = is_reference<T>::value;                                        // C++17
276      template <class T> inline constexpr bool is_arithmetic_v
277        = is_arithmetic<T>::value;                                       // C++17
278      template <class T> inline constexpr bool is_fundamental_v
279        = is_fundamental<T>::value;                                      // C++17
280      template <class T> inline constexpr bool is_object_v
281        = is_object<T>::value;                                           // C++17
282      template <class T> inline constexpr bool is_scalar_v
283        = is_scalar<T>::value;                                           // C++17
284      template <class T> inline constexpr bool is_compound_v
285        = is_compound<T>::value;                                         // C++17
286      template <class T> inline constexpr bool is_member_pointer_v
287        = is_member_pointer<T>::value;                                   // C++17
288      template <class T> inline constexpr bool is_scoped_enum_v
289        = is_scoped_enum<T>::value;                                      // C++2b
290
291      // See C++14 20.10.4.3, type properties
292      template <class T> inline constexpr bool is_const_v
293        = is_const<T>::value;                                            // C++17
294      template <class T> inline constexpr bool is_volatile_v
295        = is_volatile<T>::value;                                         // C++17
296      template <class T> inline constexpr bool is_trivial_v
297        = is_trivial<T>::value;                                          // C++17
298      template <class T> inline constexpr bool is_trivially_copyable_v
299        = is_trivially_copyable<T>::value;                               // C++17
300      template <class T> inline constexpr bool is_standard_layout_v
301        = is_standard_layout<T>::value;                                  // C++17
302      template <class T> inline constexpr bool is_pod_v
303        = is_pod<T>::value;                                              // C++17
304      template <class T> inline constexpr bool is_literal_type_v
305        = is_literal_type<T>::value;                                     // C++17; deprecated in C++17; removed in C++20
306      template <class T> inline constexpr bool is_empty_v
307        = is_empty<T>::value;                                            // C++17
308      template <class T> inline constexpr bool is_polymorphic_v
309        = is_polymorphic<T>::value;                                      // C++17
310      template <class T> inline constexpr bool is_abstract_v
311        = is_abstract<T>::value;                                         // C++17
312      template <class T> inline constexpr bool is_final_v
313        = is_final<T>::value;                                            // C++17
314      template <class T> inline constexpr bool is_aggregate_v
315        = is_aggregate<T>::value;                                        // C++17
316      template <class T> inline constexpr bool is_signed_v
317        = is_signed<T>::value;                                           // C++17
318      template <class T> inline constexpr bool is_unsigned_v
319        = is_unsigned<T>::value;                                         // C++17
320      template <class T, class... Args> inline constexpr bool is_constructible_v
321        = is_constructible<T, Args...>::value;                           // C++17
322      template <class T> inline constexpr bool is_default_constructible_v
323        = is_default_constructible<T>::value;                            // C++17
324      template <class T> inline constexpr bool is_copy_constructible_v
325        = is_copy_constructible<T>::value;                               // C++17
326      template <class T> inline constexpr bool is_move_constructible_v
327        = is_move_constructible<T>::value;                               // C++17
328      template <class T, class U> inline constexpr bool is_assignable_v
329        = is_assignable<T, U>::value;                                    // C++17
330      template <class T> inline constexpr bool is_copy_assignable_v
331        = is_copy_assignable<T>::value;                                  // C++17
332      template <class T> inline constexpr bool is_move_assignable_v
333        = is_move_assignable<T>::value;                                  // C++17
334      template <class T, class U> inline constexpr bool is_swappable_with_v
335        = is_swappable_with<T, U>::value;                                // C++17
336      template <class T> inline constexpr bool is_swappable_v
337        = is_swappable<T>::value;                                        // C++17
338      template <class T> inline constexpr bool is_destructible_v
339        = is_destructible<T>::value;                                     // C++17
340      template <class T, class... Args> inline constexpr bool is_trivially_constructible_v
341        = is_trivially_constructible<T, Args...>::value;                 // C++17
342      template <class T> inline constexpr bool is_trivially_default_constructible_v
343        = is_trivially_default_constructible<T>::value;                  // C++17
344      template <class T> inline constexpr bool is_trivially_copy_constructible_v
345        = is_trivially_copy_constructible<T>::value;                     // C++17
346      template <class T> inline constexpr bool is_trivially_move_constructible_v
347        = is_trivially_move_constructible<T>::value;                     // C++17
348      template <class T, class U> inline constexpr bool is_trivially_assignable_v
349        = is_trivially_assignable<T, U>::value;                          // C++17
350      template <class T> inline constexpr bool is_trivially_copy_assignable_v
351        = is_trivially_copy_assignable<T>::value;                        // C++17
352      template <class T> inline constexpr bool is_trivially_move_assignable_v
353        = is_trivially_move_assignable<T>::value;                        // C++17
354      template <class T> inline constexpr bool is_trivially_destructible_v
355        = is_trivially_destructible<T>::value;                           // C++17
356      template <class T, class... Args> inline constexpr bool is_nothrow_constructible_v
357        = is_nothrow_constructible<T, Args...>::value;                   // C++17
358      template <class T> inline constexpr bool is_nothrow_default_constructible_v
359        = is_nothrow_default_constructible<T>::value;                    // C++17
360      template <class T> inline constexpr bool is_nothrow_copy_constructible_v
361        = is_nothrow_copy_constructible<T>::value;                       // C++17
362      template <class T> inline constexpr bool is_nothrow_move_constructible_v
363        = is_nothrow_move_constructible<T>::value;                       // C++17
364      template <class T, class U> inline constexpr bool is_nothrow_assignable_v
365        = is_nothrow_assignable<T, U>::value;                            // C++17
366      template <class T> inline constexpr bool is_nothrow_copy_assignable_v
367        = is_nothrow_copy_assignable<T>::value;                          // C++17
368      template <class T> inline constexpr bool is_nothrow_move_assignable_v
369        = is_nothrow_move_assignable<T>::value;                          // C++17
370      template <class T, class U> inline constexpr bool is_nothrow_swappable_with_v
371        = is_nothrow_swappable_with<T, U>::value;                       // C++17
372      template <class T> inline constexpr bool is_nothrow_swappable_v
373        = is_nothrow_swappable<T>::value;                               // C++17
374      template <class T> inline constexpr bool is_nothrow_destructible_v
375        = is_nothrow_destructible<T>::value;                             // C++17
376      template <class T> inline constexpr bool has_virtual_destructor_v
377        = has_virtual_destructor<T>::value;                              // C++17
378      template<class T> inline constexpr bool has_unique_object_representations_v // C++17
379        = has_unique_object_representations<T>::value;
380
381      // See C++14 20.10.5, type property queries
382      template <class T> inline constexpr size_t alignment_of_v
383        = alignment_of<T>::value;                                        // C++17
384      template <class T> inline constexpr size_t rank_v
385        = rank<T>::value;                                                // C++17
386      template <class T, unsigned I = 0> inline constexpr size_t extent_v
387        = extent<T, I>::value;                                           // C++17
388
389      // See C++14 20.10.6, type relations
390      template <class T, class U> inline constexpr bool is_same_v
391        = is_same<T, U>::value;                                          // C++17
392      template <class Base, class Derived> inline constexpr bool is_base_of_v
393        = is_base_of<Base, Derived>::value;                              // C++17
394      template <class From, class To> inline constexpr bool is_convertible_v
395        = is_convertible<From, To>::value;                               // C++17
396      template <class Fn, class... ArgTypes> inline constexpr bool is_invocable_v
397        = is_invocable<Fn, ArgTypes...>::value;                          // C++17
398      template <class R, class Fn, class... ArgTypes> inline constexpr bool is_invocable_r_v
399        = is_invocable_r<R, Fn, ArgTypes...>::value;                     // C++17
400      template <class Fn, class... ArgTypes> inline constexpr bool is_nothrow_invocable_v
401        = is_nothrow_invocable<Fn, ArgTypes...>::value;                  // C++17
402      template <class R, class Fn, class... ArgTypes> inline constexpr bool is_nothrow_invocable_r_v
403        = is_nothrow_invocable_r<R, Fn, ArgTypes...>::value;             // C++17
404
405      // [meta.logical], logical operator traits:
406      template<class... B> struct conjunction;                           // C++17
407      template<class... B>
408        inline constexpr bool conjunction_v = conjunction<B...>::value;  // C++17
409      template<class... B> struct disjunction;                           // C++17
410      template<class... B>
411        inline constexpr bool disjunction_v = disjunction<B...>::value;  // C++17
412      template<class B> struct negation;                                 // C++17
413      template<class B>
414        inline constexpr bool negation_v = negation<B>::value;           // C++17
415
416}
417
418*/
419#include <__assert> // all public C++ headers provide the assertion handler
420#include <__config>
421#include <__functional/invoke.h>
422#include <__type_traits/add_const.h>
423#include <__type_traits/add_cv.h>
424#include <__type_traits/add_lvalue_reference.h>
425#include <__type_traits/add_pointer.h>
426#include <__type_traits/add_rvalue_reference.h>
427#include <__type_traits/add_volatile.h>
428#include <__type_traits/alignment_of.h>
429#include <__type_traits/apply_cv.h>
430#include <__type_traits/conditional.h>
431#include <__type_traits/conjunction.h>
432#include <__type_traits/decay.h>
433#include <__type_traits/disjunction.h>
434#include <__type_traits/enable_if.h>
435#include <__type_traits/extent.h>
436#include <__type_traits/has_unique_object_representation.h>
437#include <__type_traits/has_virtual_destructor.h>
438#include <__type_traits/integral_constant.h>
439#include <__type_traits/is_abstract.h>
440#include <__type_traits/is_aggregate.h>
441#include <__type_traits/is_arithmetic.h>
442#include <__type_traits/is_array.h>
443#include <__type_traits/is_assignable.h>
444#include <__type_traits/is_base_of.h>
445#include <__type_traits/is_bounded_array.h>
446#include <__type_traits/is_callable.h>
447#include <__type_traits/is_class.h>
448#include <__type_traits/is_compound.h>
449#include <__type_traits/is_const.h>
450#include <__type_traits/is_constant_evaluated.h>
451#include <__type_traits/is_constructible.h>
452#include <__type_traits/is_convertible.h>
453#include <__type_traits/is_copy_assignable.h>
454#include <__type_traits/is_copy_constructible.h>
455#include <__type_traits/is_default_constructible.h>
456#include <__type_traits/is_destructible.h>
457#include <__type_traits/is_empty.h>
458#include <__type_traits/is_enum.h>
459#include <__type_traits/is_final.h>
460#include <__type_traits/is_floating_point.h>
461#include <__type_traits/is_function.h>
462#include <__type_traits/is_fundamental.h>
463#include <__type_traits/is_integral.h>
464#include <__type_traits/is_literal_type.h>
465#include <__type_traits/is_member_function_pointer.h>
466#include <__type_traits/is_member_object_pointer.h>
467#include <__type_traits/is_member_pointer.h>
468#include <__type_traits/is_move_assignable.h>
469#include <__type_traits/is_move_constructible.h>
470#include <__type_traits/is_nothrow_assignable.h>
471#include <__type_traits/is_nothrow_constructible.h>
472#include <__type_traits/is_nothrow_copy_assignable.h>
473#include <__type_traits/is_nothrow_copy_constructible.h>
474#include <__type_traits/is_nothrow_default_constructible.h>
475#include <__type_traits/is_nothrow_destructible.h>
476#include <__type_traits/is_nothrow_move_assignable.h>
477#include <__type_traits/is_nothrow_move_constructible.h>
478#include <__type_traits/is_null_pointer.h>
479#include <__type_traits/is_object.h>
480#include <__type_traits/is_pod.h>
481#include <__type_traits/is_pointer.h>
482#include <__type_traits/is_polymorphic.h>
483#include <__type_traits/is_reference.h>
484#include <__type_traits/is_reference_wrapper.h>
485#include <__type_traits/is_referenceable.h>
486#include <__type_traits/is_same.h>
487#include <__type_traits/is_scalar.h>
488#include <__type_traits/is_scoped_enum.h>
489#include <__type_traits/is_signed.h>
490#include <__type_traits/is_standard_layout.h>
491#include <__type_traits/is_trivial.h>
492#include <__type_traits/is_trivially_assignable.h>
493#include <__type_traits/is_trivially_constructible.h>
494#include <__type_traits/is_trivially_copy_assignable.h>
495#include <__type_traits/is_trivially_copy_constructible.h>
496#include <__type_traits/is_trivially_copyable.h>
497#include <__type_traits/is_trivially_default_constructible.h>
498#include <__type_traits/is_trivially_destructible.h>
499#include <__type_traits/is_trivially_move_assignable.h>
500#include <__type_traits/is_trivially_move_constructible.h>
501#include <__type_traits/is_unbounded_array.h>
502#include <__type_traits/is_union.h>
503#include <__type_traits/is_unsigned.h>
504#include <__type_traits/is_void.h>
505#include <__type_traits/is_volatile.h>
506#include <__type_traits/negation.h>
507#include <__type_traits/rank.h>
508#include <__type_traits/remove_all_extents.h>
509#include <__type_traits/remove_const.h>
510#include <__type_traits/remove_cv.h>
511#include <__type_traits/remove_extent.h>
512#include <__type_traits/remove_pointer.h>
513#include <__type_traits/remove_reference.h>
514#include <__type_traits/remove_volatile.h>
515#include <__type_traits/type_identity.h>
516#include <__type_traits/underlying_type.h>
517#include <__type_traits/void_t.h>
518#include <__utility/declval.h>
519#include <cstddef>
520#include <cstdint>
521#include <version>
522
523#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
524#  pragma GCC system_header
525#endif
526
527_LIBCPP_BEGIN_NAMESPACE_STD
528
529template <class _T1, class _T2> struct _LIBCPP_TEMPLATE_VIS pair;
530template <class _Tp> struct _LIBCPP_TEMPLATE_VIS hash;
531
532template <bool> struct _MetaBase;
533template <>
534struct _MetaBase<true> {
535  template <class _Tp, class _Up>
536  using _SelectImpl _LIBCPP_NODEBUG = _Tp;
537  template <template <class...> class _FirstFn, template <class...> class, class ..._Args>
538  using _SelectApplyImpl _LIBCPP_NODEBUG = _FirstFn<_Args...>;
539  template <class _First, class...>
540  using _FirstImpl _LIBCPP_NODEBUG = _First;
541  template <class, class _Second, class...>
542  using _SecondImpl _LIBCPP_NODEBUG = _Second;
543  template <class _Result, class _First, class ..._Rest>
544  using _OrImpl _LIBCPP_NODEBUG = typename _MetaBase<_First::value != true && sizeof...(_Rest) != 0>::template _OrImpl<_First, _Rest...>;
545};
546
547template <>
548struct _MetaBase<false> {
549  template <class _Tp, class _Up>
550  using _SelectImpl _LIBCPP_NODEBUG = _Up;
551  template <template <class...> class, template <class...> class _SecondFn, class ..._Args>
552  using _SelectApplyImpl _LIBCPP_NODEBUG = _SecondFn<_Args...>;
553  template <class _Result, class ...>
554  using _OrImpl _LIBCPP_NODEBUG = _Result;
555};
556template <bool _Cond, class _IfRes, class _ElseRes>
557using _If _LIBCPP_NODEBUG = typename _MetaBase<_Cond>::template _SelectImpl<_IfRes, _ElseRes>;
558template <class ..._Rest>
559using _Or _LIBCPP_NODEBUG = typename _MetaBase< sizeof...(_Rest) != 0 >::template _OrImpl<false_type, _Rest...>;
560template <class ..._Args>
561using _FirstType _LIBCPP_NODEBUG = typename _MetaBase<(sizeof...(_Args) >= 1)>::template _FirstImpl<_Args...>;
562template <class ..._Args>
563using _SecondType _LIBCPP_NODEBUG = typename _MetaBase<(sizeof...(_Args) >= 2)>::template _SecondImpl<_Args...>;
564
565template <class ...> using __expand_to_true = true_type;
566template <class ..._Pred>
567__expand_to_true<__enable_if_t<_Pred::value>...> __and_helper(int);
568template <class ...>
569false_type __and_helper(...);
570template <class ..._Pred>
571using _And _LIBCPP_NODEBUG = decltype(__and_helper<_Pred...>(0));
572
573template <template <class...> class _Func, class ..._Args>
574struct _Lazy : _Func<_Args...> {};
575
576// Member detector base
577
578template <template <class...> class _Templ, class ..._Args, class = _Templ<_Args...> >
579true_type __sfinae_test_impl(int);
580template <template <class...> class, class ...>
581false_type __sfinae_test_impl(...);
582
583template <template <class ...> class _Templ, class ..._Args>
584using _IsValidExpansion _LIBCPP_NODEBUG = decltype(__sfinae_test_impl<_Templ, _Args...>(0));
585
586template <class _Tp, bool>
587struct _LIBCPP_TEMPLATE_VIS __dependent_type : public _Tp {};
588
589// is_same
590
591template <class _Tp>
592using __test_for_primary_template = __enable_if_t<
593    _IsSame<_Tp, typename _Tp::__primary_template>::value
594  >;
595template <class _Tp>
596using __is_primary_template = _IsValidExpansion<
597    __test_for_primary_template, _Tp
598  >;
599
600// is_integral
601
602// [basic.fundamental] defines five standard signed integer types;
603// __int128_t is an extended signed integer type.
604// The signed and unsigned integer types, plus bool and the
605// five types with "char" in their name, compose the "integral" types.
606
607template <class _Tp> struct __libcpp_is_signed_integer : public false_type {};
608template <> struct __libcpp_is_signed_integer<signed char>      : public true_type {};
609template <> struct __libcpp_is_signed_integer<signed short>     : public true_type {};
610template <> struct __libcpp_is_signed_integer<signed int>       : public true_type {};
611template <> struct __libcpp_is_signed_integer<signed long>      : public true_type {};
612template <> struct __libcpp_is_signed_integer<signed long long> : public true_type {};
613#ifndef _LIBCPP_HAS_NO_INT128
614template <> struct __libcpp_is_signed_integer<__int128_t>       : public true_type {};
615#endif
616
617template <class _Tp> struct __libcpp_is_unsigned_integer : public false_type {};
618template <> struct __libcpp_is_unsigned_integer<unsigned char>      : public true_type {};
619template <> struct __libcpp_is_unsigned_integer<unsigned short>     : public true_type {};
620template <> struct __libcpp_is_unsigned_integer<unsigned int>       : public true_type {};
621template <> struct __libcpp_is_unsigned_integer<unsigned long>      : public true_type {};
622template <> struct __libcpp_is_unsigned_integer<unsigned long long> : public true_type {};
623#ifndef _LIBCPP_HAS_NO_INT128
624template <> struct __libcpp_is_unsigned_integer<__uint128_t>        : public true_type {};
625#endif
626
627template <class _Tp>
628struct __unconstref {
629    typedef _LIBCPP_NODEBUG typename remove_const<typename remove_reference<_Tp>::type>::type type;
630};
631
632template <class _Tp>
633using __uncvref_t _LIBCPP_NODEBUG = typename remove_cv<typename remove_reference<_Tp>::type>::type;
634
635// __is_same_uncvref
636
637template <class _Tp, class _Up>
638struct __is_same_uncvref : _IsSame<__uncvref_t<_Tp>, __uncvref_t<_Up> > {};
639
640#if _LIBCPP_STD_VER > 17
641// remove_cvref - same as __uncvref
642template <class _Tp>
643struct remove_cvref {
644    using type _LIBCPP_NODEBUG = __uncvref_t<_Tp>;
645};
646
647template <class _Tp> using remove_cvref_t = typename remove_cvref<_Tp>::type;
648#endif
649
650// is_nothrow_convertible
651
652#if _LIBCPP_STD_VER > 17
653
654template <typename _Tp>
655static void __test_noexcept(_Tp) noexcept;
656
657template<typename _Fm, typename _To>
658static bool_constant<noexcept(_VSTD::__test_noexcept<_To>(declval<_Fm>()))>
659__is_nothrow_convertible_test();
660
661template <typename _Fm, typename _To>
662struct __is_nothrow_convertible_helper: decltype(__is_nothrow_convertible_test<_Fm, _To>())
663{ };
664
665template <typename _Fm, typename _To>
666struct is_nothrow_convertible : _Or<
667    _And<is_void<_To>, is_void<_Fm>>,
668    _Lazy<_And, is_convertible<_Fm, _To>, __is_nothrow_convertible_helper<_Fm, _To>>
669>::type { };
670
671template <typename _Fm, typename _To>
672inline constexpr bool is_nothrow_convertible_v = is_nothrow_convertible<_Fm, _To>::value;
673
674#endif // _LIBCPP_STD_VER > 17
675
676// aligned_storage
677
678template <class _Hp, class _Tp>
679struct __type_list
680{
681    typedef _Hp _Head;
682    typedef _Tp _Tail;
683};
684
685template <class _Tp>
686struct __align_type
687{
688    static const size_t value = _LIBCPP_PREFERRED_ALIGNOF(_Tp);
689    typedef _Tp type;
690};
691
692struct __struct_double {long double __lx;};
693struct __struct_double4 {double __lx[4];};
694
695typedef
696    __type_list<__align_type<unsigned char>,
697    __type_list<__align_type<unsigned short>,
698    __type_list<__align_type<unsigned int>,
699    __type_list<__align_type<unsigned long>,
700    __type_list<__align_type<unsigned long long>,
701    __type_list<__align_type<double>,
702    __type_list<__align_type<long double>,
703    __type_list<__align_type<__struct_double>,
704    __type_list<__align_type<__struct_double4>,
705    __type_list<__align_type<int*>,
706    __nat
707    > > > > > > > > > > __all_types;
708
709template <size_t _Align>
710struct _ALIGNAS(_Align) __fallback_overaligned {};
711
712template <class _TL, size_t _Align> struct __find_pod;
713
714template <class _Hp, size_t _Align>
715struct __find_pod<__type_list<_Hp, __nat>, _Align>
716{
717    typedef typename conditional<
718                             _Align == _Hp::value,
719                             typename _Hp::type,
720                             __fallback_overaligned<_Align>
721                         >::type type;
722};
723
724template <class _Hp, class _Tp, size_t _Align>
725struct __find_pod<__type_list<_Hp, _Tp>, _Align>
726{
727    typedef typename conditional<
728                             _Align == _Hp::value,
729                             typename _Hp::type,
730                             typename __find_pod<_Tp, _Align>::type
731                         >::type type;
732};
733
734template <class _TL, size_t _Len> struct __find_max_align;
735
736template <class _Hp, size_t _Len>
737struct __find_max_align<__type_list<_Hp, __nat>, _Len> : public integral_constant<size_t, _Hp::value> {};
738
739template <size_t _Len, size_t _A1, size_t _A2>
740struct __select_align
741{
742private:
743    static const size_t __min = _A2 < _A1 ? _A2 : _A1;
744    static const size_t __max = _A1 < _A2 ? _A2 : _A1;
745public:
746    static const size_t value = _Len < __max ? __min : __max;
747};
748
749template <class _Hp, class _Tp, size_t _Len>
750struct __find_max_align<__type_list<_Hp, _Tp>, _Len>
751    : public integral_constant<size_t, __select_align<_Len, _Hp::value, __find_max_align<_Tp, _Len>::value>::value> {};
752
753template <size_t _Len, size_t _Align = __find_max_align<__all_types, _Len>::value>
754struct _LIBCPP_TEMPLATE_VIS aligned_storage
755{
756    typedef typename __find_pod<__all_types, _Align>::type _Aligner;
757    union type
758    {
759        _Aligner __align;
760        unsigned char __data[(_Len + _Align - 1)/_Align * _Align];
761    };
762};
763
764#if _LIBCPP_STD_VER > 11
765template <size_t _Len, size_t _Align = __find_max_align<__all_types, _Len>::value>
766    using aligned_storage_t = typename aligned_storage<_Len, _Align>::type;
767#endif
768
769#define _CREATE_ALIGNED_STORAGE_SPECIALIZATION(n) \
770template <size_t _Len>\
771struct _LIBCPP_TEMPLATE_VIS aligned_storage<_Len, n>\
772{\
773    struct _ALIGNAS(n) type\
774    {\
775        unsigned char __lx[(_Len + n - 1)/n * n];\
776    };\
777}
778
779_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x1);
780_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x2);
781_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x4);
782_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x8);
783_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x10);
784_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x20);
785_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x40);
786_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x80);
787_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x100);
788_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x200);
789_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x400);
790_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x800);
791_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x1000);
792_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x2000);
793// PE/COFF does not support alignment beyond 8192 (=0x2000)
794#if !defined(_LIBCPP_OBJECT_FORMAT_COFF)
795_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x4000);
796#endif // !defined(_LIBCPP_OBJECT_FORMAT_COFF)
797
798#undef _CREATE_ALIGNED_STORAGE_SPECIALIZATION
799
800
801// aligned_union
802
803template <size_t _I0, size_t ..._In>
804struct __static_max;
805
806template <size_t _I0>
807struct __static_max<_I0>
808{
809    static const size_t value = _I0;
810};
811
812template <size_t _I0, size_t _I1, size_t ..._In>
813struct __static_max<_I0, _I1, _In...>
814{
815    static const size_t value = _I0 >= _I1 ? __static_max<_I0, _In...>::value :
816                                             __static_max<_I1, _In...>::value;
817};
818
819template <size_t _Len, class _Type0, class ..._Types>
820struct aligned_union
821{
822    static const size_t alignment_value = __static_max<_LIBCPP_PREFERRED_ALIGNOF(_Type0),
823                                                       _LIBCPP_PREFERRED_ALIGNOF(_Types)...>::value;
824    static const size_t __len = __static_max<_Len, sizeof(_Type0),
825                                             sizeof(_Types)...>::value;
826    typedef typename aligned_storage<__len, alignment_value>::type type;
827};
828
829#if _LIBCPP_STD_VER > 11
830template <size_t _Len, class ..._Types> using aligned_union_t = typename aligned_union<_Len, _Types...>::type;
831#endif
832
833template <class _Tp>
834struct __numeric_type
835{
836   static void __test(...);
837   static float __test(float);
838   static double __test(char);
839   static double __test(int);
840   static double __test(unsigned);
841   static double __test(long);
842   static double __test(unsigned long);
843   static double __test(long long);
844   static double __test(unsigned long long);
845   static double __test(double);
846   static long double __test(long double);
847
848   typedef decltype(__test(declval<_Tp>())) type;
849   static const bool value = _IsNotSame<type, void>::value;
850};
851
852template <>
853struct __numeric_type<void>
854{
855   static const bool value = true;
856};
857
858// __promote
859
860template <class _A1, class _A2 = void, class _A3 = void,
861          bool = __numeric_type<_A1>::value &&
862                 __numeric_type<_A2>::value &&
863                 __numeric_type<_A3>::value>
864class __promote_imp
865{
866public:
867    static const bool value = false;
868};
869
870template <class _A1, class _A2, class _A3>
871class __promote_imp<_A1, _A2, _A3, true>
872{
873private:
874    typedef typename __promote_imp<_A1>::type __type1;
875    typedef typename __promote_imp<_A2>::type __type2;
876    typedef typename __promote_imp<_A3>::type __type3;
877public:
878    typedef decltype(__type1() + __type2() + __type3()) type;
879    static const bool value = true;
880};
881
882template <class _A1, class _A2>
883class __promote_imp<_A1, _A2, void, true>
884{
885private:
886    typedef typename __promote_imp<_A1>::type __type1;
887    typedef typename __promote_imp<_A2>::type __type2;
888public:
889    typedef decltype(__type1() + __type2()) type;
890    static const bool value = true;
891};
892
893template <class _A1>
894class __promote_imp<_A1, void, void, true>
895{
896public:
897    typedef typename __numeric_type<_A1>::type type;
898    static const bool value = true;
899};
900
901template <class _A1, class _A2 = void, class _A3 = void>
902class __promote : public __promote_imp<_A1, _A2, _A3> {};
903
904// make_signed / make_unsigned
905
906typedef
907    __type_list<signed char,
908    __type_list<signed short,
909    __type_list<signed int,
910    __type_list<signed long,
911    __type_list<signed long long,
912#ifndef _LIBCPP_HAS_NO_INT128
913    __type_list<__int128_t,
914#endif
915    __nat
916#ifndef _LIBCPP_HAS_NO_INT128
917    >
918#endif
919    > > > > > __signed_types;
920
921typedef
922    __type_list<unsigned char,
923    __type_list<unsigned short,
924    __type_list<unsigned int,
925    __type_list<unsigned long,
926    __type_list<unsigned long long,
927#ifndef _LIBCPP_HAS_NO_INT128
928    __type_list<__uint128_t,
929#endif
930    __nat
931#ifndef _LIBCPP_HAS_NO_INT128
932    >
933#endif
934    > > > > > __unsigned_types;
935
936template <class _TypeList, size_t _Size, bool = _Size <= sizeof(typename _TypeList::_Head)> struct __find_first;
937
938template <class _Hp, class _Tp, size_t _Size>
939struct __find_first<__type_list<_Hp, _Tp>, _Size, true>
940{
941    typedef _LIBCPP_NODEBUG _Hp type;
942};
943
944template <class _Hp, class _Tp, size_t _Size>
945struct __find_first<__type_list<_Hp, _Tp>, _Size, false>
946{
947    typedef _LIBCPP_NODEBUG typename __find_first<_Tp, _Size>::type type;
948};
949
950template <class _Tp, bool = is_integral<_Tp>::value || is_enum<_Tp>::value>
951struct __make_signed {};
952
953template <class _Tp>
954struct __make_signed<_Tp, true>
955{
956    typedef typename __find_first<__signed_types, sizeof(_Tp)>::type type;
957};
958
959template <> struct __make_signed<bool,               true> {};
960template <> struct __make_signed<  signed short,     true> {typedef short     type;};
961template <> struct __make_signed<unsigned short,     true> {typedef short     type;};
962template <> struct __make_signed<  signed int,       true> {typedef int       type;};
963template <> struct __make_signed<unsigned int,       true> {typedef int       type;};
964template <> struct __make_signed<  signed long,      true> {typedef long      type;};
965template <> struct __make_signed<unsigned long,      true> {typedef long      type;};
966template <> struct __make_signed<  signed long long, true> {typedef long long type;};
967template <> struct __make_signed<unsigned long long, true> {typedef long long type;};
968#ifndef _LIBCPP_HAS_NO_INT128
969template <> struct __make_signed<__int128_t,         true> {typedef __int128_t type;};
970template <> struct __make_signed<__uint128_t,        true> {typedef __int128_t type;};
971#endif
972
973template <class _Tp>
974struct _LIBCPP_TEMPLATE_VIS make_signed
975{
976    typedef typename __apply_cv<_Tp, typename __make_signed<typename remove_cv<_Tp>::type>::type>::type type;
977};
978
979#if _LIBCPP_STD_VER > 11
980template <class _Tp> using make_signed_t = typename make_signed<_Tp>::type;
981#endif
982
983template <class _Tp, bool = is_integral<_Tp>::value || is_enum<_Tp>::value>
984struct __make_unsigned {};
985
986template <class _Tp>
987struct __make_unsigned<_Tp, true>
988{
989    typedef typename __find_first<__unsigned_types, sizeof(_Tp)>::type type;
990};
991
992template <> struct __make_unsigned<bool,               true> {};
993template <> struct __make_unsigned<  signed short,     true> {typedef unsigned short     type;};
994template <> struct __make_unsigned<unsigned short,     true> {typedef unsigned short     type;};
995template <> struct __make_unsigned<  signed int,       true> {typedef unsigned int       type;};
996template <> struct __make_unsigned<unsigned int,       true> {typedef unsigned int       type;};
997template <> struct __make_unsigned<  signed long,      true> {typedef unsigned long      type;};
998template <> struct __make_unsigned<unsigned long,      true> {typedef unsigned long      type;};
999template <> struct __make_unsigned<  signed long long, true> {typedef unsigned long long type;};
1000template <> struct __make_unsigned<unsigned long long, true> {typedef unsigned long long type;};
1001#ifndef _LIBCPP_HAS_NO_INT128
1002template <> struct __make_unsigned<__int128_t,         true> {typedef __uint128_t        type;};
1003template <> struct __make_unsigned<__uint128_t,        true> {typedef __uint128_t        type;};
1004#endif
1005
1006template <class _Tp>
1007struct _LIBCPP_TEMPLATE_VIS make_unsigned
1008{
1009    typedef typename __apply_cv<_Tp, typename __make_unsigned<typename remove_cv<_Tp>::type>::type>::type type;
1010};
1011
1012#if _LIBCPP_STD_VER > 11
1013template <class _Tp> using make_unsigned_t = typename make_unsigned<_Tp>::type;
1014#endif
1015
1016#ifndef _LIBCPP_CXX03_LANG
1017template <class _Tp>
1018_LIBCPP_HIDE_FROM_ABI constexpr
1019typename make_unsigned<_Tp>::type __to_unsigned_like(_Tp __x) noexcept {
1020    return static_cast<typename make_unsigned<_Tp>::type>(__x);
1021}
1022#endif
1023
1024template <class _Tp, class _Up>
1025using __copy_unsigned_t = __conditional_t<is_unsigned<_Tp>::value, typename make_unsigned<_Up>::type, _Up>;
1026
1027/// Helper to promote an integral to smallest 32, 64, or 128 bit representation.
1028///
1029/// The restriction is the same as the integral version of to_char.
1030template <class _Tp>
1031#if _LIBCPP_STD_VER > 17
1032  requires (is_signed_v<_Tp> || is_unsigned_v<_Tp> || is_same_v<_Tp, char>)
1033#endif
1034using __make_32_64_or_128_bit_t =
1035  __copy_unsigned_t<_Tp,
1036    __conditional_t<sizeof(_Tp) <= sizeof(int32_t),    int32_t,
1037    __conditional_t<sizeof(_Tp) <= sizeof(int64_t),    int64_t,
1038#ifndef _LIBCPP_HAS_NO_INT128
1039    __conditional_t<sizeof(_Tp) <= sizeof(__int128_t), __int128_t,
1040    /* else */                                         void>
1041#else
1042    /* else */                                         void
1043#endif
1044    > >
1045  >;
1046
1047#if _LIBCPP_STD_VER > 17
1048// Let COND_RES(X, Y) be:
1049template <class _Tp, class _Up>
1050using __cond_type = decltype(false ? declval<_Tp>() : declval<_Up>());
1051
1052template <class _Tp, class _Up, class = void>
1053struct __common_type3 {};
1054
1055// sub-bullet 4 - "if COND_RES(CREF(D1), CREF(D2)) denotes a type..."
1056template <class _Tp, class _Up>
1057struct __common_type3<_Tp, _Up, void_t<__cond_type<const _Tp&, const _Up&>>>
1058{
1059    using type = remove_cvref_t<__cond_type<const _Tp&, const _Up&>>;
1060};
1061
1062template <class _Tp, class _Up, class = void>
1063struct __common_type2_imp : __common_type3<_Tp, _Up> {};
1064#else
1065template <class _Tp, class _Up, class = void>
1066struct __common_type2_imp {};
1067#endif
1068
1069// sub-bullet 3 - "if decay_t<decltype(false ? declval<D1>() : declval<D2>())> ..."
1070template <class _Tp, class _Up>
1071struct __common_type2_imp<_Tp, _Up,
1072                          typename __void_t<decltype(
1073                                            true ? declval<_Tp>() : declval<_Up>()
1074                                            )>::type>
1075{
1076  typedef _LIBCPP_NODEBUG typename decay<decltype(
1077                         true ? declval<_Tp>() : declval<_Up>()
1078                         )>::type type;
1079};
1080
1081template <class, class = void>
1082struct __common_type_impl {};
1083
1084// Clang provides variadic templates in C++03 as an extension.
1085#if !defined(_LIBCPP_CXX03_LANG) || defined(__clang__)
1086# define _LIBCPP_OPTIONAL_PACK(...) , __VA_ARGS__
1087template <class... _Tp>
1088struct __common_types;
1089template <class... _Tp>
1090struct _LIBCPP_TEMPLATE_VIS common_type;
1091#else
1092# define _LIBCPP_OPTIONAL_PACK(...)
1093struct __no_arg;
1094template <class _Tp, class _Up, class = __no_arg>
1095struct __common_types;
1096template <class _Tp = __no_arg, class _Up = __no_arg, class _Vp = __no_arg,
1097          class _Unused = __no_arg>
1098struct common_type {
1099  static_assert(sizeof(_Unused) == 0,
1100                "common_type accepts at most 3 arguments in C++03");
1101};
1102#endif // _LIBCPP_CXX03_LANG
1103
1104template <class _Tp, class _Up>
1105struct __common_type_impl<
1106    __common_types<_Tp, _Up>,
1107    typename __void_t<typename common_type<_Tp, _Up>::type>::type>
1108{
1109  typedef typename common_type<_Tp, _Up>::type type;
1110};
1111
1112template <class _Tp, class _Up, class _Vp _LIBCPP_OPTIONAL_PACK(class... _Rest)>
1113struct __common_type_impl<
1114    __common_types<_Tp, _Up, _Vp _LIBCPP_OPTIONAL_PACK(_Rest...)>,
1115    typename __void_t<typename common_type<_Tp, _Up>::type>::type>
1116    : __common_type_impl<__common_types<typename common_type<_Tp, _Up>::type,
1117                                        _Vp _LIBCPP_OPTIONAL_PACK(_Rest...)> > {
1118};
1119
1120// bullet 1 - sizeof...(Tp) == 0
1121
1122template <>
1123struct _LIBCPP_TEMPLATE_VIS common_type<> {};
1124
1125// bullet 2 - sizeof...(Tp) == 1
1126
1127template <class _Tp>
1128struct _LIBCPP_TEMPLATE_VIS common_type<_Tp>
1129    : public common_type<_Tp, _Tp> {};
1130
1131// bullet 3 - sizeof...(Tp) == 2
1132
1133// sub-bullet 1 - "If is_same_v<T1, D1> is false or ..."
1134template <class _Tp, class _Up>
1135struct _LIBCPP_TEMPLATE_VIS common_type<_Tp, _Up>
1136    : conditional<
1137        _IsSame<_Tp, typename decay<_Tp>::type>::value && _IsSame<_Up, typename decay<_Up>::type>::value,
1138        __common_type2_imp<_Tp, _Up>,
1139        common_type<typename decay<_Tp>::type, typename decay<_Up>::type>
1140    >::type
1141{};
1142
1143// bullet 4 - sizeof...(Tp) > 2
1144
1145template <class _Tp, class _Up, class _Vp _LIBCPP_OPTIONAL_PACK(class... _Rest)>
1146struct _LIBCPP_TEMPLATE_VIS
1147    common_type<_Tp, _Up, _Vp _LIBCPP_OPTIONAL_PACK(_Rest...)>
1148    : __common_type_impl<
1149          __common_types<_Tp, _Up, _Vp _LIBCPP_OPTIONAL_PACK(_Rest...)> > {};
1150
1151#undef _LIBCPP_OPTIONAL_PACK
1152
1153#if _LIBCPP_STD_VER > 11
1154template <class ..._Tp> using common_type_t = typename common_type<_Tp...>::type;
1155#endif
1156
1157#if _LIBCPP_STD_VER > 11
1158// Let COPYCV(FROM, TO) be an alias for type TO with the addition of FROM's
1159// top-level cv-qualifiers.
1160template <class _From, class _To>
1161struct __copy_cv
1162{
1163    using type = _To;
1164};
1165
1166template <class _From, class _To>
1167struct __copy_cv<const _From, _To>
1168{
1169    using type = add_const_t<_To>;
1170};
1171
1172template <class _From, class _To>
1173struct __copy_cv<volatile _From, _To>
1174{
1175    using type = add_volatile_t<_To>;
1176};
1177
1178template <class _From, class _To>
1179struct __copy_cv<const volatile _From, _To>
1180{
1181    using type = add_cv_t<_To>;
1182};
1183
1184template <class _From, class _To>
1185using __copy_cv_t = typename __copy_cv<_From, _To>::type;
1186
1187template <class _From, class _To>
1188struct __copy_cvref
1189{
1190    using type = __copy_cv_t<_From, _To>;
1191};
1192
1193template <class _From, class _To>
1194struct __copy_cvref<_From&, _To>
1195{
1196    using type = add_lvalue_reference_t<__copy_cv_t<_From, _To>>;
1197};
1198
1199template <class _From, class _To>
1200struct __copy_cvref<_From&&, _To>
1201{
1202    using type = add_rvalue_reference_t<__copy_cv_t<_From, _To>>;
1203};
1204
1205template <class _From, class _To>
1206using __copy_cvref_t = typename __copy_cvref<_From, _To>::type;
1207
1208#endif // _LIBCPP_STD_VER > 11
1209
1210// common_reference
1211#if _LIBCPP_STD_VER > 17
1212// Let COND_RES(X, Y) be:
1213template <class _Xp, class _Yp>
1214using __cond_res =
1215    decltype(false ? declval<_Xp(&)()>()() : declval<_Yp(&)()>()());
1216
1217// Let `XREF(A)` denote a unary alias template `T` such that `T<U>` denotes the same type as `U`
1218// with the addition of `A`'s cv and reference qualifiers, for a non-reference cv-unqualified type
1219// `U`.
1220// [Note: `XREF(A)` is `__xref<A>::template __apply`]
1221template <class _Tp>
1222struct __xref {
1223  template<class _Up>
1224  using __apply = __copy_cvref_t<_Tp, _Up>;
1225};
1226
1227// Given types A and B, let X be remove_reference_t<A>, let Y be remove_reference_t<B>,
1228// and let COMMON-REF(A, B) be:
1229template<class _Ap, class _Bp, class _Xp = remove_reference_t<_Ap>, class _Yp = remove_reference_t<_Bp>>
1230struct __common_ref;
1231
1232template<class _Xp, class _Yp>
1233using __common_ref_t = typename __common_ref<_Xp, _Yp>::__type;
1234
1235template<class _Xp, class _Yp>
1236using __cv_cond_res = __cond_res<__copy_cv_t<_Xp, _Yp>&, __copy_cv_t<_Yp, _Xp>&>;
1237
1238
1239//    If A and B are both lvalue reference types, COMMON-REF(A, B) is
1240//    COND-RES(COPYCV(X, Y)&, COPYCV(Y, X)&) if that type exists and is a reference type.
1241template<class _Ap, class _Bp, class _Xp, class _Yp>
1242requires requires { typename __cv_cond_res<_Xp, _Yp>; } && is_reference_v<__cv_cond_res<_Xp, _Yp>>
1243struct __common_ref<_Ap&, _Bp&, _Xp, _Yp>
1244{
1245    using __type = __cv_cond_res<_Xp, _Yp>;
1246};
1247
1248//    Otherwise, let C be remove_reference_t<COMMON-REF(X&, Y&)>&&. ...
1249template <class _Xp, class _Yp>
1250using __common_ref_C = remove_reference_t<__common_ref_t<_Xp&, _Yp&>>&&;
1251
1252
1253//    .... If A and B are both rvalue reference types, C is well-formed, and
1254//    is_convertible_v<A, C> && is_convertible_v<B, C> is true, then COMMON-REF(A, B) is C.
1255template<class _Ap, class _Bp, class _Xp, class _Yp>
1256requires
1257  requires { typename __common_ref_C<_Xp, _Yp>; } &&
1258  is_convertible_v<_Ap&&, __common_ref_C<_Xp, _Yp>> &&
1259  is_convertible_v<_Bp&&, __common_ref_C<_Xp, _Yp>>
1260struct __common_ref<_Ap&&, _Bp&&, _Xp, _Yp>
1261{
1262    using __type = __common_ref_C<_Xp, _Yp>;
1263};
1264
1265//    Otherwise, let D be COMMON-REF(const X&, Y&). ...
1266template <class _Tp, class _Up>
1267using __common_ref_D = __common_ref_t<const _Tp&, _Up&>;
1268
1269//    ... If A is an rvalue reference and B is an lvalue reference and D is well-formed and
1270//    is_convertible_v<A, D> is true, then COMMON-REF(A, B) is D.
1271template<class _Ap, class _Bp, class _Xp, class _Yp>
1272requires requires { typename __common_ref_D<_Xp, _Yp>; } &&
1273         is_convertible_v<_Ap&&, __common_ref_D<_Xp, _Yp>>
1274struct __common_ref<_Ap&&, _Bp&, _Xp, _Yp>
1275{
1276    using __type = __common_ref_D<_Xp, _Yp>;
1277};
1278
1279//    Otherwise, if A is an lvalue reference and B is an rvalue reference, then
1280//    COMMON-REF(A, B) is COMMON-REF(B, A).
1281template<class _Ap, class _Bp, class _Xp, class _Yp>
1282struct __common_ref<_Ap&, _Bp&&, _Xp, _Yp> : __common_ref<_Bp&&, _Ap&> {};
1283
1284//    Otherwise, COMMON-REF(A, B) is ill-formed.
1285template<class _Ap, class _Bp, class _Xp, class _Yp>
1286struct __common_ref {};
1287
1288// Note C: For the common_reference trait applied to a parameter pack [...]
1289
1290template <class...>
1291struct common_reference;
1292
1293template <class... _Types>
1294using common_reference_t = typename common_reference<_Types...>::type;
1295
1296// bullet 1 - sizeof...(T) == 0
1297template<>
1298struct common_reference<> {};
1299
1300// bullet 2 - sizeof...(T) == 1
1301template <class _Tp>
1302struct common_reference<_Tp>
1303{
1304    using type = _Tp;
1305};
1306
1307// bullet 3 - sizeof...(T) == 2
1308template <class _Tp, class _Up> struct __common_reference_sub_bullet3;
1309template <class _Tp, class _Up> struct __common_reference_sub_bullet2 : __common_reference_sub_bullet3<_Tp, _Up> {};
1310template <class _Tp, class _Up> struct __common_reference_sub_bullet1 : __common_reference_sub_bullet2<_Tp, _Up> {};
1311
1312// sub-bullet 1 - If T1 and T2 are reference types and COMMON-REF(T1, T2) is well-formed, then
1313// the member typedef `type` denotes that type.
1314template <class _Tp, class _Up> struct common_reference<_Tp, _Up> : __common_reference_sub_bullet1<_Tp, _Up> {};
1315
1316template <class _Tp, class _Up>
1317requires is_reference_v<_Tp> && is_reference_v<_Up> && requires { typename __common_ref_t<_Tp, _Up>; }
1318struct __common_reference_sub_bullet1<_Tp, _Up>
1319{
1320    using type = __common_ref_t<_Tp, _Up>;
1321};
1322
1323// sub-bullet 2 - Otherwise, if basic_common_reference<remove_cvref_t<T1>, remove_cvref_t<T2>, XREF(T1), XREF(T2)>::type
1324// is well-formed, then the member typedef `type` denotes that type.
1325template <class, class, template <class> class, template <class> class> struct basic_common_reference {};
1326
1327template <class _Tp, class _Up>
1328using __basic_common_reference_t = typename basic_common_reference<
1329    remove_cvref_t<_Tp>, remove_cvref_t<_Up>,
1330    __xref<_Tp>::template __apply, __xref<_Up>::template __apply>::type;
1331
1332template <class _Tp, class _Up>
1333requires requires { typename __basic_common_reference_t<_Tp, _Up>; }
1334struct __common_reference_sub_bullet2<_Tp, _Up>
1335{
1336    using type = __basic_common_reference_t<_Tp, _Up>;
1337};
1338
1339// sub-bullet 3 - Otherwise, if COND-RES(T1, T2) is well-formed,
1340// then the member typedef `type` denotes that type.
1341template <class _Tp, class _Up>
1342requires requires { typename __cond_res<_Tp, _Up>; }
1343struct __common_reference_sub_bullet3<_Tp, _Up>
1344{
1345    using type = __cond_res<_Tp, _Up>;
1346};
1347
1348
1349// sub-bullet 4 & 5 - Otherwise, if common_type_t<T1, T2> is well-formed,
1350//                    then the member typedef `type` denotes that type.
1351//                  - Otherwise, there shall be no member `type`.
1352template <class _Tp, class _Up> struct __common_reference_sub_bullet3 : common_type<_Tp, _Up> {};
1353
1354// bullet 4 - If there is such a type `C`, the member typedef type shall denote the same type, if
1355//            any, as `common_reference_t<C, Rest...>`.
1356template <class _Tp, class _Up, class _Vp, class... _Rest>
1357requires requires { typename common_reference_t<_Tp, _Up>; }
1358struct common_reference<_Tp, _Up, _Vp, _Rest...>
1359    : common_reference<common_reference_t<_Tp, _Up>, _Vp, _Rest...>
1360{};
1361
1362// bullet 5 - Otherwise, there shall be no member `type`.
1363template <class...> struct common_reference {};
1364
1365#endif // _LIBCPP_STD_VER > 17
1366
1367#ifndef _LIBCPP_CXX03_LANG
1368// First of all, we can't implement this check in C++03 mode because the {}
1369// default initialization syntax isn't valid.
1370// Second, we implement the trait in a funny manner with two defaulted template
1371// arguments to workaround Clang's PR43454.
1372template <class _Tp>
1373void __test_implicit_default_constructible(_Tp);
1374
1375template <class _Tp, class = void, class = typename is_default_constructible<_Tp>::type>
1376struct __is_implicitly_default_constructible
1377    : false_type
1378{ };
1379
1380template <class _Tp>
1381struct __is_implicitly_default_constructible<_Tp, decltype(__test_implicit_default_constructible<_Tp const&>({})), true_type>
1382    : true_type
1383{ };
1384
1385template <class _Tp>
1386struct __is_implicitly_default_constructible<_Tp, decltype(__test_implicit_default_constructible<_Tp const&>({})), false_type>
1387    : false_type
1388{ };
1389#endif // !C++03
1390
1391// result_of
1392
1393#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_TYPE_TRAITS)
1394template <class _Callable> class _LIBCPP_DEPRECATED_IN_CXX17 result_of;
1395
1396#ifndef _LIBCPP_CXX03_LANG
1397
1398template <class _Fp, class ..._Args>
1399class _LIBCPP_TEMPLATE_VIS result_of<_Fp(_Args...)>
1400    : public __invoke_of<_Fp, _Args...>
1401{
1402};
1403
1404#else // C++03
1405
1406template <class _Fn, bool, bool>
1407class __result_of
1408{
1409};
1410
1411template <class _Fn, class ..._Args>
1412class __result_of<_Fn(_Args...), true, false>
1413{
1414public:
1415    typedef decltype(declval<_Fn>()(declval<_Args>()...)) type;
1416};
1417
1418template <class _MP, class _Tp, bool _IsMemberFunctionPtr>
1419struct __result_of_mp;
1420
1421// member function pointer
1422
1423template <class _MP, class _Tp>
1424struct __result_of_mp<_MP, _Tp, true>
1425{
1426    using type = typename __member_pointer_traits<_MP>::_ReturnType;
1427};
1428
1429// member data pointer
1430
1431template <class _MP, class _Tp, bool>
1432struct __result_of_mdp;
1433
1434template <class _Rp, class _Class, class _Tp>
1435struct __result_of_mdp<_Rp _Class::*, _Tp, false>
1436{
1437    using type = typename __apply_cv<decltype(*declval<_Tp>()), _Rp>::type&;
1438};
1439
1440template <class _Rp, class _Class, class _Tp>
1441struct __result_of_mdp<_Rp _Class::*, _Tp, true>
1442{
1443    using type = typename __apply_cv<_Tp, _Rp>::type&;
1444};
1445
1446template <class _Rp, class _Class, class _Tp>
1447struct __result_of_mp<_Rp _Class::*, _Tp, false>
1448    : public __result_of_mdp<_Rp _Class::*, _Tp,
1449            is_base_of<_Class, typename remove_reference<_Tp>::type>::value>
1450{
1451};
1452
1453template <class _Fn, class _Tp>
1454class __result_of<_Fn(_Tp), false, true>  // _Fn must be member pointer
1455    : public __result_of_mp<typename remove_reference<_Fn>::type,
1456                            _Tp,
1457                            is_member_function_pointer<typename remove_reference<_Fn>::type>::value>
1458{
1459};
1460
1461template <class _Fn, class _Tp, class ..._Args>
1462class __result_of<_Fn(_Tp, _Args...), false, true>  // _Fn must be member pointer
1463    : public __result_of_mp<typename remove_reference<_Fn>::type,
1464                            _Tp,
1465                            is_member_function_pointer<typename remove_reference<_Fn>::type>::value>
1466{
1467};
1468
1469template <class _Fn, class ..._Args>
1470class _LIBCPP_TEMPLATE_VIS result_of<_Fn(_Args...)>
1471    : public __result_of<_Fn(_Args...),
1472                         is_class<typename remove_reference<_Fn>::type>::value ||
1473                         is_function<typename remove_pointer<typename remove_reference<_Fn>::type>::type>::value,
1474                         is_member_pointer<typename remove_reference<_Fn>::type>::value
1475                        >
1476{
1477};
1478
1479#endif // C++03
1480
1481#if _LIBCPP_STD_VER > 11
1482template <class _Tp> using result_of_t _LIBCPP_DEPRECATED_IN_CXX17 = typename result_of<_Tp>::type;
1483#endif // _LIBCPP_STD_VER > 11
1484#endif // _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_TYPE_TRAITS)
1485
1486// __swappable
1487
1488template <class _Tp> struct __is_swappable;
1489template <class _Tp> struct __is_nothrow_swappable;
1490
1491
1492#ifndef _LIBCPP_CXX03_LANG
1493template <class _Tp>
1494using __swap_result_t = typename enable_if<is_move_constructible<_Tp>::value && is_move_assignable<_Tp>::value>::type;
1495#else
1496template <class>
1497using __swap_result_t = void;
1498#endif
1499
1500template <class _Tp>
1501inline _LIBCPP_INLINE_VISIBILITY
1502_LIBCPP_CONSTEXPR_AFTER_CXX17 __swap_result_t<_Tp>
1503swap(_Tp& __x, _Tp& __y) _NOEXCEPT_(is_nothrow_move_constructible<_Tp>::value &&
1504                                    is_nothrow_move_assignable<_Tp>::value);
1505
1506template<class _Tp, size_t _Np>
1507inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1508typename enable_if<
1509    __is_swappable<_Tp>::value
1510>::type
1511swap(_Tp (&__a)[_Np], _Tp (&__b)[_Np]) _NOEXCEPT_(__is_nothrow_swappable<_Tp>::value);
1512
1513namespace __detail
1514{
1515// ALL generic swap overloads MUST already have a declaration available at this point.
1516
1517template <class _Tp, class _Up = _Tp,
1518          bool _NotVoid = !is_void<_Tp>::value && !is_void<_Up>::value>
1519struct __swappable_with
1520{
1521    template <class _LHS, class _RHS>
1522    static decltype(swap(declval<_LHS>(), declval<_RHS>()))
1523    __test_swap(int);
1524    template <class, class>
1525    static __nat __test_swap(long);
1526
1527    // Extra parens are needed for the C++03 definition of decltype.
1528    typedef decltype((__test_swap<_Tp, _Up>(0))) __swap1;
1529    typedef decltype((__test_swap<_Up, _Tp>(0))) __swap2;
1530
1531    static const bool value = _IsNotSame<__swap1, __nat>::value
1532                           && _IsNotSame<__swap2, __nat>::value;
1533};
1534
1535template <class _Tp, class _Up>
1536struct __swappable_with<_Tp, _Up,  false> : false_type {};
1537
1538template <class _Tp, class _Up = _Tp, bool _Swappable = __swappable_with<_Tp, _Up>::value>
1539struct __nothrow_swappable_with {
1540  static const bool value =
1541#ifndef _LIBCPP_HAS_NO_NOEXCEPT
1542      noexcept(swap(declval<_Tp>(), declval<_Up>()))
1543  &&  noexcept(swap(declval<_Up>(), declval<_Tp>()));
1544#else
1545      false;
1546#endif
1547};
1548
1549template <class _Tp, class _Up>
1550struct __nothrow_swappable_with<_Tp, _Up, false> : false_type {};
1551
1552} // namespace __detail
1553
1554template <class _Tp>
1555struct __is_swappable
1556    : public integral_constant<bool, __detail::__swappable_with<_Tp&>::value>
1557{
1558};
1559
1560template <class _Tp>
1561struct __is_nothrow_swappable
1562    : public integral_constant<bool, __detail::__nothrow_swappable_with<_Tp&>::value>
1563{
1564};
1565
1566#if _LIBCPP_STD_VER > 14
1567
1568template <class _Tp, class _Up>
1569struct _LIBCPP_TEMPLATE_VIS is_swappable_with
1570    : public integral_constant<bool, __detail::__swappable_with<_Tp, _Up>::value>
1571{
1572};
1573
1574template <class _Tp>
1575struct _LIBCPP_TEMPLATE_VIS is_swappable
1576    : public conditional<
1577        __is_referenceable<_Tp>::value,
1578        is_swappable_with<
1579            typename add_lvalue_reference<_Tp>::type,
1580            typename add_lvalue_reference<_Tp>::type>,
1581        false_type
1582    >::type
1583{
1584};
1585
1586template <class _Tp, class _Up>
1587struct _LIBCPP_TEMPLATE_VIS is_nothrow_swappable_with
1588    : public integral_constant<bool, __detail::__nothrow_swappable_with<_Tp, _Up>::value>
1589{
1590};
1591
1592template <class _Tp>
1593struct _LIBCPP_TEMPLATE_VIS is_nothrow_swappable
1594    : public conditional<
1595        __is_referenceable<_Tp>::value,
1596        is_nothrow_swappable_with<
1597            typename add_lvalue_reference<_Tp>::type,
1598            typename add_lvalue_reference<_Tp>::type>,
1599        false_type
1600    >::type
1601{
1602};
1603
1604template <class _Tp, class _Up>
1605inline constexpr bool is_swappable_with_v = is_swappable_with<_Tp, _Up>::value;
1606
1607template <class _Tp>
1608inline constexpr bool is_swappable_v = is_swappable<_Tp>::value;
1609
1610template <class _Tp, class _Up>
1611inline constexpr bool is_nothrow_swappable_with_v = is_nothrow_swappable_with<_Tp, _Up>::value;
1612
1613template <class _Tp>
1614inline constexpr bool is_nothrow_swappable_v = is_nothrow_swappable<_Tp>::value;
1615
1616#endif // _LIBCPP_STD_VER > 14
1617
1618template <class _Tp, bool = is_enum<_Tp>::value>
1619struct __sfinae_underlying_type
1620{
1621    typedef typename underlying_type<_Tp>::type type;
1622    typedef decltype(((type)1) + 0) __promoted_type;
1623};
1624
1625template <class _Tp>
1626struct __sfinae_underlying_type<_Tp, false> {};
1627
1628inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
1629int __convert_to_integral(int __val) { return __val; }
1630
1631inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
1632unsigned __convert_to_integral(unsigned __val) { return __val; }
1633
1634inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
1635long __convert_to_integral(long __val) { return __val; }
1636
1637inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
1638unsigned long __convert_to_integral(unsigned long __val) { return __val; }
1639
1640inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
1641long long __convert_to_integral(long long __val) { return __val; }
1642
1643inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
1644unsigned long long __convert_to_integral(unsigned long long __val) {return __val; }
1645
1646template<typename _Fp>
1647inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
1648typename enable_if<is_floating_point<_Fp>::value, long long>::type
1649 __convert_to_integral(_Fp __val) { return __val; }
1650
1651#ifndef _LIBCPP_HAS_NO_INT128
1652inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
1653__int128_t __convert_to_integral(__int128_t __val) { return __val; }
1654
1655inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
1656__uint128_t __convert_to_integral(__uint128_t __val) { return __val; }
1657#endif
1658
1659template <class _Tp>
1660inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
1661typename __sfinae_underlying_type<_Tp>::__promoted_type
1662__convert_to_integral(_Tp __val) { return __val; }
1663
1664// These traits are used in __tree and __hash_table
1665struct __extract_key_fail_tag {};
1666struct __extract_key_self_tag {};
1667struct __extract_key_first_tag {};
1668
1669template <class _ValTy, class _Key,
1670          class _RawValTy = typename __unconstref<_ValTy>::type>
1671struct __can_extract_key
1672    : conditional<_IsSame<_RawValTy, _Key>::value, __extract_key_self_tag,
1673                  __extract_key_fail_tag>::type {};
1674
1675template <class _Pair, class _Key, class _First, class _Second>
1676struct __can_extract_key<_Pair, _Key, pair<_First, _Second> >
1677    : conditional<_IsSame<typename remove_const<_First>::type, _Key>::value,
1678                  __extract_key_first_tag, __extract_key_fail_tag>::type {};
1679
1680// __can_extract_map_key uses true_type/false_type instead of the tags.
1681// It returns true if _Key != _ContainerValueTy (the container is a map not a set)
1682// and _ValTy == _Key.
1683template <class _ValTy, class _Key, class _ContainerValueTy,
1684          class _RawValTy = typename __unconstref<_ValTy>::type>
1685struct __can_extract_map_key
1686    : integral_constant<bool, _IsSame<_RawValTy, _Key>::value> {};
1687
1688// This specialization returns __extract_key_fail_tag for non-map containers
1689// because _Key == _ContainerValueTy
1690template <class _ValTy, class _Key, class _RawValTy>
1691struct __can_extract_map_key<_ValTy, _Key, _Key, _RawValTy>
1692    : false_type {};
1693
1694template <class _CharT>
1695using _IsCharLikeType = _And<is_standard_layout<_CharT>, is_trivial<_CharT> >;
1696
1697template<class _Tp>
1698using __make_const_lvalue_ref = const typename remove_reference<_Tp>::type&;
1699
1700#if _LIBCPP_STD_VER > 17
1701template<bool _Const, class _Tp>
1702using __maybe_const = conditional_t<_Const, const _Tp, _Tp>;
1703#endif // _LIBCPP_STD_VER > 17
1704
1705_LIBCPP_END_NAMESPACE_STD
1706
1707#endif // _LIBCPP_TYPE_TRAITS
1708