1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
10
11// <functional>
12
13// template<class F, class... Args>
14// constexpr unspecified bind_back(F&& f, Args&&... args);
15
16#include <functional>
17
18#include <cassert>
19#include <concepts>
20#include <tuple>
21#include <utility>
22
23#include "callable_types.h"
24#include "types.h"
25
26constexpr void test_basic_bindings() {
27 { // Bind arguments, call without arguments
28 {
29 auto f = std::bind_back(MakeTuple{});
30 assert(f() == std::make_tuple());
31 }
32 {
33 auto f = std::bind_back(MakeTuple{}, Elem<1>{});
34 assert(f() == std::make_tuple(Elem<1>{}));
35 }
36 {
37 auto f = std::bind_back(MakeTuple{}, Elem<1>{}, Elem<2>{});
38 assert(f() == std::make_tuple(Elem<1>{}, Elem<2>{}));
39 }
40 {
41 auto f = std::bind_back(MakeTuple{}, Elem<1>{}, Elem<2>{}, Elem<3>{});
42 assert(f() == std::make_tuple(Elem<1>{}, Elem<2>{}, Elem<3>{}));
43 }
44 }
45
46 { // Bind no arguments, call with arguments
47 {
48 auto f = std::bind_back(MakeTuple{});
49 assert(f(Elem<1>{}) == std::make_tuple(Elem<1>{}));
50 }
51 {
52 auto f = std::bind_back(MakeTuple{});
53 assert(f(Elem<1>{}, Elem<2>{}) == std::make_tuple(Elem<1>{}, Elem<2>{}));
54 }
55 {
56 auto f = std::bind_back(MakeTuple{});
57 assert(f(Elem<1>{}, Elem<2>{}, Elem<3>{}) == std::make_tuple(Elem<1>{}, Elem<2>{}, Elem<3>{}));
58 }
59 }
60
61 { // Bind arguments, call with arguments
62 {
63 auto f = std::bind_back(MakeTuple{}, Elem<1>{});
64 assert(f(Elem<10>{}) == std::make_tuple(Elem<10>{}, Elem<1>{}));
65 }
66 {
67 auto f = std::bind_back(MakeTuple{}, Elem<1>{}, Elem<2>{});
68 assert(f(Elem<10>{}) == std::make_tuple(Elem<10>{}, Elem<1>{}, Elem<2>{}));
69 }
70 {
71 auto f = std::bind_back(MakeTuple{}, Elem<1>{}, Elem<2>{}, Elem<3>{});
72 assert(f(Elem<10>{}) == std::make_tuple(Elem<10>{}, Elem<1>{}, Elem<2>{}, Elem<3>{}));
73 }
74
75 {
76 auto f = std::bind_back(MakeTuple{}, Elem<1>{});
77 assert(f(Elem<10>{}, Elem<11>{}) == std::make_tuple(Elem<10>{}, Elem<11>{}, Elem<1>{}));
78 }
79 {
80 auto f = std::bind_back(MakeTuple{}, Elem<1>{}, Elem<2>{});
81 assert(f(Elem<10>{}, Elem<11>{}) == std::make_tuple(Elem<10>{}, Elem<11>{}, Elem<1>{}, Elem<2>{}));
82 }
83 {
84 auto f = std::bind_back(MakeTuple{}, Elem<1>{}, Elem<2>{}, Elem<3>{});
85 assert(f(Elem<10>{}, Elem<11>{}) == std::make_tuple(Elem<10>{}, Elem<11>{}, Elem<1>{}, Elem<2>{}, Elem<3>{}));
86 }
87 {
88 auto f = std::bind_back(MakeTuple{}, Elem<1>{}, Elem<2>{}, Elem<3>{});
89 assert(f(Elem<10>{}, Elem<11>{}, Elem<12>{}) ==
90 std::make_tuple(Elem<10>{}, Elem<11>{}, Elem<12>{}, Elem<1>{}, Elem<2>{}, Elem<3>{}));
91 }
92 }
93
94 { // Basic tests with fundamental types
95 int n = 2;
96 int m = 1;
97 int sum = 0;
98 auto add = [](int x, int y) { return x + y; };
99 auto add_n = [](int a, int b, int c, int d, int e, int f) { return a + b + c + d + e + f; };
100 auto add_ref = [&](int x, int y) -> int& { return sum = x + y; };
101 auto add_rref = [&](int x, int y) -> int&& { return std::move(sum = x + y); };
102
103 auto a = std::bind_back(add, m, n);
104 assert(a() == 3);
105
106 auto b = std::bind_back(add_n, m, n, m, m, m, m);
107 assert(b() == 7);
108
109 auto c = std::bind_back(add_n, n, m);
110 assert(c(1, 1, 1, 1) == 7);
111
112 auto d = std::bind_back(add_ref, n, m);
113 std::same_as<int&> decltype(auto) dresult(d());
114 assert(dresult == 3);
115
116 auto e = std::bind_back(add_rref, n, m);
117 std::same_as<int&&> decltype(auto) eresult(e());
118 assert(eresult == 3);
119
120 auto f = std::bind_back(add, n);
121 assert(f(3) == 5);
122
123 auto g = std::bind_back(add, n, 1);
124 assert(g() == 3);
125
126 auto h = std::bind_back(add_n, 1, 1, 1);
127 assert(h(2, 2, 2) == 9);
128
129 auto i = std::bind_back(add_ref, n);
130 std::same_as<int&> decltype(auto) iresult(i(5));
131 assert(iresult == 7);
132
133 auto j = std::bind_back(add_rref, m);
134 std::same_as<int&&> decltype(auto) jresult(j(4));
135 assert(jresult == 5);
136 }
137}
138
139constexpr void test_edge_cases() {
140 { // Make sure we don't treat std::reference_wrapper specially.
141 auto sub = [](std::reference_wrapper<int> a, std::reference_wrapper<int> b) { return a.get() - b.get(); };
142
143 int i = 1;
144 int j = 2;
145 auto f = std::bind_back(sub, std::ref(i));
146 assert(f(std::ref(j)) == 1);
147 }
148
149 { // Make sure we can call a function that's a pointer to a member function.
150 struct MemberFunction {
151 constexpr int foo(int x, int y) { return x * y; }
152 };
153
154 MemberFunction value;
155 auto fn = std::bind_back(&MemberFunction::foo, 2, 3);
156 assert(fn(value) == 6);
157 }
158
159 { // Make sure we can call a function that's a pointer to a member object.
160 struct MemberObject {
161 int obj;
162 };
163
164 MemberObject value{.obj = 3};
165 auto fn = std::bind_back(&MemberObject::obj);
166 assert(fn(value) == 3);
167 }
168}
169
170constexpr void test_passing_arguments() {
171 { // Make sure that we copy the bound arguments into the unspecified-type.
172 auto add = [](int x, int y) { return x + y; };
173 int n = 2;
174 auto f = std::bind_back(add, n, 1);
175 n = 100;
176 assert(f() == 3);
177 }
178
179 { // Make sure we pass the bound arguments to the function object
180 // with the right value category.
181 {
182 auto was_copied = [](CopyMoveInfo info) { return info.copy_kind == CopyMoveInfo::copy; };
183 CopyMoveInfo info;
184 auto f = std::bind_back(was_copied, info);
185 assert(f());
186 }
187
188 {
189 auto was_moved = [](CopyMoveInfo info) { return info.copy_kind == CopyMoveInfo::move; };
190 CopyMoveInfo info;
191 auto f = std::bind_back(was_moved, info);
192 assert(std::move(f)());
193 }
194 }
195}
196
197constexpr void test_function_objects() {
198 { // Make sure we call the correctly cv-ref qualified operator()
199 // based on the value category of the bind_back unspecified-type.
200 struct X {
201 constexpr int operator()() & { return 1; }
202 constexpr int operator()() const& { return 2; }
203 constexpr int operator()() && { return 3; }
204 constexpr int operator()() const&& { return 4; }
205 };
206
207 auto f = std::bind_back(X{});
208 using F = decltype(f);
209 assert(static_cast<F&>(f)() == 1);
210 assert(static_cast<const F&>(f)() == 2);
211 assert(static_cast<F&&>(f)() == 3);
212 assert(static_cast<const F&&>(f)() == 4);
213 }
214
215 // Make sure the `bind_back` unspecified-type does not model invocable
216 // when the call would select a differently-qualified operator().
217 //
218 // For example, if the call to `operator()() &` is ill-formed, the call to the unspecified-type
219 // should be ill-formed and not fall back to the `operator()() const&` overload.
220 { // Make sure we delete the & overload when the underlying call isn't valid.
221 {
222 struct X {
223 void operator()() & = delete;
224 void operator()() const&;
225 void operator()() &&;
226 void operator()() const&&;
227 };
228
229 using F = decltype(std::bind_back(X{}));
230 static_assert(!std::invocable<F&>);
231 static_assert(std::invocable<const F&>);
232 static_assert(std::invocable<F>);
233 static_assert(std::invocable<const F>);
234 }
235
236 // There's no way to make sure we delete the const& overload when the underlying call isn't valid,
237 // so we can't check this one.
238
239 { // Make sure we delete the && overload when the underlying call isn't valid.
240 struct X {
241 void operator()() &;
242 void operator()() const&;
243 void operator()() && = delete;
244 void operator()() const&&;
245 };
246
247 using F = decltype(std::bind_back(X{}));
248 static_assert(std::invocable<F&>);
249 static_assert(std::invocable<const F&>);
250 static_assert(!std::invocable<F>);
251 static_assert(std::invocable<const F>);
252 }
253
254 { // Make sure we delete the const&& overload when the underlying call isn't valid.
255 struct X {
256 void operator()() &;
257 void operator()() const&;
258 void operator()() &&;
259 void operator()() const&& = delete;
260 };
261
262 using F = decltype(std::bind_back(X{}));
263 static_assert(std::invocable<F&>);
264 static_assert(std::invocable<const F&>);
265 static_assert(std::invocable<F>);
266 static_assert(!std::invocable<const F>);
267 }
268 }
269
270 { // Extra value category tests
271 struct X {};
272
273 {
274 struct Y {
275 void operator()(X&&) const&;
276 void operator()(X&&) && = delete;
277 };
278
279 using F = decltype(std::bind_back(Y{}));
280 static_assert(std::invocable<F&, X>);
281 static_assert(!std::invocable<F, X>);
282 }
283
284 {
285 struct Y {
286 void operator()(const X&) const;
287 void operator()(X&&) const = delete;
288 };
289
290 using F = decltype(std::bind_back(Y{}, X{}));
291 static_assert(std::invocable<F&>);
292 static_assert(!std::invocable<F>);
293 }
294 }
295}
296
297constexpr void test_return_type() {
298 { // Test properties of the constructor of the unspecified-type returned by bind_back.
299 { // Test move constructor when function is move only.
300 MoveOnlyCallable<bool> value(true);
301 auto f = std::bind_back(std::move(value), 1);
302 assert(f());
303 assert(f(1, 2, 3));
304
305 auto f1 = std::move(f);
306 assert(!f());
307 assert(f1());
308 assert(f1(1, 2, 3));
309
310 using F = decltype(f);
311 static_assert(std::is_move_constructible<F>::value);
312 static_assert(!std::is_copy_constructible<F>::value);
313 static_assert(!std::is_move_assignable<F>::value);
314 static_assert(!std::is_copy_assignable<F>::value);
315 }
316
317 { // Test move constructor when function is copyable but not assignable.
318 CopyCallable<bool> value(true);
319 auto f = std::bind_back(value, 1);
320 assert(f());
321 assert(f(1, 2, 3));
322
323 auto f1 = std::move(f);
324 assert(!f());
325 assert(f1());
326 assert(f1(1, 2, 3));
327
328 auto f2 = std::bind_back(std::move(value), 1);
329 assert(f1());
330 assert(f2());
331 assert(f2(1, 2, 3));
332
333 using F = decltype(f);
334 static_assert(std::is_move_constructible<F>::value);
335 static_assert(std::is_copy_constructible<F>::value);
336 static_assert(!std::is_move_assignable<F>::value);
337 static_assert(!std::is_copy_assignable<F>::value);
338 }
339
340 { // Test constructors when function is copy assignable.
341 using F = decltype(std::bind_back(std::declval<CopyAssignableWrapper&>(), 1));
342 static_assert(std::is_move_constructible<F>::value);
343 static_assert(std::is_copy_constructible<F>::value);
344 static_assert(std::is_move_assignable<F>::value);
345 static_assert(std::is_copy_assignable<F>::value);
346 }
347
348 { // Test constructors when function is move assignable only.
349 using F = decltype(std::bind_back(std::declval<MoveAssignableWrapper>(), 1));
350 static_assert(std::is_move_constructible<F>::value);
351 static_assert(!std::is_copy_constructible<F>::value);
352 static_assert(std::is_move_assignable<F>::value);
353 static_assert(!std::is_copy_assignable<F>::value);
354 }
355 }
356
357 { // Make sure bind_back's unspecified type's operator() is SFINAE-friendly.
358 using F = decltype(std::bind_back(std::declval<int (*)(int, int)>(), 1));
359 static_assert(!std::is_invocable<F>::value);
360 static_assert(std::is_invocable<F, int>::value);
361 static_assert(!std::is_invocable<F, void*>::value);
362 static_assert(!std::is_invocable<F, int, int>::value);
363 }
364}
365
366constexpr bool test() {
367 test_basic_bindings();
368 test_edge_cases();
369 test_passing_arguments();
370 test_function_objects();
371 test_return_type();
372
373 return true;
374}
375
376int main(int, char**) {
377 test();
378 static_assert(test());
379
380 return 0;
381}
382

source code of libcxx/test/std/utilities/function.objects/func.bind.partial/bind_back.pass.cpp