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
10 // UNSUPPORTED: libcpp-no-concepts
11 
12 // template<class F, class... Args>
13 // concept predicate;
14 
15 #include <concepts>
16 #include <type_traits>
17 
18 static_assert(std::predicate<bool()>);
19 static_assert(std::predicate<bool (*)()>);
20 static_assert(std::predicate<bool (&)()>);
21 
22 static_assert(!std::predicate<void()>);
23 static_assert(!std::predicate<void (*)()>);
24 static_assert(!std::predicate<void (&)()>);
25 
26 struct S {};
27 
28 static_assert(!std::predicate<S(int), int>);
29 static_assert(!std::predicate<S(double), double>);
30 static_assert(std::predicate<int S::*, S*>);
31 static_assert(std::predicate<int (S::*)(), S*>);
32 static_assert(std::predicate<int (S::*)(), S&>);
33 static_assert(!std::predicate<void (S::*)(), S*>);
34 static_assert(!std::predicate<void (S::*)(), S&>);
35 
36 static_assert(!std::predicate<bool(S)>);
37 static_assert(!std::predicate<bool(S&), S>);
38 static_assert(!std::predicate<bool(S&), S const&>);
39 static_assert(std::predicate<bool(S&), S&>);
40 
41 struct Predicate {
42   bool operator()(int, double, char);
43 };
44 static_assert(std::predicate<Predicate, int, double, char>);
45 static_assert(std::predicate<Predicate&, int, double, char>);
46 static_assert(!std::predicate<const Predicate, int, double, char>);
47 static_assert(!std::predicate<const Predicate&, int, double, char>);
48 
49 constexpr bool check_lambda(auto) { return false; }
50 
51 constexpr bool check_lambda(std::predicate auto) { return true; }
52 
53 static_assert(check_lambda([] { return std::true_type(); }));
54 static_assert(check_lambda([]() -> int* { return nullptr; }));
55 
56 struct boolean {
57   operator bool() const noexcept;
58 };
59 static_assert(check_lambda([] { return boolean(); }));
60 
61 struct explicit_bool {
62   explicit operator bool() const noexcept;
63 };
64 static_assert(!check_lambda([] { return explicit_bool(); }));
65