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 
11 // template<class F, class... Args>
12 // concept predicate;
13 
14 #include <concepts>
15 #include <type_traits>
16 
17 static_assert(std::predicate<bool()>);
18 static_assert(std::predicate<bool (*)()>);
19 static_assert(std::predicate<bool (&)()>);
20 
21 static_assert(!std::predicate<void()>);
22 static_assert(!std::predicate<void (*)()>);
23 static_assert(!std::predicate<void (&)()>);
24 
25 struct S {};
26 
27 static_assert(!std::predicate<S(int), int>);
28 static_assert(!std::predicate<S(double), double>);
29 static_assert(std::predicate<int S::*, S*>);
30 static_assert(std::predicate<int (S::*)(), S*>);
31 static_assert(std::predicate<int (S::*)(), S&>);
32 static_assert(!std::predicate<void (S::*)(), S*>);
33 static_assert(!std::predicate<void (S::*)(), S&>);
34 
35 static_assert(!std::predicate<bool(S)>);
36 static_assert(!std::predicate<bool(S&), S>);
37 static_assert(!std::predicate<bool(S&), S const&>);
38 static_assert(std::predicate<bool(S&), S&>);
39 
40 struct Predicate {
41   bool operator()(int, double, char);
42 };
43 static_assert(std::predicate<Predicate, int, double, char>);
44 static_assert(std::predicate<Predicate&, int, double, char>);
45 static_assert(!std::predicate<const Predicate, int, double, char>);
46 static_assert(!std::predicate<const Predicate&, int, double, char>);
47 
48 constexpr bool check_lambda(auto) { return false; }
49 
50 constexpr bool check_lambda(std::predicate auto) { return true; }
51 
52 static_assert(check_lambda([] { return std::true_type(); }));
53 static_assert(check_lambda([]() -> int* { return nullptr; }));
54 
55 struct boolean {
56   operator bool() const noexcept;
57 };
58 static_assert(check_lambda([] { return boolean(); }));
59 
60 struct explicit_bool {
61   explicit operator bool() const noexcept;
62 };
63 static_assert(!check_lambda([] { return explicit_bool(); }));
64