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 // ranges::prev
12 // Make sure we're SFINAE-friendly when the template argument constraints are not met.
13 
14 #include <iterator>
15 
16 #include <cstddef>
17 #include <utility>
18 #include "test_iterators.h"
19 
20 template <class ...Args>
21 concept has_ranges_prev = requires (Args&& ...args) {
22   { std::ranges::prev(std::forward<Args>(args)...) };
23 };
24 
25 using It = forward_iterator<int*>;
26 static_assert(!has_ranges_prev<It>);
27 static_assert(!has_ranges_prev<It, std::ptrdiff_t>);
28 static_assert(!has_ranges_prev<It, std::ptrdiff_t, It>);
29 
30 // Test the test
31 using It2 = bidirectional_iterator<int*>;
32 static_assert(has_ranges_prev<It2>);
33 static_assert(has_ranges_prev<It2, std::ptrdiff_t>);
34 static_assert(has_ranges_prev<It2, std::ptrdiff_t, It2>);
35