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 // UNSUPPORTED: gcc-10
12 
13 // ranges::prev
14 // Make sure we're SFINAE-friendly when the template argument constraints are not met.
15 
16 #include <iterator>
17 
18 #include <cstddef>
19 #include <utility>
20 #include "test_iterators.h"
21 
22 template <class ...Args>
23 concept has_ranges_prev = requires (Args ...args) {
24   { std::ranges::prev(std::forward<Args>(args)...) };
25 };
26 
27 using It = forward_iterator<int*>;
28 static_assert(!has_ranges_prev<It>);
29 static_assert(!has_ranges_prev<It, std::ptrdiff_t>);
30 static_assert(!has_ranges_prev<It, std::ptrdiff_t, It>);
31 
32 // Test the test
33 static_assert(has_ranges_prev<int*, std::ptrdiff_t, int*>);
34