92 lines · cpp
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-exception6//7//===----------------------------------------------------------------------===//8 9// UNSUPPORTED: c++03, c++11, c++14, c++1710 11// constexpr iterator& operator--() requires bidirectional_range<Base>;12// constexpr iterator operator--(int) requires bidirectional_range<Base>;13 14#include <array>15#include <cassert>16#include <ranges>17#include <tuple>18 19#include "test_iterators.h"20 21template <class Iter>22concept CanPreDecrement = requires(Iter it) { --it; };23 24template <class Iter>25concept CanPostDecrement = requires(Iter it) { it--; };26 27template <class Iter, class Sent = sentinel_wrapper<Iter>>28constexpr void testOne() {29 using Range = std::ranges::subrange<Iter, Sent>;30 std::tuple<int> ts[] = {{1}, {2}, {3}};31 auto ev = Range{Iter{&ts[0]}, Sent{Iter{&ts[0] + 3}}} | std::views::elements<0>;32 33 using ElementIter = std::ranges::iterator_t<decltype(ev)>;34 35 if constexpr (!std::bidirectional_iterator<Iter>) {36 auto it = ev.begin();37 static_assert(!CanPreDecrement<decltype(it)>);38 static_assert(!CanPostDecrement<decltype(it)>);39 } else {40 // --i41 {42 auto it = ev.begin();43 static_assert(CanPreDecrement<decltype(it)>);44 45 ++it;46 assert(base(it.base()) == &ts[1]);47 48 decltype(auto) result = --it;49 50 static_assert(std::is_same_v<decltype(result), ElementIter&>);51 assert(&result == &it);52 53 assert(base(it.base()) == &ts[0]);54 }55 56 // i--57 {58 auto it = ev.begin();59 static_assert(CanPostDecrement<decltype(it)>);60 61 ++it;62 assert(base(it.base()) == &ts[1]);63 64 decltype(auto) result = it--;65 66 static_assert(std::is_same_v<decltype(result), ElementIter>);67 68 assert(base(it.base()) == &ts[0]);69 assert(base(result.base()) == &ts[1]);70 }71 }72}73 74constexpr bool test() {75 using Ptr = std::tuple<int>*;76 testOne<cpp20_input_iterator<Ptr>>();77 testOne<forward_iterator<Ptr>>();78 testOne<bidirectional_iterator<Ptr>>();79 testOne<random_access_iterator<Ptr>>();80 testOne<contiguous_iterator<Ptr>>();81 testOne<Ptr>();82 83 return true;84}85 86int main(int, char**) {87 test();88 static_assert(test());89 90 return 0;91}92