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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03, c++11, c++14, c++17
// constexpr iterator& operator--() requires bidirectional_range<Base>;
// constexpr iterator operator--(int) requires bidirectional_range<Base>;
#include <array>
#include <cassert>
#include <ranges>
#include <tuple>
#include "test_iterators.h"
template <class Iter>
concept CanPreDecrement = requires(Iter it) { --it; };
template <class Iter>
concept CanPostDecrement = requires(Iter it) { it--; };
template <class Iter, class Sent = sentinel_wrapper<Iter>>
constexpr void testOne() {
using Range = std::ranges::subrange<Iter, Sent>;
std::tuple<int> ts[] = {{1}, {2}, {3}};
auto ev = Range{Iter{&ts[0]}, Sent{Iter{&ts[0] + 3}}} | std::views::elements<0>;
using ElementIter = std::ranges::iterator_t<decltype(ev)>;
if constexpr (!std::bidirectional_iterator<Iter>) {
auto it = ev.begin();
static_assert(!CanPreDecrement<decltype(it)>);
static_assert(!CanPostDecrement<decltype(it)>);
} else {
// --i
{
auto it = ev.begin();
static_assert(CanPreDecrement<decltype(it)>);
++it;
assert(base(it.base()) == &ts[1]);
decltype(auto) result = --it;
static_assert(std::is_same_v<decltype(result), ElementIter&>);
assert(&result == &it);
assert(base(it.base()) == &ts[0]);
}
// i--
{
auto it = ev.begin();
static_assert(CanPostDecrement<decltype(it)>);
++it;
assert(base(it.base()) == &ts[1]);
decltype(auto) result = it--;
static_assert(std::is_same_v<decltype(result), ElementIter>);
assert(base(it.base()) == &ts[0]);
assert(base(result.base()) == &ts[1]);
}
}
}
constexpr bool test() {
using Ptr = std::tuple<int>*;
testOne<cpp20_input_iterator<Ptr>>();
testOne<forward_iterator<Ptr>>();
testOne<bidirectional_iterator<Ptr>>();
testOne<random_access_iterator<Ptr>>();
testOne<contiguous_iterator<Ptr>>();
testOne<Ptr>();
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}
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