1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
|
//===----------------------------------------------------------------------===//
//
// 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 decltype(auto) operator*() const;
#include <array>
#include <cassert>
#include <ranges>
#include <tuple>
#include <utility>
template <std::size_t N, class T, std::size_t Size>
constexpr void testReference(T (&ts)[Size]) {
auto ev = ts | std::views::elements<N>;
auto it = ev.begin();
decltype(auto) result = *it;
using ExpectedType = decltype(std::get<N>(ts[0]));
static_assert(std::is_same_v<decltype(result), ExpectedType>);
if constexpr (std::is_reference_v<ExpectedType>) {
// tuple/array/pair
assert(&result == &std::get<N>(ts[0]));
} else {
// subrange
assert(result == std::get<N>(ts[0]));
}
}
// LWG 3502 elements_view should not be allowed to return dangling references
template <std::size_t N, class T>
constexpr void testValue(T t) {
auto ev = std::views::iota(0, 1) | std::views::transform([&t](int) { return t; }) | std::views::elements<N>;
auto it = ev.begin();
decltype(auto) result = *it;
using ExpectedType = std::remove_cvref_t<decltype(std::get<N>(t))>;
static_assert(std::is_same_v<decltype(result), ExpectedType>);
assert(result == std::get<N>(t));
}
constexpr bool test() {
// test tuple
{
std::tuple<int, short, long> ts[] = {{1, 2, 3}, {4, 5, 6}};
testReference<0>(ts);
testReference<1>(ts);
testReference<2>(ts);
testValue<0>(ts[0]);
testValue<1>(ts[0]);
testValue<2>(ts[0]);
}
// test pair
{
std::pair<int, short> ps[] = {{1, 2}, {4, 5}};
testReference<0>(ps);
testReference<1>(ps);
testValue<0>(ps[0]);
testValue<1>(ps[0]);
}
// test array
{
std::array<int, 3> arrs[] = {{1, 2, 3}, {3, 4, 5}};
testReference<0>(arrs);
testReference<1>(arrs);
testReference<2>(arrs);
testValue<0>(arrs[0]);
testValue<1>(arrs[0]);
testValue<2>(arrs[0]);
}
// test subrange
{
int i = 5;
std::ranges::subrange<int*> srs[] = {{&i, &i}, {&i, &i}};
testReference<0>(srs);
testReference<1>(srs);
testValue<0>(srs[0]);
testValue<1>(srs[0]);
}
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}
|
