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
101
102
103
104
105
|
//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
// <tuple>
// template <class... Types> class tuple;
// UNSUPPORTED: c++98, c++03
#include <tuple>
#include <utility>
#include <cassert>
#include "test_macros.h"
template <class ConstructFrom>
struct ConstructibleFromT {
ConstructibleFromT() = default;
ConstructibleFromT(ConstructFrom v) : value(v) {}
ConstructFrom value;
};
template <class AssertOn>
struct CtorAssertsT {
bool defaulted;
CtorAssertsT() : defaulted(true) {}
template <class T>
constexpr CtorAssertsT(T) : defaulted(false) {
static_assert(!std::is_same<T, AssertOn>::value, "");
}
};
template <class AllowT, class AssertT>
struct AllowAssertT {
AllowAssertT() = default;
AllowAssertT(AllowT) {}
template <class U>
constexpr AllowAssertT(U) {
static_assert(!std::is_same<U, AssertT>::value, "");
}
};
// Construct a tuple<T1, T2> from pair<int, int> where T1 and T2
// are not constructible from ints but T1 is constructible from std::pair.
// This considers the following constructors:
// (1) tuple(TupleLike) -> checks is_constructible<Tn, int>
// (2) tuple(UTypes...) -> checks is_constructible<T1, pair<int, int>>
// and is_default_constructible<T2>
// The point of this test is to ensure that the consideration of (1)
// short circuits before evaluating is_constructible<T2, int>, which
// will cause a static assertion.
void test_tuple_like_lazy_sfinae() {
#if defined(_LIBCPP_VERSION)
// This test requires libc++'s reduced arity initialization.
using T1 = ConstructibleFromT<std::pair<int, int>>;
using T2 = CtorAssertsT<int>;
std::pair<int, int> p(42, 100);
std::tuple<T1, T2> t(p);
assert(std::get<0>(t).value == p);
assert(std::get<1>(t).defaulted);
#endif
}
struct NonConstCopyable {
NonConstCopyable() = default;
explicit NonConstCopyable(int v) : value(v) {}
NonConstCopyable(NonConstCopyable&) = default;
NonConstCopyable(NonConstCopyable const&) = delete;
int value;
};
template <class T>
struct BlowsUpOnConstCopy {
BlowsUpOnConstCopy() = default;
constexpr BlowsUpOnConstCopy(BlowsUpOnConstCopy const&) {
static_assert(!std::is_same<T, T>::value, "");
}
BlowsUpOnConstCopy(BlowsUpOnConstCopy&) = default;
};
// Test the following constructors:
// (1) tuple(Types const&...)
// (2) tuple(UTypes&&...)
// Test that (1) short circuits before evaluating the copy constructor of the
// second argument. Constructor (2) should be selected.
void test_const_Types_lazy_sfinae()
{
NonConstCopyable v(42);
BlowsUpOnConstCopy<int> b;
std::tuple<NonConstCopyable, BlowsUpOnConstCopy<int>> t(v, b);
assert(std::get<0>(t).value == 42);
}
int main(int, char**) {
test_tuple_like_lazy_sfinae();
test_const_Types_lazy_sfinae();
return 0;
}
|
