1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4//                     The LLVM Compiler Infrastructure
5//
6// This file is dual licensed under the MIT and the University of Illinois Open
7// Source Licenses. See LICENSE.TXT for details.
8//
9//===----------------------------------------------------------------------===//
10
11// UNSUPPORTED: c++98, c++03
12
13// <tuple>
14
15// template <class TupleLike> tuple(TupleLike&&); // libc++ extension
16
17// See llvm.org/PR31384
18#include <tuple>
19#include <cassert>
20
21int count = 0;
22
23struct Explicit {
24  Explicit() = default;
25  explicit Explicit(int) {}
26};
27
28struct Implicit {
29  Implicit() = default;
30  Implicit(int) {}
31};
32
33template<class T>
34struct Derived : std::tuple<T> {
35  using std::tuple<T>::tuple;
36  template<class U>
37  operator std::tuple<U>() && { ++count; return {}; }
38};
39
40
41template<class T>
42struct ExplicitDerived : std::tuple<T> {
43  using std::tuple<T>::tuple;
44  template<class U>
45  explicit operator std::tuple<U>() && { ++count; return {}; }
46};
47
48int main() {
49  {
50    std::tuple<Explicit> foo = Derived<int>{42}; ((void)foo);
51    assert(count == 1);
52    std::tuple<Explicit> bar(Derived<int>{42}); ((void)bar);
53    assert(count == 2);
54  }
55  count = 0;
56  {
57    std::tuple<Implicit> foo = Derived<int>{42}; ((void)foo);
58    assert(count == 1);
59    std::tuple<Implicit> bar(Derived<int>{42}); ((void)bar);
60    assert(count == 2);
61  }
62  count = 0;
63  {
64    static_assert(!std::is_convertible<
65        ExplicitDerived<int>, std::tuple<Explicit>>::value, "");
66    std::tuple<Explicit> bar(ExplicitDerived<int>{42}); ((void)bar);
67    assert(count == 1);
68  }
69  count = 0;
70  {
71    // FIXME: Libc++ incorrectly rejects this code.
72#ifndef _LIBCPP_VERSION
73    std::tuple<Implicit> foo = ExplicitDerived<int>{42}; ((void)foo);
74    static_assert(std::is_convertible<
75        ExplicitDerived<int>, std::tuple<Implicit>>::value,
76        "correct STLs accept this");
77#else
78    static_assert(!std::is_convertible<
79        ExplicitDerived<int>, std::tuple<Implicit>>::value,
80        "libc++ incorrectly rejects this");
81#endif
82    assert(count == 0);
83    std::tuple<Implicit> bar(ExplicitDerived<int>{42}); ((void)bar);
84    assert(count == 1);
85  }
86  count = 0;
87
88}
89