1//===----------------------------------------------------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is dual licensed under the MIT and the University of Illinois Open
6// Source Licenses. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// UNSUPPORTED: c++98, c++03
11
12// <tuple>
13
14// template <class... Types> class tuple;
15
16// template <class ...UTypes>
17//    EXPLICIT(...) tuple(UTypes&&...)
18
19// Check that the UTypes... ctor is properly disabled before evaluating any
20// SFINAE when the tuple-like copy/move ctor should *clearly* be selected
21// instead. This happens 'sizeof...(UTypes) == 1' and the first element of
22// 'UTypes...' is an instance of the tuple itself. See PR23256.
23
24#include <tuple>
25#include <memory>
26#include <type_traits>
27
28
29struct UnconstrainedCtor {
30  int value_;
31
32  UnconstrainedCtor() : value_(0) {}
33
34  // Blows up when instantiated for any type other than int. Because the ctor
35  // is constexpr it is instantiated by 'is_constructible' and 'is_convertible'
36  // for Clang based compilers. GCC does not instantiate the ctor body
37  // but it does instantiate the noexcept specifier and it will blow up there.
38  template <typename T>
39  constexpr UnconstrainedCtor(T value) noexcept(noexcept(value_ = value))
40      : value_(static_cast<int>(value))
41  {
42      static_assert(std::is_same<int, T>::value, "");
43  }
44};
45
46struct ExplicitUnconstrainedCtor {
47  int value_;
48
49  ExplicitUnconstrainedCtor() : value_(0) {}
50
51  template <typename T>
52  constexpr explicit ExplicitUnconstrainedCtor(T value)
53    noexcept(noexcept(value_ = value))
54      : value_(static_cast<int>(value))
55  {
56      static_assert(std::is_same<int, T>::value, "");
57  }
58
59};
60
61int main() {
62    typedef UnconstrainedCtor A;
63    typedef ExplicitUnconstrainedCtor ExplicitA;
64    {
65        static_assert(std::is_copy_constructible<std::tuple<A>>::value, "");
66        static_assert(std::is_move_constructible<std::tuple<A>>::value, "");
67        static_assert(std::is_copy_constructible<std::tuple<ExplicitA>>::value, "");
68        static_assert(std::is_move_constructible<std::tuple<ExplicitA>>::value, "");
69    }
70    {
71        static_assert(std::is_constructible<
72            std::tuple<A>,
73            std::allocator_arg_t, std::allocator<void>,
74            std::tuple<A> const&
75        >::value, "");
76        static_assert(std::is_constructible<
77            std::tuple<A>,
78            std::allocator_arg_t, std::allocator<void>,
79            std::tuple<A> &&
80        >::value, "");
81        static_assert(std::is_constructible<
82            std::tuple<ExplicitA>,
83            std::allocator_arg_t, std::allocator<void>,
84            std::tuple<ExplicitA> const&
85        >::value, "");
86        static_assert(std::is_constructible<
87            std::tuple<ExplicitA>,
88            std::allocator_arg_t, std::allocator<void>,
89            std::tuple<ExplicitA> &&
90        >::value, "");
91    }
92    {
93        std::tuple<A&&> t(std::forward_as_tuple(A{}));
94        ((void)t);
95        std::tuple<ExplicitA&&> t2(std::forward_as_tuple(ExplicitA{}));
96        ((void)t2);
97    }
98}
99