| // PR c++/81933 |
| // { dg-do compile { target c++14 } } |
| |
| namespace std { |
| template <typename _Tp> struct __decay_and_strip { typedef _Tp __type; }; |
| template <int> struct enable_if { typedef int type; }; |
| template <typename _Head> struct _Head_base { |
| constexpr _Head_base(_Head) {} |
| }; |
| template <unsigned long, typename...> struct _Tuple_impl; |
| template <unsigned long _Idx, typename _Head, typename... _Tail> |
| struct _Tuple_impl<_Idx, _Head, _Tail...> : _Tuple_impl<1, _Tail...>, // { dg-warning "direct base" } |
| _Head_base<_Head> { |
| typedef _Tuple_impl<1, _Tail...> _Inherited; |
| typedef _Head_base<_Head> _Base; |
| constexpr _Tuple_impl(_Head __head, _Tail... __tail) |
| : _Inherited(__tail...), _Base(__head) {} |
| _Tuple_impl(const _Tuple_impl &) = default; |
| _Tuple_impl(_Tuple_impl &&); |
| }; |
| template <unsigned long _Idx, typename _Head> |
| struct _Tuple_impl<_Idx, _Head> : _Head_base<_Head> { |
| typedef _Head_base<_Head> _Base; |
| constexpr _Tuple_impl(_Head __head) : _Base(__head) {} |
| }; |
| template <int> struct _TC { |
| static constexpr bool _NotSameTuple() { return true; } |
| }; |
| template <typename... _Elements> class tuple : _Tuple_impl<0, _Elements...> { |
| typedef _Tuple_impl<0, _Elements...> _Inherited; |
| |
| public: |
| template <typename... _UElements, |
| enable_if<_TC<1>::_NotSameTuple()>::type = false> |
| constexpr tuple(_UElements... __elements) : _Inherited(__elements...) {} |
| tuple(const tuple &) = default; |
| }; |
| template <typename... _Elements> |
| constexpr tuple<typename __decay_and_strip<_Elements>::__type...> |
| make_tuple(_Elements... __args) { |
| typedef tuple<typename __decay_and_strip<_Elements>::__type...> __result_type; |
| return __result_type(__args...); |
| } |
| } |
| struct any_udt {}; |
| template <typename... Tuples> constexpr auto flatten(Tuples... tuples) { |
| auto all = std::make_tuple(tuples...); |
| auto flat(all); |
| return flat; |
| } |
| constexpr auto fail = flatten(any_udt{}, any_udt{}); |