1ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith// RUN: %clang_cc1 -std=c++11 %s -fsyntax-only -fcxx-exceptions 2ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 3ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithtemplate<typename T> struct remove_reference { typedef T type; }; 4ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithtemplate<typename T> struct remove_reference<T&> { typedef T type; }; 5ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithtemplate<typename T> struct remove_reference<T&&> { typedef T type; }; 6ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 7ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithtemplate<typename T> constexpr T &&forward(typename remove_reference<T>::type &t) noexcept { return static_cast<T&&>(t); } 8ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithtemplate<typename T> constexpr T &&forward(typename remove_reference<T>::type &&t) noexcept { return static_cast<T&&>(t); } 9ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithtemplate<typename T> constexpr typename remove_reference<T>::type &&move(T &&t) noexcept { return static_cast<typename remove_reference<T>::type&&>(t); } 10ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 11ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithtemplate<typename T> T declval() noexcept; 12ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 13ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithnamespace detail { 14ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<unsigned N> struct select {}; // : integral_constant<unsigned, N> {}; 15ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<typename T> struct type {}; 16ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 17ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<typename...T> union either_impl; 18ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 19ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<> union either_impl<> { 20ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith void get(...); 21ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith void destroy(...) { throw "logic_error"; } 22ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith }; 23ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 24ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<typename T, typename...Ts> union either_impl<T, Ts...> { 25ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith private: 26ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith T val; 27ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith either_impl<Ts...> rest; 28ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith typedef either_impl<Ts...> rest_t; 29ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 30ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith public: 31ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith constexpr either_impl(select<0>, T &&t) : val(move(t)) {} 32ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 33ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<unsigned N, typename U> 34ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith constexpr either_impl(select<N>, U &&u) : rest(select<N-1>(), move(u)) {} 35ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 36ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith constexpr static unsigned index(type<T>) { return 0; } 37ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<typename U> 38ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith constexpr static unsigned index(type<U> t) { 39ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith return decltype(rest)::index(t) + 1; 40ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith } 41ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 42ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith void destroy(unsigned elem) { 43ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith if (elem) 44ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith rest.destroy(elem - 1); 45ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith else 46ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith val.~T(); 47ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith } 48ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 49ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith constexpr const T &get(select<0>) { return val; } 50ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<unsigned N> constexpr const decltype(static_cast<const rest_t&>(rest).get(select<N-1>{})) get(select<N>) { 51ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith return rest.get(select<N-1>{}); 52ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith } 53ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith }; 54ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith} 55ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 56ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithtemplate<typename T> 57ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithstruct a { 58ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith T value; 59ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<typename...U> 60ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith constexpr a(U &&...u) : value{forward<U>(u)...} {} 61ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith}; 62ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithtemplate<typename T> using an = a<T>; 63ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 64ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithtemplate<typename T, typename U> T throw_(const U &u) { throw u; } 65ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 66ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithtemplate<typename...T> 67ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithclass either { 68ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith unsigned elem; 69ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith detail::either_impl<T...> impl; 70ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith typedef decltype(impl) impl_t; 71ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 72ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithpublic: 73ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<typename U> 74ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith constexpr either(a<U> &&t) : 75ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith elem(impl_t::index(detail::type<U>())), 76ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith impl(detail::select<impl_t::index(detail::type<U>())>(), move(t.value)) {} 77ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 78ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith // Destruction disabled to allow use in a constant expression. 79ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith // FIXME: declare a destructor iff any element has a nontrivial destructor 80ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith //~either() { impl.destroy(elem); } 81ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 82ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith constexpr unsigned index() noexcept { return elem; } 83ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 84ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<unsigned N> using const_get_result = 85ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith decltype(static_cast<const impl_t&>(impl).get(detail::select<N>{})); 86ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 87ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<unsigned N> 88ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith constexpr const_get_result<N> get() { 89ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith // Can't just use throw here, since that makes the conditional a prvalue, 90ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith // which means we return a reference to a temporary. 91ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith return (elem != N ? throw_<const_get_result<N>>("bad_either_get") 92ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith : impl.get(detail::select<N>{})); 93ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith } 94ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 95ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith template<typename U> 96ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith constexpr const U &get() { 97ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith return get<impl_t::index(detail::type<U>())>(); 98ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith } 99ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith}; 100ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 101ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithtypedef either<int, char, double> icd; 102ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithconstexpr icd icd1 = an<int>(4); 103ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithconstexpr icd icd2 = a<char>('x'); 104ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithconstexpr icd icd3 = a<double>(6.5); 105ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 106ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithstatic_assert(icd1.get<int>() == 4, ""); 107ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithstatic_assert(icd2.get<char>() == 'x', ""); 108ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithstatic_assert(icd3.get<double>() == 6.5, ""); 109ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 110ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithstruct non_triv { 111ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith constexpr non_triv() : n(5) {} 112ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith int n; 113ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith}; 114ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithconstexpr either<const icd*, non_triv> icd4 = a<const icd*>(&icd2); 115ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithconstexpr either<const icd*, non_triv> icd5 = a<non_triv>(); 116ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smith 117ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithstatic_assert(icd4.get<const icd*>()->get<char>() == 'x', ""); 118ec92bc78979aae6ec436fe51d082f7467e6f96c0Richard Smithstatic_assert(icd5.get<non_triv>().n == 5, ""); 119