PR libstdc++/90165 constrain variant(T&&) constructor
Also refactor some constraints slightly to be more readable. PR libstdc++/90165 * include/std/variant (variant::__not_self): New helper for the is_same_v<remove_cvref_t<T>, variant>==false constraints. (variant::__to_type_impl): Remove. (variant::__to_type): Add default argument to check pack size, instead of using __to_type_impl. (variant::__accepted_type): Add default argument using __not_self. (variant::__is_in_place_tag, variant::__not_in_place_tag): New helpers for variant(T&&) constructor constraint. (variant::variant(T&&)): Use __not_in_place_tag in constraints. Extract __accepted_type into a named template parameter for reuse in other constraints and in the exception specification. (variant::variant(in_place_type_t<T>, Args&&...)) (variant::variant(in_place_type_t<T>, initializer_list<U>, Args&&...)) (variant::variant(in_place_index_t<T>, Args&&...)) (variant::variant(in_place_index_t<T>, initializer_list<U>, Args&&...)) (variant::operator=T&&)): Remove redundant && from trait arguments. * testsuite/20_util/variant/compile.cc: Check variant(T&&) constructor isn't used for in_place_type or in_place_index arguments. From-SVN: r270509
This commit is contained in:
Jonathan Wakely
Jonathan Wakely
parent
82e8c3da74
commit
06715e1cfb
3 changed files with 64 additions and 27 deletions
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@ -1,5 +1,25 @@
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2019-04-23 Jonathan Wakely <jwakely@redhat.com>
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PR libstdc++/90165
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* include/std/variant (variant::__not_self): New helper for the
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is_same_v<remove_cvref_t<T>, variant>==false constraints.
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(variant::__to_type_impl): Remove.
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(variant::__to_type): Add default argument to check pack size, instead
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of using __to_type_impl.
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(variant::__accepted_type): Add default argument using __not_self.
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(variant::__is_in_place_tag, variant::__not_in_place_tag): New helpers
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for variant(T&&) constructor constraint.
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(variant::variant(T&&)): Use __not_in_place_tag in constraints.
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Extract __accepted_type into a named template parameter for reuse in
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other constraints and in the exception specification.
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(variant::variant(in_place_type_t<T>, Args&&...))
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(variant::variant(in_place_type_t<T>, initializer_list<U>, Args&&...))
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(variant::variant(in_place_index_t<T>, Args&&...))
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(variant::variant(in_place_index_t<T>, initializer_list<U>, Args&&...))
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(variant::operator=T&&)): Remove redundant && from trait arguments.
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* testsuite/20_util/variant/compile.cc: Check variant(T&&) constructor
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isn't used for in_place_type or in_place_index arguments.
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* include/std/type_traits (unwrap_reference_t): Define for C++2a.
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(unwrap_ref_decay): Remove inheritance from unwrap_reference.
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* testsuite/20_util/unwrap_reference/1.cc: Adjust test to use alias.
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@ -1284,6 +1284,10 @@ namespace __variant
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__detail::__variant::_Traits<_Types...>::_S_default_ctor,
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variant<_Types...>>;
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template<typename _Tp>
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static constexpr bool __not_self
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= !is_same_v<__remove_cvref_t<_Tp>, variant>;
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template<typename _Tp>
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static constexpr bool
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__exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>;
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@ -1292,17 +1296,10 @@ namespace __variant
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static constexpr size_t __accepted_index =
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__detail::__variant::__accepted_index<_Tp&&, variant>::value;
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template<size_t _Np, bool = _Np < sizeof...(_Types)>
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struct __to_type_impl;
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template<size_t _Np, typename = enable_if_t<(_Np < sizeof...(_Types))>>
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using __to_type = variant_alternative_t<_Np, variant>;
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template<size_t _Np>
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struct __to_type_impl<_Np, true>
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{ using type = variant_alternative_t<_Np, variant>; };
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template<size_t _Np>
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using __to_type = typename __to_type_impl<_Np>::type;
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template<typename _Tp>
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template<typename _Tp, typename = enable_if_t<__not_self<_Tp>>>
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using __accepted_type = __to_type<__accepted_index<_Tp>>;
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template<typename _Tp>
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@ -1311,6 +1308,17 @@ namespace __variant
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using _Traits = __detail::__variant::_Traits<_Types...>;
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template<typename _Tp>
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struct __is_in_place_tag : false_type { };
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template<typename _Tp>
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struct __is_in_place_tag<in_place_type_t<_Tp>> : true_type { };
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template<size_t _Np>
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struct __is_in_place_tag<in_place_index_t<_Np>> : true_type { };
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template<typename _Tp>
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static constexpr bool __not_in_place_tag
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= !__is_in_place_tag<__remove_cvref_t<_Tp>>::value;
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public:
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variant() = default;
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variant(const variant& __rhs) = default;
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@ -1320,20 +1328,21 @@ namespace __variant
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~variant() = default;
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template<typename _Tp,
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typename = enable_if_t<!is_same_v<decay_t<_Tp>, variant>>,
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typename = enable_if_t<(sizeof...(_Types)>0)>,
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typename = enable_if_t<__exactly_once<__accepted_type<_Tp&&>>
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&& is_constructible_v<__accepted_type<_Tp&&>, _Tp&&>>>
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typename = enable_if_t<sizeof...(_Types) != 0>,
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typename = enable_if_t<__not_in_place_tag<_Tp>>,
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typename _Tj = __accepted_type<_Tp&&>,
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typename = enable_if_t<__exactly_once<_Tj>
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&& is_constructible_v<_Tj, _Tp>>>
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constexpr
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variant(_Tp&& __t)
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noexcept(is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp&&>)
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noexcept(is_nothrow_constructible_v<_Tj, _Tp>)
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: variant(in_place_index<__accepted_index<_Tp&&>>,
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std::forward<_Tp>(__t))
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{ }
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template<typename _Tp, typename... _Args,
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typename = enable_if_t<__exactly_once<_Tp>
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&& is_constructible_v<_Tp, _Args&&...>>>
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&& is_constructible_v<_Tp, _Args...>>>
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constexpr explicit
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variant(in_place_type_t<_Tp>, _Args&&... __args)
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: variant(in_place_index<__index_of<_Tp>>,
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@ -1342,8 +1351,8 @@ namespace __variant
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template<typename _Tp, typename _Up, typename... _Args,
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typename = enable_if_t<__exactly_once<_Tp>
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&& is_constructible_v<
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_Tp, initializer_list<_Up>&, _Args&&...>>>
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&& is_constructible_v<_Tp,
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initializer_list<_Up>&, _Args...>>>
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constexpr explicit
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variant(in_place_type_t<_Tp>, initializer_list<_Up> __il,
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_Args&&... __args)
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@ -1352,8 +1361,8 @@ namespace __variant
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{ }
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template<size_t _Np, typename... _Args,
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typename = enable_if_t<
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is_constructible_v<__to_type<_Np>, _Args&&...>>>
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typename _Tp = __to_type<_Np>,
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typename = enable_if_t<is_constructible_v<_Tp, _Args...>>>
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constexpr explicit
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variant(in_place_index_t<_Np>, _Args&&... __args)
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: _Base(in_place_index<_Np>, std::forward<_Args>(__args)...),
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@ -1361,8 +1370,10 @@ namespace __variant
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{ }
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template<size_t _Np, typename _Up, typename... _Args,
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typename = enable_if_t<is_constructible_v<__to_type<_Np>,
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initializer_list<_Up>&, _Args&&...>>>
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typename _Tp = __to_type<_Np>,
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typename = enable_if_t<is_constructible_v<_Tp,
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initializer_list<_Up>&,
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_Args...>>>
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constexpr explicit
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variant(in_place_index_t<_Np>, initializer_list<_Up> __il,
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_Args&&... __args)
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@ -1372,12 +1383,12 @@ namespace __variant
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template<typename _Tp>
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enable_if_t<__exactly_once<__accepted_type<_Tp&&>>
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&& is_constructible_v<__accepted_type<_Tp&&>, _Tp&&>
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&& is_assignable_v<__accepted_type<_Tp&&>&, _Tp&&>
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&& !is_same_v<decay_t<_Tp>, variant>, variant&>
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&& is_constructible_v<__accepted_type<_Tp&&>, _Tp>
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&& is_assignable_v<__accepted_type<_Tp&&>&, _Tp>,
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variant&>
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operator=(_Tp&& __rhs)
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noexcept(is_nothrow_assignable_v<__accepted_type<_Tp&&>&, _Tp&&>
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&& is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp&&>)
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noexcept(is_nothrow_assignable_v<__accepted_type<_Tp&&>&, _Tp>
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&& is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp>)
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{
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constexpr auto __index = __accepted_index<_Tp&&>;
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if (index() == __index)
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@ -144,10 +144,15 @@ void arbitrary_ctor()
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static_assert(noexcept(variant<int, DefaultNoexcept>(DefaultNoexcept{})));
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}
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struct none { none() = delete; };
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struct any { template <typename T> any(T&&) {} };
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void in_place_index_ctor()
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{
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variant<string, string> a(in_place_index<0>, "a");
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variant<string, string> b(in_place_index<1>, {'a'});
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static_assert(!is_constructible_v<variant<none, any>, std::in_place_index_t<0>>, "PR libstdc++/90165");
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}
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void in_place_type_ctor()
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@ -155,6 +160,7 @@ void in_place_type_ctor()
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variant<int, string, int> a(in_place_type<string>, "a");
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variant<int, string, int> b(in_place_type<string>, {'a'});
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static_assert(!is_constructible_v<variant<string, string>, in_place_type_t<string>, const char*>);
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static_assert(!is_constructible_v<variant<none, any>, std::in_place_type_t<none>>, "PR libstdc++/90165");
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}
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void dtor()
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