40a6be4346
Some types that inherit from `view_interface` do not meet the preconditions. This came up during discussion in https://reviews.llvm.org/D112631. Currently, the behavior is IFNDR, but the preconditions can be easily checked, so let's do so. In particular, we know each public member function calls the `__derived()` private function, so we can do the check there. We intentionally do it as a `static_assert` instead of a `requires` clause to avoid hard erroring in some cases, such as with incomplete types. An example hard error is: ``` llvm-project/build/include/c++/v1/__ranges/view_interface.h:48:14: note: because 'sizeof(_Tp)' would be invalid: invalid application of 'sizeof' to an incomplete type 'MoveOnlyForwardRange' requires { sizeof(_Tp); } && ^ llvm-project/build/include/c++/v1/__ranges/view_interface.h:73:26: error: no matching member function for call to '__derived' return ranges::begin(__derived()) == ranges::end(__derived()); ^~~~~~~~~ llvm-project/libcxx/test/std/ranges/range.utility/view.interface/view.interface.pass.cpp:187:31: note: in instantiation of function template specialization 'std::ranges::view_interface<MoveOnlyForwardRange>::empty<Mov eOnlyForwardRange>' requested here assert(!std::move(moveOnly).empty()); ``` Reviewed By: Quuxplusone, Mordante, #libc Differential Revision: https://reviews.llvm.org/D112665
197 lines
6.1 KiB
C++
197 lines
6.1 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___RANGES_VIEW_INTERFACE_H
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#define _LIBCPP___RANGES_VIEW_INTERFACE_H
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#include <__config>
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#include <__debug>
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#include <__iterator/concepts.h>
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#include <__iterator/iterator_traits.h>
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#include <__iterator/prev.h>
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#include <__memory/pointer_traits.h>
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#include <__ranges/access.h>
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#include <__ranges/concepts.h>
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#include <__ranges/empty.h>
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#include <__ranges/enable_view.h>
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#include <concepts>
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#include <type_traits>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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#pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if !defined(_LIBCPP_HAS_NO_RANGES)
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namespace ranges {
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template<class _Tp>
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concept __can_empty = requires(_Tp __t) { ranges::empty(__t); };
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template<class _Tp>
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void __implicitly_convert_to(type_identity_t<_Tp>) noexcept;
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template<class _Derived>
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requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
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class view_interface : public view_base {
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_LIBCPP_HIDE_FROM_ABI
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constexpr _Derived& __derived() noexcept {
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static_assert(sizeof(_Derived) && derived_from<_Derived, view_interface> && view<_Derived>);
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return static_cast<_Derived&>(*this);
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}
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_LIBCPP_HIDE_FROM_ABI
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constexpr _Derived const& __derived() const noexcept {
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static_assert(sizeof(_Derived) && derived_from<_Derived, view_interface> && view<_Derived>);
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return static_cast<_Derived const&>(*this);
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}
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public:
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template<class _D2 = _Derived>
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty()
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noexcept(noexcept(__implicitly_convert_to<bool>(ranges::begin(__derived()) == ranges::end(__derived()))))
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requires forward_range<_D2>
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{
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return ranges::begin(__derived()) == ranges::end(__derived());
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}
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template<class _D2 = _Derived>
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const
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noexcept(noexcept(__implicitly_convert_to<bool>(ranges::begin(__derived()) == ranges::end(__derived()))))
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requires forward_range<const _D2>
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{
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return ranges::begin(__derived()) == ranges::end(__derived());
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}
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template<class _D2 = _Derived>
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_LIBCPP_HIDE_FROM_ABI
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constexpr explicit operator bool()
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noexcept(noexcept(ranges::empty(declval<_D2>())))
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requires __can_empty<_D2>
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{
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return !ranges::empty(__derived());
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}
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template<class _D2 = _Derived>
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_LIBCPP_HIDE_FROM_ABI
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constexpr explicit operator bool() const
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noexcept(noexcept(ranges::empty(declval<const _D2>())))
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requires __can_empty<const _D2>
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{
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return !ranges::empty(__derived());
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}
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template<class _D2 = _Derived>
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_LIBCPP_HIDE_FROM_ABI
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constexpr auto data()
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noexcept(noexcept(_VSTD::to_address(ranges::begin(__derived()))))
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requires contiguous_iterator<iterator_t<_D2>>
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{
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return _VSTD::to_address(ranges::begin(__derived()));
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}
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template<class _D2 = _Derived>
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_LIBCPP_HIDE_FROM_ABI
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constexpr auto data() const
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noexcept(noexcept(_VSTD::to_address(ranges::begin(__derived()))))
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requires range<const _D2> && contiguous_iterator<iterator_t<const _D2>>
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{
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return _VSTD::to_address(ranges::begin(__derived()));
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}
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template<class _D2 = _Derived>
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_LIBCPP_HIDE_FROM_ABI
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constexpr auto size()
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noexcept(noexcept(ranges::end(__derived()) - ranges::begin(__derived())))
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requires forward_range<_D2>
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&& sized_sentinel_for<sentinel_t<_D2>, iterator_t<_D2>>
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{
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return ranges::end(__derived()) - ranges::begin(__derived());
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}
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template<class _D2 = _Derived>
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_LIBCPP_HIDE_FROM_ABI
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constexpr auto size() const
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noexcept(noexcept(ranges::end(__derived()) - ranges::begin(__derived())))
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requires forward_range<const _D2>
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&& sized_sentinel_for<sentinel_t<const _D2>, iterator_t<const _D2>>
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{
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return ranges::end(__derived()) - ranges::begin(__derived());
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}
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template<class _D2 = _Derived>
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_LIBCPP_HIDE_FROM_ABI
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constexpr decltype(auto) front()
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noexcept(noexcept(*ranges::begin(__derived())))
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requires forward_range<_D2>
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{
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_LIBCPP_ASSERT(!empty(),
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"Precondition `!empty()` not satisfied. `.front()` called on an empty view.");
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return *ranges::begin(__derived());
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}
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template<class _D2 = _Derived>
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_LIBCPP_HIDE_FROM_ABI
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constexpr decltype(auto) front() const
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noexcept(noexcept(*ranges::begin(__derived())))
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requires forward_range<const _D2>
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{
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_LIBCPP_ASSERT(!empty(),
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"Precondition `!empty()` not satisfied. `.front()` called on an empty view.");
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return *ranges::begin(__derived());
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}
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template<class _D2 = _Derived>
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_LIBCPP_HIDE_FROM_ABI
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constexpr decltype(auto) back()
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noexcept(noexcept(*ranges::prev(ranges::end(__derived()))))
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requires bidirectional_range<_D2> && common_range<_D2>
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{
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_LIBCPP_ASSERT(!empty(),
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"Precondition `!empty()` not satisfied. `.back()` called on an empty view.");
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return *ranges::prev(ranges::end(__derived()));
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}
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template<class _D2 = _Derived>
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_LIBCPP_HIDE_FROM_ABI
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constexpr decltype(auto) back() const
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noexcept(noexcept(*ranges::prev(ranges::end(__derived()))))
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requires bidirectional_range<const _D2> && common_range<const _D2>
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{
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_LIBCPP_ASSERT(!empty(),
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"Precondition `!empty()` not satisfied. `.back()` called on an empty view.");
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return *ranges::prev(ranges::end(__derived()));
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}
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template<random_access_range _RARange = _Derived>
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_LIBCPP_HIDE_FROM_ABI
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constexpr decltype(auto) operator[](range_difference_t<_RARange> __index)
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noexcept(noexcept(ranges::begin(__derived())[__index]))
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{
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return ranges::begin(__derived())[__index];
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}
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template<random_access_range _RARange = const _Derived>
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_LIBCPP_HIDE_FROM_ABI
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constexpr decltype(auto) operator[](range_difference_t<_RARange> __index) const
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noexcept(noexcept(ranges::begin(__derived())[__index]))
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{
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return ranges::begin(__derived())[__index];
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}
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};
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}
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#endif // !defined(_LIBCPP_HAS_NO_RANGES)
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___RANGES_VIEW_INTERFACE_H
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