1679b27959
The exposition-only type trait `pair-like` includes `ranges::subrange`, but in every single case excludes `ranges::subrange` from the list. This patch introduces two new traits `__tuple_like_no_subrange` and `__pair_like_no_subrange`, which exclude `ranges::subrange` from the possible matches. `__pair_like` is no longer required, and thus removed. `__tuple_like` is implemented as `__tuple_like_no_subrange` or a `ranges::subrange` specialization.
75 lines
2.5 KiB
C++
75 lines
2.5 KiB
C++
//===----------------------------------------------------------------------===//
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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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// UNSUPPORTED: c++03, c++11, c++14, c++17
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// concept checking
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//
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// template<class T, size_t N>
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// concept has-tuple-element =
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// tuple-like<T> && N < tuple_size_v<T>;
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//
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// template<class T, size_t N>
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// concept returnable-element =
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// is_reference_v<T> || move_constructible<tuple_element_t<N, T>>;
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//
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// template<input_range V, size_t N>
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// requires view<V> && has-tuple-element<range_value_t<V>, N> &&
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// has-tuple-element<remove_reference_t<range_reference_t<V>>, N> &&
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// returnable-element<range_reference_t<V>, N>
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// class elements_view;
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#include <array>
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#include <concepts>
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#include <tuple>
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#include <ranges>
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#include <utility>
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#include "test_iterators.h"
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template <class It>
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using Range = std::ranges::subrange<It, sentinel_wrapper<It>>;
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template <class V, std::size_t N>
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concept HasElementsView = requires { typename std::ranges::elements_view<V, N>; };
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static_assert(HasElementsView<Range<std::ranges::subrange<int*>*>, 0>);
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static_assert(HasElementsView<Range<std::pair<int, int>*>, 1>);
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static_assert(HasElementsView<Range<std::tuple<int, int, int>*>, 2>);
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static_assert(HasElementsView<Range<std::array<int, 4>*>, 3>);
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// !view<V>
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static_assert(!std::ranges::view<std::array<std::tuple<int>, 1>>);
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static_assert(!HasElementsView<std::array<std::tuple<int>, 1>, 0>);
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// !input_range
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static_assert(!std::ranges::input_range<Range<cpp20_output_iterator<std::tuple<int>*>>>);
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static_assert(!HasElementsView<Range<cpp20_output_iterator<std::tuple<int>*>>, 0>);
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// !tuple-like
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static_assert(!HasElementsView<Range<int*>, 1>);
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// !(N < tuple_size_v<T>)
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static_assert(!(2 < std::tuple_size_v< std::pair<int, int>>));
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static_assert(!HasElementsView<Range<std::pair<int, int>*>, 2>);
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// ! (is_reference_v<T> || move_constructible<tuple_element_t<N, T>>)
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struct NonMovable {
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NonMovable(int) {}
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NonMovable(NonMovable&&) = delete;
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};
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static_assert(!std::move_constructible<NonMovable>);
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using NonMovableGenerator =
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decltype(std::views::iota(0, 1) | std::views::transform([](int) {
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return std::pair<NonMovable, int>{1, 1};
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}));
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static_assert(!HasElementsView<NonMovableGenerator, 0>);
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static_assert(HasElementsView<NonMovableGenerator, 1>);
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