94461822c7
`subrange` is also a `tuple-like`. To avoid the add entire `subrange` dependencies to `tuple-like`, we need forward declaration of `subrange`. However, the class template constraints of `subrange` currently requires `__iterator/concepts.h`, which requires `<concepts>`. The problem is that currently `tuple-like` is used in several different places, including libc++ extension for pair constructors. we don't want to add `<concepts>` to pair and other stuff. So this change also created several small headers that `subrange`'s declaration needed inside `__iterator/concepts/` Differential Revision: https://reviews.llvm.org/D136268
89 lines
2.6 KiB
C++
89 lines
2.6 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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// constexpr auto begin() requires (!simple-view<V>)
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// constexpr auto begin() const requires range<const V>
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#include <cassert>
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#include <concepts>
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#include <ranges>
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#include <tuple>
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#include <utility>
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#include "types.h"
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template <class T>
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concept HasConstBegin = requires(const T ct) { ct.begin(); };
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template <class T>
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concept HasBegin = requires(T t) { t.begin(); };
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template <class T>
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concept HasConstAndNonConstBegin =
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HasConstBegin<T> &&
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// because const begin and non-const begin returns different types (iterator<true>, iterator<false>)
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requires(T t, const T ct) { requires !std::same_as<decltype(t.begin()), decltype(ct.begin())>; };
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template <class T>
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concept HasOnlyNonConstBegin = HasBegin<T> && !HasConstBegin<T>;
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template <class T>
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concept HasOnlyConstBegin = HasConstBegin<T> && !HasConstAndNonConstBegin<T>;
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struct NoConstBeginView : TupleBufferView {
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using TupleBufferView::TupleBufferView;
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constexpr std::tuple<int>* begin() { return buffer_; }
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constexpr std::tuple<int>* end() { return buffer_ + size_; }
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};
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// simple-view<V>
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static_assert(HasOnlyConstBegin<std::ranges::elements_view<SimpleCommon, 0>>);
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// !simple-view<V> && range<const V>
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static_assert(HasConstAndNonConstBegin<std::ranges::elements_view<NonSimpleCommon, 0>>);
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// !range<const V>
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static_assert(HasOnlyNonConstBegin<std::ranges::elements_view<NoConstBeginView, 0>>);
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constexpr bool test() {
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std::tuple<int> buffer[] = {{1}, {2}};
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{
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// underlying iterator should be pointing to the first element
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auto ev = std::views::elements<0>(buffer);
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auto iter = ev.begin();
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assert(&(*iter) == &std::get<0>(buffer[0]));
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}
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{
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// underlying range models simple-view
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auto v = std::views::elements<0>(SimpleCommon{buffer});
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static_assert(std::is_same_v<decltype(v.begin()), decltype(std::as_const(v).begin())>);
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assert(v.begin() == std::as_const(v).begin());
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auto&& r = *std::as_const(v).begin();
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assert(&r == &std::get<0>(buffer[0]));
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}
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{
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// underlying const R is not a range
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auto v = std::views::elements<0>(NoConstBeginView{buffer});
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auto&& r = *v.begin();
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assert(&r == &std::get<0>(buffer[0]));
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}
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return true;
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}
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int main(int, char**) {
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test();
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static_assert(test());
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return 0;
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}
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