389a23c538
Resolves #148131 - Unlock `std::optional<T&>` implementation - Allow instantiations of `optional<T(&)(...)>` and `optional<T(&)[]>` but disables `value_or()` and `optional::iterator` + all `iterator` related functions - Update documentation - Update tests
70 lines
1.9 KiB
C++
70 lines
1.9 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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// REQUIRES: std-at-least-c++26
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// <optional>
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// constexpr iterator optional::begin() noexcept;
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// constexpr const_iterator optional::begin() const noexcept;
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#include <cassert>
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#include <iterator>
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#include <optional>
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#include <type_traits>
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#include <utility>
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template <typename T>
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constexpr bool test() {
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std::remove_reference_t<T> t = std::remove_reference_t<T>{};
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std::optional<T> opt{t};
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{ // begin() is marked noexcept
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static_assert(noexcept(opt.begin()));
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static_assert(noexcept(std::as_const(opt).begin()));
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}
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{ // Dereferencing an iterator at the beginning == indexing the 0th element, and that calling begin() again return the same iterator.
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auto iter1 = opt.begin();
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auto iter2 = std::as_const(opt).begin();
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assert(*iter1 == iter1[0]);
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assert(*iter2 == iter2[0]);
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assert(iter1 == opt.begin());
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assert(iter2 == std::as_const(opt).begin());
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}
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{ // Calling begin() multiple times on a disengaged optional returns the same iterator.
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std::optional<T> disengaged{std::nullopt};
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auto iter1 = disengaged.begin();
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auto iter2 = std::as_const(disengaged).begin();
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assert(iter1 == disengaged.begin());
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assert(iter2 == std::as_const(disengaged).begin());
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}
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return true;
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}
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constexpr bool tests() {
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assert(test<int>());
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assert(test<char>());
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assert(test<const int>());
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assert(test<const char>());
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assert(test<int&>());
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assert(test<char&>());
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assert(test<const int&>());
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assert(test<const char&>());
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return true;
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}
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int main(int, char**) {
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assert(tests());
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static_assert(tests());
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return 0;
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}
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