1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20 10 11 // template<class... Args> 12 // constexpr T& emplace(Args&&... args) noexcept; 13 // Constraints: is_nothrow_constructible_v<T, Args...> is true. 14 // 15 // Effects: Equivalent to: 16 // if (has_value()) { 17 // destroy_at(addressof(val)); 18 // } else { 19 // destroy_at(addressof(unex)); 20 // has_val = true; 21 // } 22 // return *construct_at(addressof(val), std::forward<Args>(args)...); 23 24 #include <cassert> 25 #include <concepts> 26 #include <expected> 27 #include <type_traits> 28 #include <utility> 29 30 #include "../../types.h" 31 #include "test_macros.h" 32 33 template <class T, class... Args> 34 concept CanEmplace = requires(T t, Args&&... args) { t.emplace(std::forward<Args>(args)...); }; 35 36 static_assert(CanEmplace<std::expected<int, int>, int>); 37 38 template <bool Noexcept> 39 struct CtorFromInt { 40 CtorFromInt(int) noexcept(Noexcept); 41 CtorFromInt(int, int) noexcept(Noexcept); 42 }; 43 44 static_assert(CanEmplace<std::expected<CtorFromInt<true>, int>, int>); 45 static_assert(CanEmplace<std::expected<CtorFromInt<true>, int>, int, int>); 46 static_assert(!CanEmplace<std::expected<CtorFromInt<false>, int>, int>); 47 static_assert(!CanEmplace<std::expected<CtorFromInt<false>, int>, int, int>); 48 49 constexpr bool test() { 50 // has_value 51 { 52 BothNoexcept::state oldState{}; 53 BothNoexcept::state newState{}; 54 std::expected<BothNoexcept, int> e(std::in_place, oldState, 5); 55 decltype(auto) x = e.emplace(newState, 10); 56 static_assert(std::same_as<decltype(x), BothNoexcept&>); 57 assert(&x == &(*e)); 58 59 assert(oldState.dtorCalled); 60 assert(e.has_value()); 61 assert(e.value().data_ == 10); 62 } 63 64 // !has_value 65 { 66 BothMayThrow::state oldState{}; 67 std::expected<int, BothMayThrow> e(std::unexpect, oldState, 5); 68 decltype(auto) x = e.emplace(10); 69 static_assert(std::same_as<decltype(x), int&>); 70 assert(&x == &(*e)); 71 72 assert(oldState.dtorCalled); 73 assert(e.has_value()); 74 assert(e.value() == 10); 75 } 76 77 // TailClobberer 78 { 79 std::expected<TailClobberer<0>, bool> e(std::unexpect); 80 e.emplace(); 81 assert(e.has_value()); 82 } 83 84 // CheckForInvalidWrites 85 { 86 { 87 CheckForInvalidWrites<true> e; 88 e.emplace(); 89 assert(e.check()); 90 } 91 { 92 CheckForInvalidWrites<false> e; 93 e.emplace(); 94 assert(e.check()); 95 } 96 } 97 98 return true; 99 } 100 101 int main(int, char**) { 102 test(); 103 static_assert(test()); 104 return 0; 105 } 106