78 lines · cpp
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-exception6//7//===----------------------------------------------------------------------===//8 9// UNSUPPORTED: c++0310 11// This test ensures that std::tuple is lazy when it comes to checking whether12// the elements it is assigned from can be used to assign to the types in13// the tuple.14 15#include <tuple>16#include <array>17 18template <bool Enable, class ...Class>19constexpr typename std::enable_if<Enable, bool>::type BlowUp() {20 static_assert(Enable && sizeof...(Class) != sizeof...(Class), "");21 return true;22}23 24template<class T>25struct Fail {26 static_assert(sizeof(T) != sizeof(T), "");27 using type = void;28};29 30struct NoAssign {31 NoAssign() = default;32 NoAssign(NoAssign const&) = default;33 template <class T, class = typename std::enable_if<sizeof(T) != sizeof(T)>::type>34 NoAssign& operator=(T) { return *this; }35};36 37template <int>38struct DieOnAssign {39 DieOnAssign() = default;40 template <class T, class X = typename std::enable_if<!std::is_same<T, DieOnAssign>::value>::type,41 class = typename Fail<X>::type>42 DieOnAssign& operator=(T) {43 return *this;44 }45};46 47void test_arity_checks() {48 {49 using T = std::tuple<int, DieOnAssign<0>, int>;50 using P = std::pair<int, int>;51 static_assert(!std::is_assignable<T&, P const&>::value, "");52 }53 {54 using T = std::tuple<int, int, DieOnAssign<1> >;55 using A = std::array<int, 1>;56 static_assert(!std::is_assignable<T&, A const&>::value, "");57 }58}59 60void test_assignability_checks() {61 {62 using T1 = std::tuple<int, NoAssign, DieOnAssign<2> >;63 using T2 = std::tuple<long, long, long>;64 static_assert(!std::is_assignable<T1&, T2 const&>::value, "");65 }66 {67 using T1 = std::tuple<NoAssign, DieOnAssign<3> >;68 using T2 = std::pair<long, double>;69 static_assert(!std::is_assignable<T1&, T2 const&>::value, "");70 }71}72 73int main(int, char**) {74 test_arity_checks();75 test_assignability_checks();76 return 0;77}78