emplace.pass.cpp (1906B)
1 //===----------------------------------------------------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is dual licensed under the MIT and the University of Illinois Open 6 // Source Licenses. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 // UNSUPPORTED: c++98, c++03 11 12 // <queue> 13 14 // template <class... Args> decltype(auto) emplace(Args&&... args); 15 // return type is 'decltype(auto)' in C++17; 'void' before 16 // whatever the return type of the underlying container's emplace_back() returns. 17 18 19 #include <queue> 20 #include <cassert> 21 #include <list> 22 23 #include "test_macros.h" 24 25 #include "../../../Emplaceable.h" 26 27 template <typename Queue> 28 void test_return_type() { 29 typedef typename Queue::container_type Container; 30 typedef typename Container::value_type value_type; 31 typedef decltype(std::declval<Queue>().emplace(std::declval<value_type &>())) queue_return_type; 32 33 #if TEST_STD_VER > 14 34 typedef decltype(std::declval<Container>().emplace_back(std::declval<value_type>())) container_return_type; 35 static_assert(std::is_same<queue_return_type, container_return_type>::value, ""); 36 #else 37 static_assert(std::is_same<queue_return_type, void>::value, ""); 38 #endif 39 } 40 41 int main() 42 { 43 test_return_type<std::queue<int> > (); 44 test_return_type<std::queue<int, std::list<int> > > (); 45 46 std::queue<Emplaceable> q; 47 #if TEST_STD_VER > 14 48 typedef Emplaceable T; 49 T& r1 = q.emplace(1, 2.5); 50 assert(&r1 == &q.back()); 51 T& r2 = q.emplace(2, 3.5); 52 assert(&r2 == &q.back()); 53 T& r3 = q.emplace(3, 4.5); 54 assert(&r3 == &q.back()); 55 assert(&r1 == &q.front()); 56 #else 57 q.emplace(1, 2.5); 58 q.emplace(2, 3.5); 59 q.emplace(3, 4.5); 60 #endif 61 62 assert(q.size() == 3); 63 assert(q.front() == Emplaceable(1, 2.5)); 64 assert(q.back() == Emplaceable(3, 4.5)); 65 }