libcxx/test/std/containers/container.adaptors/queue/queue.defn/emplace.pass.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-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // UNSUPPORTED: c++03
  10
  11 // <queue>
  12
  13 // template <class... Args> decltype(auto) emplace(Args&&... args);
  14 // return type is 'decltype(auto)' in C++17; 'void' before
  15 // whatever the return type of the underlying container's emplace_back() returns.
  16
  17
  18 #include <queue>
  19 #include <cassert>
  20 #include <list>
  21
  22 #include "test_macros.h"
  23
  24 #include "../../../Emplaceable.h"
  25
  26 template <typename Queue>
  27 void test_return_type() {
  28     typedef typename Queue::container_type Container;
  29     typedef typename Container::value_type value_type;
  30     typedef decltype(std::declval<Queue>().emplace(std::declval<value_type &>())) queue_return_type;
  31
  32 #if TEST_STD_VER > 14
  33     typedef decltype(std::declval<Container>().emplace_back(std::declval<value_type>())) container_return_type;
  34     static_assert(std::is_same<queue_return_type, container_return_type>::value, "");
  35 #else
  36     static_assert(std::is_same<queue_return_type, void>::value, "");
  37 #endif
  38 }
  39
  40 int main(int, char**)
  41 {
  42     test_return_type<std::queue<int> > ();
  43     test_return_type<std::queue<int, std::list<int> > > ();
  44
  45     std::queue<Emplaceable> q;
  46 #if TEST_STD_VER > 14
  47     typedef Emplaceable T;
  48     T& r1 = q.emplace(1, 2.5);
  49     assert(&r1 == &q.back());
  50     T& r2 = q.emplace(2, 3.5);
  51     assert(&r2 == &q.back());
  52     T& r3 = q.emplace(3, 4.5);
  53     assert(&r3 == &q.back());
  54     assert(&r1 == &q.front());
  55 #else
  56     q.emplace(1, 2.5);
  57     q.emplace(2, 3.5);
  58     q.emplace(3, 4.5);
  59 #endif
  60
  61     assert(q.size() == 3);
  62     assert(q.front() == Emplaceable(1, 2.5));
  63     assert(q.back() == Emplaceable(3, 4.5));
  64
  65   return 0;
  66 }