ceph/src/boost/libs/hana/test/tuple/cnstr.trap.cpp

   1 // Copyright Louis Dionne 2013-2016
   2 // Distributed under the Boost Software License, Version 1.0.
   3 // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   4
   5 #include <boost/hana/tuple.hpp>
   6
   7 #include <utility>
   8 namespace hana = boost::hana;
   9
  10
  11 // Make sure that the tuple(Yn&&...) is not preferred over the
  12 // tuple(tuple<Yn...> const&) and the tuple(tuple<Yn...>&&)
  13 // constructors when copy-constructing a tuple with a single
  14 // element that can be constructed from tuple<Yn...> const& and
  15 // tuple<Yn...>&&, respectively.
  16
  17 struct Trap1 {
  18     Trap1() = default;
  19     Trap1(Trap1 const&) = default;
  20     Trap1(Trap1&) = default;
  21     Trap1(Trap1&&) = default;
  22
  23     template <typename X>
  24     Trap1(X&&) {
  25         static_assert(sizeof(X) && false,
  26         "this constructor must not be instantiated");
  27     }
  28 };
  29
  30 struct Trap2 {
  31     Trap2() = default;
  32     Trap2(Trap2 const&) = default;
  33     Trap2(Trap2&) = default;
  34     Trap2(Trap2&&) = default;
  35
  36     template <typename X>
  37     Trap2(X) { // not by reference
  38         static_assert(sizeof(X) && false,
  39         "this constructor must not be instantiated");
  40     }
  41 };
  42
  43 int main() {
  44     {
  45         hana::tuple<Trap1> tuple{};
  46         hana::tuple<Trap1> implicit_copy = tuple;
  47         hana::tuple<Trap1> explicit_copy(tuple);
  48         hana::tuple<Trap1> implicit_move = std::move(tuple);
  49         hana::tuple<Trap1> explicit_move(std::move(tuple));
  50
  51         (void)implicit_copy;
  52         (void)explicit_copy;
  53         (void)implicit_move;
  54         (void)explicit_move;
  55     }
  56
  57     {
  58         hana::tuple<Trap2> tuple{};
  59         hana::tuple<Trap2> implicit_copy = tuple;
  60         hana::tuple<Trap2> explicit_copy(tuple);
  61         hana::tuple<Trap2> implicit_move = std::move(tuple);
  62         hana::tuple<Trap2> explicit_move(std::move(tuple));
  63
  64         (void)implicit_copy;
  65         (void)explicit_copy;
  66         (void)implicit_move;
  67         (void)explicit_move;
  68     }
  69 }