ceph/src/boost/libs/hana/test/map/cnstr.default.cpp

   1 // Copyright Louis Dionne 2013-2017
   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/bool.hpp>
   6 #include <boost/hana/fwd/hash.hpp>
   7 #include <boost/hana/map.hpp>
   8 #include <boost/hana/pair.hpp>
   9 #include <boost/hana/type.hpp>
  10
  11 #include <type_traits>
  12 namespace hana = boost::hana;
  13
  14
  15 struct NoDefault {
  16     NoDefault() = delete;
  17     NoDefault(NoDefault const&) = default;
  18     constexpr explicit NoDefault(int) { }
  19 };
  20
  21 auto operator==(NoDefault const&, NoDefault const&) { return hana::true_c; }
  22 auto operator!=(NoDefault const&, NoDefault const&) { return hana::false_c; }
  23
  24 // Note: It is also useful to check with a non-empty class, because that
  25 //       triggers different instantiations due to EBO.
  26 struct NoDefault_nonempty {
  27     NoDefault_nonempty() = delete;
  28     NoDefault_nonempty(NoDefault_nonempty const&) = default;
  29     constexpr explicit NoDefault_nonempty(int k) : i(k) { }
  30     int i;
  31 };
  32
  33 auto operator==(NoDefault_nonempty const&, NoDefault_nonempty const&) { return hana::true_c; }
  34 auto operator!=(NoDefault_nonempty const&, NoDefault_nonempty const&) { return hana::false_c; }
  35
  36 struct Default {
  37     Default() = default;
  38     Default(Default const&) = default;
  39     constexpr explicit Default(int) { }
  40 };
  41
  42 auto operator==(Default const&, Default const&) { return hana::true_c; }
  43 auto operator!=(Default const&, Default const&) { return hana::false_c; }
  44
  45 namespace boost { namespace hana {
  46     template <>
  47     struct hash_impl<NoDefault> {
  48         static constexpr auto apply(NoDefault const&)
  49         { return hana::type_c<NoDefault>; };
  50     };
  51
  52     template <>
  53     struct hash_impl<NoDefault_nonempty> {
  54         static constexpr auto apply(NoDefault_nonempty const&)
  55         { return hana::type_c<NoDefault_nonempty>; };
  56     };
  57
  58     template <>
  59     struct hash_impl<Default> {
  60         static constexpr auto apply(Default const&)
  61         { return hana::type_c<Default>; };
  62     };
  63 }}
  64
  65 int main() {
  66     auto map1 = hana::make_map(hana::make_pair(Default(1), Default(1)));
  67     static_assert(std::is_default_constructible<decltype(map1)>::value, "");
  68
  69     auto map2 = hana::make_map(hana::make_pair(NoDefault(1), NoDefault(1)));
  70     static_assert(!std::is_default_constructible<decltype(map2)>::value, "");
  71
  72     auto map3 = hana::make_map(hana::make_pair(NoDefault_nonempty(1), NoDefault_nonempty(1)));
  73     static_assert(!std::is_default_constructible<decltype(map3)>::value, "");
  74 }