ceph/src/boost/libs/pfr/test/run/template_unconstrained.cpp

   1 // Copyright (c) 2019-2020 Antony Polukhin
   2 //
   3 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   4 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   5
   6 #include <type_traits>
   7
   8 #include <boost/pfr/core.hpp>
   9
  10 template <class T>
  11 struct unconstrained_template {
  12     unconstrained_template() = default;
  13     unconstrained_template(const unconstrained_template&) = default;
  14     unconstrained_template(unconstrained_template&&) = default;
  15     unconstrained_template& operator=(const unconstrained_template&) = default;
  16     unconstrained_template& operator=(unconstrained_template&&) = default;
  17
  18     template <class U>
  19     constexpr unconstrained_template(const U& val)
  20         : value_{val}
  21     {}
  22
  23     T value_{};
  24 };
  25
  26 struct int_element {
  27     int value_;
  28 };
  29
  30
  31 struct aggregate_unconstrained {
  32     unconstrained_template<int> a;
  33     unconstrained_template<int_element> b;
  34 };
  35
  36 int main() {
  37     using sanity = decltype(aggregate_unconstrained{
  38       boost::pfr::detail::ubiq_lref_constructor{0},
  39       boost::pfr::detail::ubiq_lref_constructor{1},
  40     });
  41     static_assert(
  42         std::is_same<
  43             sanity, aggregate_unconstrained
  44         >::value,
  45         "Precise reflection with template constructors sanity check fails"
  46     );
  47
  48     boost::pfr::detail::enable_if_constructible_helper_t<aggregate_unconstrained, 2> foo;
  49     (void)foo;
  50
  51     static_assert(
  52         std::is_same<
  53             boost::pfr::tuple_element_t<0, aggregate_unconstrained>,
  54             unconstrained_template<int>
  55         >::value,
  56         "Precise reflection with template constructors fails to work"
  57     );
  58
  59     static_assert(
  60         std::is_same<
  61             boost::pfr::tuple_element_t<1, aggregate_unconstrained>,
  62             unconstrained_template<int_element>
  63         >::value,
  64         "Precise reflection with template constructors fails to work"
  65     );
  66
  67     aggregate_unconstrained aggr{3, 4};
  68     return boost::pfr::get<1>(aggr).value_.value_ - 4;
  69 }