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

   1 // Copyright (c) 2019-2022 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 constrained_template {
  12     constrained_template() = default;
  13
  14     template <
  15       class U = T,
  16       std::enable_if_t<
  17           std::is_constructible<T, U&&>::value
  18           || sizeof(decltype(T{std::declval<U&&>()}))
  19       , bool> = false>
  20     constexpr constrained_template(U&& val)
  21         : value_{std::forward<U>(val)}
  22     {}
  23
  24     T value_;
  25 };
  26
  27 struct int_element {
  28     int value_;
  29 };
  30
  31 struct aggregate_constrained {
  32     constrained_template<short> a;
  33     constrained_template<int_element> b;
  34 };
  35
  36 int main() {
  37     static_assert(
  38         std::is_same<
  39             boost::pfr::tuple_element_t<0, aggregate_constrained>,
  40             constrained_template<short>
  41         >::value,
  42         "Precise reflection with template constructors fails to work"
  43     );
  44
  45     static_assert(
  46         std::is_same<
  47             boost::pfr::tuple_element_t<1, aggregate_constrained>,
  48             constrained_template<int_element>
  49         >::value,
  50         "Precise reflection with template constructors fails to work"
  51     );
  52
  53     short s = 3;
  54     aggregate_constrained aggr{s, 4};
  55     return boost::pfr::get<1>(aggr).value_.value_ - 4;
  56 }