EQ2EMu/EQ2/source/depends/boost_1_72_0/libs/outcome/test/tests/issue0203.cpp

/* Unit testing for outcomes
(C) 2013-2019 Niall Douglas <http://www.nedproductions.biz/> (1 commit)


Boost Software License - Version 1.0 - August 17th, 2003

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*/

#include <boost/outcome/std_result.hpp>
#include <boost/outcome/try.hpp>
#include <boost/test/unit_test.hpp>
#include <boost/test/unit_test_monitor.hpp>

namespace outcome = BOOST_OUTCOME_V2_NAMESPACE;

enum class error
{
  test,
  abcde
};

class error_category_impl : public std::error_category
{
public:
  const char *name() const noexcept override { return "test"; }

  std::string message(int code) const noexcept override
  {
    switch(static_cast<error>(code))
    {
    case error::test:
      return "test";
    case error::abcde:
      return "abcde";
    }
    return "unknown";
  }
};
const std::error_category &error_category() noexcept
{
  static error_category_impl instance;
  return instance;
}

boost::system::error_code make_error_code(error error) noexcept
{
  return {static_cast<int>(error), error_category()};
}

namespace std
{
  template <> struct is_error_code_enum<error> : true_type
  {
  };
}  // namespace std

template <typename T> using enum_result = outcome::basic_result<T, error, outcome::policy::default_policy<T, error, void>>;

enum_result<int> test()
{
  return 5;
}

outcome::std_result<int> abc()
{
  static_assert(std::is_error_code_enum<error>::value, "custom enum is not marked convertible to error code");
  static_assert(std::is_constructible<boost::system::error_code, error>::value, "error code is not explicitly constructible from custom enum");
  static_assert(std::is_convertible<error, boost::system::error_code>::value, "error code is not implicitly constructible from custom enum");
  boost::system::error_code ec = error::test;  // custom enum is definitely convertible to error code
  BOOST_OUTCOME_TRY(test());               // hence this should compile, as implicit conversions work here
  (void) ec;

  // But explicit conversions are required between dissimilar basic_result, implicit conversions are disabled
  static_assert(std::is_constructible<outcome::std_result<int>, enum_result<int>>::value, "basic_result with error code is not explicitly constructible from basic_result with custom enum");
  static_assert(!std::is_convertible<enum_result<int>, outcome::std_result<int>>::value, "basic_result with error code is implicitly constructible from basic_result with custom enum");
  return 5;
}

BOOST_OUTCOME_AUTO_TEST_CASE(issues_0203_test, "enum convertible to error code works as designed")
{
  BOOST_CHECK(abc().value() == 5);
}