update source to Ceph Pacific 16.2.2

[ceph.git] / ceph / src / boost / libs / outcome / test / tests / constexpr.cpp

/* Unit testing for outcomes
(C) 2013-2020 Niall Douglas <http://www.nedproductions.biz/> (9 commits)


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

Permission is hereby granted, free of charge, to any person or organization
obtaining a copy of the software and accompanying documentation covered by
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FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
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*/

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

#if __cplusplus >= 201700 || _HAS_CXX17
// Match LiteralType, even on C++ 17 and later
template <class T> struct is_literal_type
{
  static constexpr bool value =   //
  std::is_void<T>::value          //
  || std::is_scalar<T>::value     //
  || std::is_reference<T>::value  //
  // leave out is_array for simplicity
  || (std::is_class<T>::value && std::is_trivially_destructible<T>::value
      // how does one detect if a type has at least one constexpr constructor without Reflection???
      )  // leave out union for simplicity
  ;
};
#else
template <class T> using is_literal_type = std::is_literal_type<T>;
#endif

BOOST_OUTCOME_AUTO_TEST_CASE(works_outcome_constexpr, "Tests that outcome works as intended in a constexpr evaluation context")
{
  using namespace BOOST_OUTCOME_V2_NAMESPACE;

  static_assert(is_literal_type<result<int, void, void>>::value, "result<int, void, void> is not a literal type!");
  static_assert(is_literal_type<outcome<int, void, void>>::value, "outcome<int, void, void> is not a literal type!");

  // Unfortunately result<T> can never be a literal type as error_code can never be literal
  //
  // It can however be trivially destructible as error_code is trivially destructible. That
  // makes possible lots of compiler optimisations
  static_assert(std::is_trivially_destructible<result<int>>::value, "result<int> is not trivially destructible!");
  static_assert(std::is_trivially_destructible<result<void>>::value, "result<void> is not trivially destructible!");

  // outcome<T> default has no trivial operations, but if configured it can become so
  static_assert(std::is_trivially_destructible<outcome<int, boost::system::error_code, void>>::value,
                "outcome<int, boost::system::error_code, void> is not trivially destructible!");

  {
    // Test compatible results can be constructed from one another
    constexpr result<int, long> g(in_place_type<int>, 5);
    constexpr result<long, int> g2(g);
    static_assert(g.has_value(), "");
    static_assert(!g.has_error(), "");
    static_assert(g.assume_value() == 5, "");  // value() with UDT E won't compile
    static_assert(g2.has_value(), "");
    static_assert(!g2.has_error(), "");
    static_assert(g2.assume_value() == 5, "");  // value() with UDT E won't compile
    constexpr result<void, int> g3(in_place_type<void>);
    constexpr result<long, int> g4(g3);
    constexpr result<int, void> g5(in_place_type<void>);
    constexpr result<long, int> g6(g5);
    (void) g4;
    (void) g6;

    // Test void
    constexpr result<void, int> h(in_place_type<void>);
    static_assert(h.has_value(), "");
    constexpr result<int, void> h2(in_place_type<void>);
    static_assert(!h2.has_value(), "");
    static_assert(h2.has_error(), "");

    // Test const
    constexpr result<const int, void> i(5);
    constexpr result<const int, void> i2(i);
    (void) i2;
  }
  {
    // Test compatible outcomes can be constructed from one another
    constexpr outcome<int, long, char *> g(in_place_type<int>, 5);
    constexpr outcome<long, int, const char *> g2(g);
    static_assert(g.has_value(), "");
    static_assert(!g.has_error(), "");
    static_assert(!g.has_exception(), "");
    static_assert(g.assume_value() == 5, "");  // value() with UDT E won't compile
    static_assert(g2.has_value(), "");
    static_assert(!g2.has_error(), "");
    static_assert(!g2.has_exception(), "");
    static_assert(g2.assume_value() == 5, "");  // value() with UDT E won't compile
    constexpr outcome<void, int, char *> g3(in_place_type<void>);
    constexpr outcome<long, int, const char *> g4(g3);
    constexpr outcome<int, void, char *> g5(in_place_type<void>);
    constexpr outcome<long, int, const char *> g6(g5);
    (void) g4;
    (void) g6;
  }
}