outcome/test/tests/issue0244.cpp

/* Unit testing for outcomes
(C) 2013-2026 Niall Douglas <http://www.nedproductions.biz/> (1 commit)


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

Permission is hereby granted, free of charge, to any person or organization
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*/

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

namespace issues244
{
  namespace outcome = BOOST_OUTCOME_V2_NAMESPACE;

  static int counter = 0;
  static std::vector<int> default_constructor, copy_constructor, move_constructor, destructor;
  struct Foo
  {
    int x{2};
    explicit Foo(int v)
        : x(v)
    {
      std::cout << "   Default constructor " << ++counter << std::endl;
      default_constructor.push_back(counter);
    }
    Foo(const Foo &o) noexcept
        : x(o.x)
    {
      std::cout << "   Copy constructor " << ++counter << std::endl;
      copy_constructor.push_back(counter);
    }
    Foo(Foo &&o) noexcept
        : x(o.x)
    {
      std::cout << "   Move constructor " << ++counter << std::endl;
      move_constructor.push_back(counter);
    }
    ~Foo()
    {
      std::cout << "   Destructor " << ++counter << std::endl;
      destructor.push_back(counter);
    }
  };
  struct Immovable
  {
    int x{2};
    explicit Immovable(int v)
        : x(v)
    {
    }
      Immovable(const Immovable &) = delete;
    Immovable(Immovable &&) = delete;
  };

  outcome::result<Foo> get_foo() noexcept { return outcome::result<Foo>(outcome::in_place_type<Foo>, 5); }

  template <typename T> T &&filterR(T &&v) { return static_cast<T &&>(v); }
  template <typename T> const T &filterL(T &&v) { return v; }
}  // namespace issues244


BOOST_OUTCOME_AUTO_TEST_CASE(issues_0244_test, "TRY/TRYX has dangling reference if xvalues are emitted from tried expression")
{
  using namespace issues244;
  auto check = [](const char *desc, auto &&f) {
    counter = 0;
    default_constructor.clear();
    copy_constructor.clear();
    move_constructor.clear();
    destructor.clear();
    std::cout << "\n" << desc << std::endl;
    auto r = f();
    std::cout << "   Check integer " << ++counter << std::endl;
    BOOST_REQUIRE(r);
    BOOST_CHECK(r.value() == 5);
    if(!copy_constructor.empty())
    {
      BOOST_CHECK(copy_constructor.front() < destructor.front());
    }
    else if(!move_constructor.empty())
    {
      BOOST_CHECK(move_constructor.front() < destructor.front());
    }
  };

  /*
   Default constructor 1    (bind expression prvalue to unique rvalue)
   Move constructor 2       (move from unique rvalue to v value)
   After TRY 3
   Destructor 4             (destruct v value)
   Destructor 5             (destruct lifetime extended unique rvalue)
   Check integer 6
  */
  check("prvalue from expression with lifetime extension is moved into value", []() -> outcome::result<int> {
    BOOST_OUTCOME_TRY(auto v, get_foo());
    std::cout << "   After TRY " << ++counter << std::endl;
    return v.x;
  });
  /*
   Default constructor 1    (bind expression prvalue to unique rvalue)
                            (bind unique rvalue to v rvalue)
   After TRY 2
   Destructor 3             (destruct lifetime extended unique rvalue)
   Check integer 4
  */
  check("prvalue from expression with lifetime extension is bound into rvalue", []() -> outcome::result<int> {
    BOOST_OUTCOME_TRY(auto &&v, get_foo());
    std::cout << "   After TRY " << ++counter << std::endl;
    return v.x;
  });

  /*
   Default constructor 1
   Move constructor 2       (move expression xvalue into unique value)
   Destructor 3             (destruct expression xvalue)
   Move constructor 4       (move from unique value to v value)
   After TRY 5
   Destructor 6             (destruct v value)
   Destructor 7             (destruct unique value)
   Check integer 8
  */
  check("xvalue from expression without lifetime extension is moved into temporary and then moved into value", []() -> outcome::result<int> {
    BOOST_OUTCOME_TRY(auto v, filterR(get_foo()));
    std::cout << "   After TRY " << ++counter << std::endl;
    return v.x;
  });
  /*
   Default constructor 1
   Move constructor 2       (move expression xvalue into unique value)
   Destructor 3             (destruct expression xvalue)
   After TRY 4
   Destructor 5             (destruct unique value)
   Check integer 6
  */
  check("xvalue from expression without lifetime extension is moved into temporary and then bound into rvalue", []() -> outcome::result<int> {
    BOOST_OUTCOME_TRY(auto &&v, filterR(get_foo()));
    std::cout << "   After TRY " << ++counter << std::endl;
    return v.x;
  });

  /*
   Default constructor 1
   Copy constructor 2       (copy expression lvalue into unique value)
   Destructor 3             (destruct expression lvalue)
   Copy constructor 4       (copy from unique value to v value)
   After TRY 5
   Destructor 6             (destruct v value)
   Destructor 7             (destruct unique value)
   Check integer 8
  */
  check("lvalue from expression without lifetime extension is moved into temporary and then moved into value", []() -> outcome::result<int> {
    BOOST_OUTCOME_TRY(auto v, filterL(get_foo()));
    std::cout << "   After TRY " << ++counter << std::endl;
    return v.x;
  });
  /*
   Default constructor 1
   Copy constructor 2       (copy expression lvalue into unique value)
   Destructor 3             (destruct expression lvalue)
   After TRY 4
   Destructor 5             (destruct unique value)
   Check integer 6
  */
  check("lvalue from expression without lifetime extension is moved into temporary and then bound into rvalue", []() -> outcome::result<int> {
    BOOST_OUTCOME_TRY(auto &&v, filterL(get_foo()));
    std::cout << "   After TRY " << ++counter << std::endl;
    return v.x;
  });


  check("TRY lvalue passthrough", []() -> outcome::result<int> {
    const auto &x = outcome::result<Immovable>(outcome::in_place_type<Immovable>, 5);
    // Normally a lvalue input triggers value unique, which would fail to compile here
    BOOST_OUTCOME_TRY((auto &, v), x);
    return v.x;
  });

  // Force use of rvalue refs for unique and bound value
  check("TRY rvalue passthrough", []() -> outcome::result<int> {
    auto &&x = outcome::result<Immovable>(outcome::in_place_type<Immovable>, 5);
    // Normally an xvalue input triggers value unique, which would fail to compile here
    BOOST_OUTCOME_TRY((auto &&, v), x);
    return v.x;
  });

  // Force use of lvalue refs for unique and bound value
  check("TRY prvalue as lvalue passthrough", []() -> outcome::result<int> {
    outcome::result<Immovable> i(outcome::in_place_type<Immovable>, 5);
    BOOST_OUTCOME_TRY((auto &, v), i);
    return v.x;
  });

  // Force use of rvalue refs for unique and bound value
  check("TRY prvalue as rvalue passthrough", []() -> outcome::result<int> {
    outcome::result<Immovable> i(outcome::in_place_type<Immovable>, 5);
    BOOST_OUTCOME_TRY((auto &&, v), i);
    return v.x;
  });


  check("TRYV lvalue passthrough", []() -> outcome::result<int> {
    const auto &x = outcome::result<Immovable>(outcome::in_place_type<Immovable>, 5);
    // Normally a lvalue input triggers value unique, which would fail to compile here
    BOOST_OUTCOME_TRYV2(auto &, x);
    return 5;
  });

  // Force use of rvalue refs for unique and bound value
  check("TRYV rvalue passthrough", []() -> outcome::result<int> {
    auto &&x = outcome::result<Immovable>(outcome::in_place_type<Immovable>, 5);
    // Normally an xvalue input triggers value unique, which would fail to compile here
    BOOST_OUTCOME_TRYV2(auto &&, x);
    return 5;
  });

  // Force use of lvalue refs for unique and bound value
  check("TRYV prvalue as lvalue passthrough", []() -> outcome::result<int> {
    outcome::result<Immovable> i(outcome::in_place_type<Immovable>, 5);
    BOOST_OUTCOME_TRYV2(auto &, i);
    return 5;
  });

  // Force use of rvalue refs for unique and bound value
  check("TRYV prvalue as rvalue passthrough", []() -> outcome::result<int> {
    outcome::result<Immovable> i(outcome::in_place_type<Immovable>, 5);
    BOOST_OUTCOME_TRYV2(auto &, i);
    return 5;
  });
}