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/**
* @file expected.hpp
* @author Felix Morgner (felix.morgner@gmail.com)
* @since 1.0.0
*/
#ifndef WANDA_EXPECTED_HPP
#define WANDA_EXPECTED_HPP
#include <initializer_list>
#include <type_traits>
#include <utility>
namespace wanda
{
/**
* @brief A type to represent the error case of a computation based on #wanda::expected
*/
template<typename ErrorType>
struct unexpected
{
static_assert(!std::is_same_v<ErrorType, void>, "ErrorType can not be 'void'!");
static_assert(!std::is_array_v<ErrorType>, "ErrorType can not be an array type!");
/**
* @brief Copy construct a new @p unexpected from another @p unexpected
*/
constexpr unexpected(unexpected const &) = default;
/**
* @brief Move construct a new @p unexpected from another @p unexpected
*/
constexpr unexpected(unexpected &&) = default;
/**
* @brief Construct a new @p unexpected by direct initializing the error object from @p args
*/
template<typename... Args>
constexpr explicit unexpected(std::in_place_t, Args &&... args)
: m_error(std::forward<Args>(args)...)
{
}
/**
* @brief Construct a new @p unexpected by direct initializing the error object from @p il and @p args
*/
template<
typename U,
typename... Args,
std::enable_if_t<std::is_constructible_v<ErrorType, std::initializer_list<U>, Args...>> * = nullptr>
constexpr explicit unexpected(std::in_place_t, std::initializer_list<U> il, Args &&... args)
: m_error(il, std::forward<Args>(args)...)
{
}
/**
* @brief Construct a new @p unexpected by direct initializing the error object from @p error
*/
template<
typename Err = ErrorType,
std::enable_if_t<std::is_constructible_v<ErrorType, Err> &&
!std::is_same_v<std::remove_cv_t<std::remove_reference_t<Err>>, std::in_place_t> &&
!std::is_same_v<std::remove_cv_t<std::remove_reference_t<Err>>, unexpected>> * = nullptr>
constexpr explicit unexpected(Err && error)
: m_error(std::forward<Err>(error))
{
}
/**
* @brief Construct a new @p unexpected by copying the value of another @p unexpected of different error type
*/
template<
typename Err,
std::enable_if_t<!(
std::is_constructible_v<ErrorType, Err> &&
!std::is_constructible_v<ErrorType, unexpected<Err> &> &&
!std::is_constructible_v<ErrorType, unexpected<Err>> &&
!std::is_constructible_v<ErrorType, unexpected<Err> const &> &&
!std::is_constructible_v<ErrorType, unexpected<Err> const> &&
!std::is_convertible_v<unexpected<Err> &, ErrorType> &&
!std::is_convertible_v<unexpected<Err>, ErrorType> &&
!std::is_convertible_v<unexpected<Err> const &, ErrorType> &&
!std::is_convertible_v<unexpected<Err> const, ErrorType>)> * = nullptr,
std::enable_if_t<!std::is_convertible_v<Err, ErrorType>> * = nullptr>
constexpr explicit unexpected(unexpected<Err> const & error)
: m_error(error.m_error)
{
}
/**
* @brief Construct a new @p unexpected by copying the value of another @p unexpected of different error type
*/
template<
typename Err,
std::enable_if_t<!(
std::is_constructible_v<ErrorType, Err> &&
!std::is_constructible_v<ErrorType, unexpected<Err> &> &&
!std::is_constructible_v<ErrorType, unexpected<Err>> &&
!std::is_constructible_v<ErrorType, unexpected<Err> const &> &&
!std::is_constructible_v<ErrorType, unexpected<Err> const> &&
!std::is_convertible_v<unexpected<Err> &, ErrorType> &&
!std::is_convertible_v<unexpected<Err>, ErrorType> &&
!std::is_convertible_v<unexpected<Err> const &, ErrorType> &&
!std::is_convertible_v<unexpected<Err> const, ErrorType>)> * = nullptr,
std::enable_if_t<std::is_convertible_v<Err, ErrorType>> * = nullptr>
constexpr unexpected(unexpected<Err> const & error)
: m_error(error.m_error)
{
}
/**
* @brief Construct a new @p unexpected by moving the value of another @p unexpected of different error type
*/
template<
typename Err,
std::enable_if_t<!(
std::is_constructible_v<ErrorType, Err> &&
!std::is_constructible_v<ErrorType, unexpected<Err> &> &&
!std::is_constructible_v<ErrorType, unexpected<Err>> &&
!std::is_constructible_v<ErrorType, unexpected<Err> const &> &&
!std::is_constructible_v<ErrorType, unexpected<Err> const> &&
!std::is_convertible_v<unexpected<Err> &, ErrorType> &&
!std::is_convertible_v<unexpected<Err>, ErrorType> &&
!std::is_convertible_v<unexpected<Err> const &, ErrorType> &&
!std::is_convertible_v<unexpected<Err> const, ErrorType>)> * = nullptr,
std::enable_if_t<!std::is_convertible_v<Err, ErrorType>> * = nullptr>
constexpr explicit unexpected(unexpected<Err> && error)
: m_error(std::move(error.m_error))
{
}
/**
* @brief Construct a new @p unexpected by moving the value of another @p unexpected of different error type
*/
template<
typename Err,
std::enable_if_t<!(
std::is_constructible_v<ErrorType, Err> &&
!std::is_constructible_v<ErrorType, unexpected<Err> &> &&
!std::is_constructible_v<ErrorType, unexpected<Err>> &&
!std::is_constructible_v<ErrorType, unexpected<Err> const &> &&
!std::is_constructible_v<ErrorType, unexpected<Err> const> &&
!std::is_convertible_v<unexpected<Err> &, ErrorType> &&
!std::is_convertible_v<unexpected<Err>, ErrorType> &&
!std::is_convertible_v<unexpected<Err> const &, ErrorType> &&
!std::is_convertible_v<unexpected<Err> const, ErrorType>)> * = nullptr,
std::enable_if_t<std::is_convertible_v<Err, ErrorType>> * = nullptr>
constexpr unexpected(unexpected<Err> && error)
: m_error(std::move(error.m_error))
{
}
/**
* @brief Get the error value contained in this @p unexpected instance
*/
constexpr ErrorType const & value() const &
{
return m_error;
}
/**
* @brief Get the error value contained in this @p unexpected instance
*/
constexpr ErrorType & value() &
{
return m_error;
}
/**
* @brief Get the error value contained in this @p unexpected instance
*/
constexpr ErrorType && value() &&
{
return std::move(m_error);
}
/**
* @brief Get the error value contained in this @p unexpected instance
*/
constexpr ErrorType const && value() const &&
{
return std::move(m_error);
}
/**
* @brief Swap the error value of this @p unexpected instance with the one of @p other
*/
void swap(unexpected & other) noexcept(std::is_nothrow_swappable_v<ErrorType>)
{
using std::swap;
swap(m_error, other.m_error);
}
template<typename ErrorType1, typename ErrorType2>
friend constexpr bool operator==(unexpected<ErrorType1> const & lhs, unexpected<ErrorType2> const & rhs);
template<typename ErrorType1, typename ErrorType2>
friend constexpr bool operator!=(unexpected<ErrorType1> const & lhs, unexpected<ErrorType2> const & rhs);
template<
typename Err,
std::enable_if_t<std::is_swappable_v<Err>> *>
friend void swap(unexpected<Err> & lhs, unexpected<Err> & rhs);
private:
ErrorType m_error;
};
template<typename ErrorType>
unexpected(ErrorType)->unexpected<ErrorType>;
/**
* @brief Compare two @p unexpected instances for equality
*/
template<typename ErrorType1, typename ErrorType2>
constexpr bool operator==(unexpected<ErrorType1> const & lhs, unexpected<ErrorType2> const & rhs)
{
return lhs.m_error == rhs.m_error;
}
/**
* @brief Compare two @p unexpected instances for inequality
*/
template<typename ErrorType1, typename ErrorType2>
constexpr bool operator!=(unexpected<ErrorType1> const & lhs, unexpected<ErrorType2> const & rhs)
{
return lhs.m_error != rhs.m_error;
}
/**
* @brief Swap the error values of two @p unexpected instances
*/
template<
typename Err,
std::enable_if_t<std::is_swappable_v<Err>> * = nullptr>
void swap(unexpected<Err> & lhs, unexpected<Err> & rhs)
{
lhs.swap(rhs);
}
/**
* @brief A tag type for @p unexpected
*/
struct unexpect_t
{
explicit unexpect_t() = default;
};
/**
* @brief A tap for @p unexpected
*/
inline constexpr unexpect_t unexpect{};
} // namespace wanda
#endif
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