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#pragma once
#include <concepts>
#include <utility>
namespace NYT {
////////////////////////////////////////////////////////////////////////////////
//! Default implementation of wrapper traits you can specialize for your type
template <class T>
requires std::is_object_v<T>
struct TBasicWrapperTraits
{
static constexpr bool IsTrivialWrapper = true;
using TUnwrapped = T;
//! Default implementations just forward the argument
template <class U>
requires std::same_as<std::remove_cvref_t<U>, T>
static constexpr decltype(auto) Unwrap(U&& wrapper) noexcept;
static constexpr bool HasValue(const T& wrapper) noexcept;
};
////////////////////////////////////////////////////////////////////////////////
//! Represents common denominator of every single value wrapper
template <class T>
requires std::is_object_v<T>
struct TWrapperTraits
{
public:
static constexpr bool IsTrivialWrapper = TBasicWrapperTraits<T>::IsTrivialWrapper;
using TWrapped = T;
using TUnwrapped = typename TBasicWrapperTraits<T>::TUnwrapped;
static constexpr bool HasValue(const T& wrapper) noexcept;
static constexpr bool RecursiveHasValue(const T& wrapper) noexcept;
template <class U>
requires std::same_as<std::remove_cvref_t<U>, T>
static constexpr decltype(auto) Unwrap(U&& wrapper);
template <class U>
requires std::same_as<std::remove_cvref_t<U>, T>
static constexpr decltype(auto) RecursiveUnwrap(U&& wrapper);
using TRecursiveUnwrapped = std::remove_cvref_t<decltype(TWrapperTraits<T>::RecursiveUnwrap(std::declval<T>()))>;
//! Unfortunatelly, clang is incapable of processing associated constraints if they depend
//! on class information (e.g. aliases and static varibles) and written out-of-line.
//! TODO(arkady-e1ppa): Add proper constraints when clang supports them:
//! Wrap: std::same_as<std::remove_cvref_t<U>, TUnwrapped>
//! RecursiveWrap: std::same_as<std::remove_cvref_t<U>, TRecursiveUnwrapped>
//! Proper constructible_from checks? Easy for wrap, hard for recursive wrap.
template <class U>
static constexpr T Wrap(U&& unwrapped) noexcept;
template <class U>
static constexpr T RecursiveWrap(U&& unwrapped) noexcept;
};
////////////////////////////////////////////////////////////////////////////////
template <class T>
concept CNonTrivialWrapper =
(!TBasicWrapperTraits<T>::IsTrivialWrapper) &&
requires (T& wrapper, const T& const_wrapper) {
typename TBasicWrapperTraits<T>::TUnwrapped;
{ TBasicWrapperTraits<T>::Unwrap(wrapper) } -> std::same_as<typename TBasicWrapperTraits<T>::TUnwrapped&>;
{ TBasicWrapperTraits<T>::Unwrap(std::move(wrapper)) } -> std::same_as<typename TBasicWrapperTraits<T>::TUnwrapped&&>;
{ TBasicWrapperTraits<T>::Unwrap(const_wrapper) } -> std::same_as<const typename TBasicWrapperTraits<T>::TUnwrapped&>;
{ TBasicWrapperTraits<T>::HasValue(const_wrapper) } -> std::same_as<bool>;
};
////////////////////////////////////////////////////////////////////////////////
} // namespace NYT
#define WRAPPER_TRAITS_INL_H_
#include "wrapper_traits-inl.h"
#undef WRAPPER_TRAITS_INL_H_
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