optional_storage.h

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#pragma once
 
#include "di/meta/core.h"
#include "di/meta/operations.h"
#include "di/util/as_const.h"
#include "di/util/forward.h"
#include "di/util/move.h"
#include "di/vocab/optional/get_value.h"
#include "di/vocab/optional/is_nullopt.h"
#include "di/vocab/optional/nullopt.h"
#include "di/vocab/optional/set_nullopt.h"
#include "di/vocab/optional/set_value.h"
 
namespace di::vocab {
template<typename Storage, typename T>
concept OptionalStorage = requires(Storage& storage, T&& value) {
    { is_nullopt(util::as_const(storage)) } -> concepts::SameAs<bool>;
    { set_nullopt(storage) };
    { get_value(storage) };
    { get_value(util::as_const(storage)) };
    { get_value(util::move(storage)) };
    { get_value(util::move(util::as_const(storage))) };
} && concepts::ConstructibleFrom<Storage, NullOpt>;
}