empty_view.h

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#pragma once
 
#include "di/container/interface/reconstruct.h"
#include "di/container/meta/enable_borrowed_container.h"
#include "di/container/view/view_interface.h"
#include "di/meta/language.h"
#include "di/types/size_t.h"
 
namespace di::container {
template<typename T>
requires(concepts::Object<T>)
class EmptyView
    : public ViewInterface<EmptyView<T>>
    , public meta::EnableBorrowedContainer<EmptyView<T>> {
public:
    constexpr static auto begin() -> T* { return nullptr; }
    constexpr static auto end() -> T* { return nullptr; }
    constexpr static auto data() -> T* { return nullptr; }
    constexpr static auto size() -> types::size_t { return 0; }
    constexpr static auto empty() -> bool { return true; }
 
private:
    constexpr friend auto tag_invoke(types::Tag<container::reconstruct>, InPlaceType<EmptyView>, T*, T*) -> EmptyView {
        return EmptyView {};
    }
    constexpr friend auto tag_invoke(types::Tag<container::reconstruct>, InPlaceType<EmptyView>, nullptr_t, T*)
        -> EmptyView {
        return EmptyView {};
    }
    constexpr friend auto tag_invoke(types::Tag<container::reconstruct>, InPlaceType<EmptyView>, T*, nullptr_t)
        -> EmptyView {
        return EmptyView {};
    }
    constexpr friend auto tag_invoke(types::Tag<container::reconstruct>, InPlaceType<EmptyView>, nullptr_t, nullptr_t)
        -> EmptyView {
        return EmptyView {};
    }
};
}