is_empty.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2019 Tobias Hienzsch
 
#ifndef TETL_TYPE_TRAITS_IS_EMPTY_HPP
#define TETL_TYPE_TRAITS_IS_EMPTY_HPP
 
#include <etl/_type_traits/bool_constant.hpp>
#include <etl/_type_traits/is_class.hpp>
#include <etl/_type_traits/remove_cv.hpp>
 
namespace etl {
 
namespace detail {
 
template <typename T>
struct is_empty_tester_1 : etl::remove_cv_t<T> {
    char dummy_data;
};
 
struct is_empty_tester_2 {
    char dummy_data;
};
 
template <typename T>
struct is_empty : false_type { };
 
template <typename T>
    requires is_class_v<T>
struct is_empty<T> : bool_constant<sizeof(is_empty_tester_1<T>) == sizeof(is_empty_tester_2)> { };
 
} // namespace detail
 
/// \brief f T is an empty type (that is, a non-union class type with no
/// non-static data members other than bit-fields of size 0, no virtual
/// functions, no virtual base classes, and no non-empty base classes), provides
/// the member constant value equal to true. For any other type, value is false.
template <typename T>
struct is_empty : detail::is_empty<T> { };
 
template <typename T>
inline constexpr bool is_empty_v = is_empty<T>::value;
 
} // namespace etl
 
#endif // TETL_TYPE_TRAITS_IS_EMPTY_HPP