dereferenceable.hpp

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//
// Created by cosge on 2023-12-02.
//
 
#ifndef VCCC_CONCEPTS_DEREFERENCEABLE_HPP_
#define VCCC_CONCEPTS_DEREFERENCEABLE_HPP_
 
#include <type_traits>
 
#include "vccc/__type_traits/is_referenceable.hpp"
#include "vccc/__type_traits/void_t.hpp"
 
namespace vccc {
namespace detail {
 
template<typename T, typename = void>
struct dereferenceable_impl_3 : std::false_type {};
 
template<typename T>
struct dereferenceable_impl_3<T, void_t<decltype(*std::declval<T&>())>>
    : is_referencable<decltype(*std::declval<T&>())> {};
 
// Dereferencing a void* is illegal, but some compilers compiles these expression in unevaluated context.
// Omitting dereferenceable_impl_2 does not change the behavior of dereferenceable, but it is to remove warning
template<typename T, bool = std::is_void<std::remove_pointer_t<std::remove_reference_t<T>>>::value /* false */>
struct dereferenceable_impl_2 : dereferenceable_impl_3<T> {};
 
template<typename T>
struct dereferenceable_impl_2<T, true> : std::false_type {};
 
template<typename T, bool = is_referencable<T>::value /* true */>
struct dereferenceable_impl_1 : dereferenceable_impl_2<T> {};
 
template<typename T>
struct dereferenceable_impl_1<T, false> : std::false_type {};
 
} // namespace detail
 
 
 
template<typename T>
struct dereferenceable : detail::dereferenceable_impl_1<T> {};
 
 
} // namespace vccc
 
#endif // VCCC_CONCEPTS_DEREFERENCEABLE_HPP_