concepts.hh

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/* ========================================================================== *
 *
 * @file compat/concepts.hh
 *
 * @brief Provides backports of some `concepts` features that are missing in
 *        Clang v11.
 *
 *
 * -------------------------------------------------------------------------- */
 
#pragma once
 
#include <concepts>  // IWYU pragma: export
 
 
/* -------------------------------------------------------------------------- */
 
/* Only provide these definitions for older versions of Clang. */
#if defined( __clang__ ) && ( __clang_major__ < 15 )
 
/* -------------------------------------------------------------------------- */
 
/* Yeah, I know: "iT's IlLeGaL tO eXtEnD `std::*'".
 * This backports definitions exactly as written, so it's fine. */
namespace std {
 
/* -------------------------------------------------------------------------- */
 
template<class T>
concept destructible = std::is_nothrow_destructible_v<T>;
 
 
/* -------------------------------------------------------------------------- */
 
template<class T, class... Args>
concept constructible_from
  = std::destructible<T> && std::is_constructible_v<T, Args...>;
 
 
/* -------------------------------------------------------------------------- */
 
template<class From, class To>
concept convertible_to = std::is_convertible_v<From, To> && requires {
  static_cast<To>( std::declval<From>() );
};
 
 
/* -------------------------------------------------------------------------- */
 
template<class Derived, class Base>
concept derived_from
  = std::is_base_of_v<Base, Derived>
    && std::is_convertible_v<const volatile Derived *, const volatile Base *>;
 
 
/* -------------------------------------------------------------------------- */
 
}  // namespace std
 
 
/* -------------------------------------------------------------------------- */
 
#endif  // defined( __clang__ ) && ( __clang_major__ < 15 )
 
 
/* -------------------------------------------------------------------------- *
 *
 *
 *
 * ========================================================================== */