type_traits_impl.hpp

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#pragma once
 
#include <yaclib/fwd.hpp>
 
#include <type_traits>
 
namespace yaclib::detail {
 
template <typename...>
struct Head;
 
template <typename T, typename... Args>
struct Head<T, Args...> final {
  using Type = T;
};
 
template <typename Func, typename... Args>
struct IsInvocable final {
  static constexpr bool Value = std::is_invocable_v<Func, Args...>;
};
 
template <typename Func>
struct IsInvocable<Func, void> final {
  static constexpr bool Value = std::is_invocable_v<Func>;
};
 
template <typename Func, typename... Args>
struct Invoke final {
  using Type = std::invoke_result_t<Func, Args...>;
};
 
template <typename Func>
struct Invoke<Func, void> final {
  using Type = std::invoke_result_t<Func>;
};
 
template <template <typename...> typename Instance, typename...>
struct IsInstantiationOf final {
  static constexpr bool Value = false;
};
 
template <template <typename...> typename Instance, typename... Args>
struct IsInstantiationOf<Instance, Instance<Args...>> final {
  static constexpr bool Value = true;
};
 
template <template <typename...> typename Instance, typename T>
struct InstantiationTypes final {
  using Value = T;
  using Error = T;
};
 
template <template <typename...> typename Instance, typename V, typename E>
struct InstantiationTypes<Instance, Instance<V, E>> final {
  using Value = V;
  using Error = E;
};
 
template <typename T>
struct FutureBaseTypes final {
  using Value = T;
  using Error = T;
};
 
template <typename V, typename E>
struct FutureBaseTypes<FutureBase<V, E>> final {
  using Value = V;
  using Error = E;
};
 
template <typename V, typename E>
struct FutureBaseTypes<Future<V, E>> final {
  using Value = V;
  using Error = E;
};
 
template <typename V, typename E>
struct FutureBaseTypes<FutureOn<V, E>> final {
  using Value = V;
  using Error = E;
};
 
}  // namespace yaclib::detail