abort_condition_signature_check.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 2016-2018 CERN for the benefit of the Acts project
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#pragma once

#include <type_traits>
#include "Acts/Utilities/TypeTraits.hpp"
#include "Acts/Utilities/detail/MPL/type_collector.hpp"

namespace Acts {


namespace concept {
  namespace detail_aborter {

  template <typename A, typename propagator_state_t, typename stepper_t>
  using call_op_no_result_t = decltype(std::declval<const A>()(
      std::declval<propagator_state_t&>(), std::declval<const stepper_t&>()));

  template <typename A, typename result_t, typename propagator_state_t,
            typename stepper_t>
  using call_op_with_result_t = decltype(std::declval<const A>()(
      std::declval<propagator_state_t&>(), std::declval<const stepper_t&>(),
      std::declval<const result_t&>()));

  // This is basically an if:
  // if ( !Aborter.hasResult() ) { // has no result
  template <typename T, typename propagator_state_t, typename stepper_t,
            bool has_result = false>
  struct ConceptConditional {
    // check the existence of the correct call operator
    constexpr static bool value =
        Acts::concept ::exists<call_op_no_result_t, T, propagator_state_t,
                               stepper_t>;
  };

  // } else { // has a result
  template <typename T, typename propagator_state_t, typename stepper_t>
  struct ConceptConditional<T, propagator_state_t, stepper_t, true> {
    // unpack the result type from the action contained in the aborter type
    using result_type =
        Acts::detail::result_type_t<Acts::detail::action_type_t<T>>;
    // check the existence of the correct call operator
    constexpr static bool value =
        Acts::concept ::exists<call_op_with_result_t, T, result_type,
                               propagator_state_t, stepper_t>;
  };
  // } // endif

  // Calls the 'if' above, depending on the value of `has_action_type_v`.
  template <typename T, typename propagator_state_t, typename stepper_t>
  struct Concept {
    constexpr static bool value =
        ConceptConditional<T, propagator_state_t, stepper_t,
                           Acts::detail::has_action_type_v<T>>::value;
  };

  }  // namespace detail_aborter

  template <typename T, typename propagator_state_t, typename stepper_t>
  constexpr bool abort_condition_signature_check_v =
      detail_aborter::Concept<T, propagator_state_t, stepper_t>::value;
}  // namespace concept
}  // namespace Acts