refactor: modernise type traits

Core/include/Acts/EventData/TrackStateType.hpp

@@ -14,6 +14,7 @@
 #include <cstdint>
 #include <limits>
 #include <ostream>
+#include <type_traits>
 
 namespace Acts {
 
@@ -38,7 +39,7 @@ class TrackStateType {
  public:
   using raw_type = std::uint64_t;
   static constexpr std::size_t kRawBits =
-      std::numeric_limits<std::make_unsigned<raw_type>::type>::digits;
+      std::numeric_limits<std::make_unsigned_t<raw_type>>::digits;
 
   // Delete default constructor
   TrackStateType() = delete;
@@ -106,7 +107,7 @@ class ConstTrackStateType {
  public:
   using raw_type = std::uint64_t;
   static constexpr std::size_t kRawBits =
-      std::numeric_limits<std::make_unsigned<raw_type>::type>::digits;
+      std::numeric_limits<std::make_unsigned_t<raw_type>>::digits;
 
   // Delete default constructor
   ConstTrackStateType() = delete;

Core/include/Acts/Propagator/Propagator.ipp

@@ -1,6 +1,6 @@
 // This file is part of the Acts project.
 //
-// Copyright (C) 2019 CERN for the benefit of the Acts project
+// Copyright (C) 2019-2024 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
@@ -13,7 +13,7 @@
 #include "Acts/Propagator/StandardAborters.hpp"
 #include "Acts/Propagator/detail/LoopProtection.hpp"
 
-#include <type_traits>
+#include <concepts>
 
 namespace Acts::detail {
 template <typename Stepper, typename StateType, typename N>
@@ -113,9 +113,8 @@ auto Acts::Propagator<S, N>::propagate(const parameters_t& start,
     -> Result<
         actor_list_t_result_t<StepperCurvilinearTrackParameters,
                               typename propagator_options_t::actor_list_type>> {
-  static_assert(
-      std::is_copy_constructible<StepperCurvilinearTrackParameters>::value,
-      "return track parameter type must be copy-constructible");
+  static_assert(std::copy_constructible<StepperCurvilinearTrackParameters>,
+                "return track parameter type must be copy-constructible");
 
   auto state = makeState(start, options);
 
@@ -158,7 +157,7 @@ auto Acts::Propagator<S, N>::makeState(
   // Type of track parameters produced by the propagation
   using ReturnParameterType = StepperCurvilinearTrackParameters;
 
-  static_assert(std::is_copy_constructible<ReturnParameterType>::value,
+  static_assert(std::copy_constructible<ReturnParameterType>,
                 "return track parameter type must be copy-constructible");
 
   // Expand the abort list with a path aborter
@@ -246,7 +245,7 @@ auto Acts::Propagator<S, N>::makeResult(propagator_state_t state,
   // Type of track parameters produced by the propagation
   using ReturnParameterType = StepperCurvilinearTrackParameters;
 
-  static_assert(std::is_copy_constructible<ReturnParameterType>::value,
+  static_assert(std::copy_constructible<ReturnParameterType>,
                 "return track parameter type must be copy-constructible");
 
   // Type of the full propagation result, including output from actors
@@ -291,7 +290,7 @@ auto Acts::Propagator<S, N>::makeResult(
   // Type of track parameters produced at the end of the propagation
   using ReturnParameterType = StepperBoundTrackParameters;
 
-  static_assert(std::is_copy_constructible<ReturnParameterType>::value,
+  static_assert(std::copy_constructible<ReturnParameterType>,
                 "return track parameter type must be copy-constructible");
 
   // Type of the full propagation result, including output from actors

Core/include/Acts/Seeding/detail/CylindricalSpacePointGrid.ipp

@@ -6,6 +6,8 @@
 // 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/.
 
+#include <concepts>
+
 template <typename external_spacepoint_t>
 Acts::CylindricalSpacePointGrid<external_spacepoint_t>
 Acts::CylindricalSpacePointGridCreator::createGrid(
@@ -142,12 +144,12 @@ void Acts::CylindricalSpacePointGridCreator::fillGrid(
     external_spacepoint_iterator_t spBegin,
     external_spacepoint_iterator_t spEnd, Acts::Extent& rRangeSPExtent) {
   using iterated_value_t =
-      typename std::iterator_traits<external_spacepoint_iterator_t>::value_type;
-  using iterated_t = typename std::remove_const<
-      typename std::remove_pointer<iterated_value_t>::type>::type;
-  static_assert(!std::is_pointer<iterated_value_t>::value,
+      typename std::iter_value_t<external_spacepoint_iterator_t>;
+  using iterated_t = typename std::remove_const_t<
+      typename std::remove_pointer_t<iterated_value_t>>;
+  static_assert(!std::is_pointer_v<iterated_value_t>,
                 "Iterator must contain pointers to space points");
-  static_assert(std::is_same<iterated_t, external_spacepoint_t>::value,
+  static_assert(std::same_as<iterated_t, external_spacepoint_t>,
                 "Iterator does not contain type this class was templated with");
 
   if (!config.isInInternalUnits) {

Core/include/Acts/Surfaces/ConvexPolygonBounds.hpp

@@ -16,6 +16,7 @@
 
 #include <array>
 #include <cmath>
+#include <concepts>
 #include <cstddef>
 #include <exception>
 #include <iosfwd>
@@ -54,6 +55,7 @@ class ConvexPolygonBoundsBase : public PlanarBounds {
   /// @param vertices A collection of vertices.
   /// throws a logic error if this is not the case
   template <typename coll_t>
+    requires std::same_as<typename coll_t::value_type, Acts::Vector2>
   static void convex_impl(const coll_t& vertices) noexcept(false);
 };
 

Core/include/Acts/Surfaces/ConvexPolygonBounds.ipp

@@ -10,14 +10,13 @@
 #include "Acts/Surfaces/detail/BoundaryCheckHelper.hpp"
 #include "Acts/Utilities/ThrowAssert.hpp"
 
+#include <concepts>
 #include <optional>
 
 template <typename coll_t>
+  requires std::same_as<typename coll_t::value_type, Acts::Vector2>
 void Acts::ConvexPolygonBoundsBase::convex_impl(
     const coll_t& vertices) noexcept(false) {
-  static_assert(std::is_same<typename coll_t::value_type, Vector2>::value,
-                "Must be collection of Vector2");
-
   const std::size_t N = vertices.size();
   for (std::size_t i = 0; i < N; i++) {
     std::size_t j = (i + 1) % N;

Core/include/Acts/TrackFinding/CombinatorialKalmanFilter.hpp

@@ -44,6 +44,7 @@
 #include <functional>
 #include <limits>
 #include <memory>
+#include <ranges>
 #include <string_view>
 #include <type_traits>
 #include <unordered_map>
@@ -357,10 +358,7 @@ class CombinatorialKalmanFilter {
       const auto& [boundParams, jacobian, pathLength] = boundState;
 
       trackStateCandidates.clear();
-      if constexpr (std::is_same_v<
-                        typename std::iterator_traits<
-                            source_link_iterator_t>::iterator_category,
-                        std::random_access_iterator_tag>) {
+      if constexpr (std::ranges::random_access_range<source_link_iterator_t>) {
         trackStateCandidates.reserve(std::distance(slBegin, slEnd));
       }
 

Core/include/Acts/TrackFitting/GlobalChiSquareFitter.hpp

@@ -45,6 +45,7 @@
 #include <limits>
 #include <map>
 #include <memory>
+#include <type_traits>
 #include <unordered_map>
 
 namespace Acts::Experimental {
@@ -513,7 +514,7 @@ class Gx2Fitter {
 
   /// The navigator has DirectNavigator type or not
   static constexpr bool isDirectNavigator =
-      std::is_same<Gx2fNavigator, DirectNavigator>::value;
+      std::is_same_v<Gx2fNavigator, DirectNavigator>;
 
  public:
   Gx2Fitter(propagator_t pPropagator,

Core/include/Acts/TrackFitting/KalmanFitter.hpp

@@ -37,6 +37,7 @@
 #include <limits>
 #include <map>
 #include <memory>
+#include <type_traits>
 
 namespace Acts {
 
@@ -264,7 +265,7 @@ class KalmanFitter {
 
   /// The navigator has DirectNavigator type or not
   static constexpr bool isDirectNavigator =
-      std::is_same<KalmanNavigator, DirectNavigator>::value;
+      std::is_same_v<KalmanNavigator, DirectNavigator>;
 
  public:
   KalmanFitter(propagator_t pPropagator,

Core/include/Acts/Utilities/Concepts.hpp

@@ -20,8 +20,7 @@ concept same_as_any_of = (std::same_as<T, Ts> || ...);
 /// @brief Concept that is equivalent to `is_nothrow_move_constructible`.
 /// @todo Convert this to a "real" concept.
 template <typename T>
-concept nothrow_move_constructible =
-    std::is_nothrow_move_constructible<T>::value;
+concept nothrow_move_constructible = std::is_nothrow_move_constructible_v<T>;
 
 /// @brief Concept that is true if T is an arithmetic type.
 template <typename T>

Core/include/Acts/Utilities/FiniteStateMachine.hpp

@@ -119,8 +119,7 @@ class FiniteStateMachine {
   /// Default constructor. The default state is taken to be the first in the
   /// `States` template arguments
   FiniteStateMachine()
-      : m_state(typename std::tuple_element<0, std::tuple<States...>>::type{}) {
-  }
+      : m_state(typename std::tuple_element_t<0, std::tuple<States...>>{}) {}
 
   /// Constructor from an explicit state. The FSM is initialized to this state.
   /// @param state Initial state for the FSM.

Core/include/Acts/Utilities/GridBinFinder.ipp

@@ -6,20 +6,21 @@
 // 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/.
 
+#include <type_traits>
+
 template <std::size_t DIM>
 template <typename first_value_t, typename... vals>
 void Acts::GridBinFinder<DIM>::storeValue(first_value_t&& fv,
                                           vals&&... others) {
   constexpr std::size_t N = sizeof...(vals);
   static_assert(N < DIM);
   /// Check the fist value is reasonable
-  using decayed_value_t = typename std::decay<first_value_t>::type;
-  if constexpr (std::is_same<int, decayed_value_t>::value) {
+  using decayed_value_t = typename std::decay_t<first_value_t>;
+  if constexpr (std::is_same_v<int, decayed_value_t>) {
     /// if int -> value is positive
     assert(fv >= 0);
     m_values[DIM - N - 1ul] = fv;
-  } else if constexpr (std::is_same<std::pair<int, int>,
-                                    decayed_value_t>::value) {
+  } else if constexpr (std::is_same_v<std::pair<int, int>, decayed_value_t>) {
     m_values[DIM - N - 1ul] = fv;
   } else {
     /// If vector of pairs -> also allow for empty vectors
@@ -41,12 +42,11 @@ std::array<std::pair<int, int>, DIM> Acts::GridBinFinder<DIM>::getSizePerAxis(
   for (std::size_t i(0ul); i < DIM; ++i) {
     output[i] = std::visit(
         [&locPosition, i](const auto& val) -> std::pair<int, int> {
-          using value_t = typename std::decay<decltype(val)>::type;
-          if constexpr (std::is_same<int, value_t>::value) {
+          using value_t = typename std::decay_t<decltype(val)>;
+          if constexpr (std::is_same_v<int, value_t>) {
             assert(val >= 0);
             return std::make_pair(-val, val);
-          } else if constexpr (std::is_same<std::pair<int, int>,
-                                            value_t>::value) {
+          } else if constexpr (std::is_same_v<std::pair<int, int>, value_t>) {
             return std::make_pair(-val.first, val.second);
           } else {
             assert(locPosition.size() > i);
@@ -82,9 +82,9 @@ bool Acts::GridBinFinder<DIM>::isGridCompatible(
     std::size_t nBins = nLocBins[i];
     bool isCompabile = std::visit(
         [nBins](const auto& val) -> bool {
-          using value_t = typename std::decay<decltype(val)>::type;
-          if constexpr (std::is_same<int, value_t>::value ||
-                        std::is_same<std::pair<int, int>, value_t>::value) {
+          using value_t = typename std::decay_t<decltype(val)>;
+          if constexpr (std::is_same_v<int, value_t> ||
+                        std::is_same_v<std::pair<int, int>, value_t>) {
             return true;
           } else {
             return val.size() == nBins;

Core/include/Acts/Utilities/TransformRange.hpp

@@ -148,8 +148,7 @@ struct TransformRange {
 template <typename Callable, typename iterator_t, bool force_const>
 struct TransformRangeIterator {
  private:
-  using internal_value_type =
-      typename std::iterator_traits<iterator_t>::value_type;
+  using internal_value_type = typename std::iter_value_t<iterator_t>;
 
   using raw_value_type = std::remove_reference_t<decltype(Callable::apply(
       std::declval<internal_value_type>()))>;
@@ -162,8 +161,7 @@ struct TransformRangeIterator {
       std::conditional_t<force_const, std::add_const_t<raw_value_type>,
                          raw_value_type>;
 
-  using difference_type =
-      typename std::iterator_traits<iterator_t>::difference_type;
+  using difference_type = typename std::iter_difference_t<iterator_t>;
   using pointer = std::remove_reference_t<value_type>*;
   using reference = value_type&;
   using iterator_category = std::forward_iterator_tag;

Core/include/Acts/Utilities/detail/interpolation_impl.hpp

@@ -46,14 +46,14 @@ struct can_interpolate {
   static std::false_type point_type_test(...);
 
   static const bool value =
-      std::is_same<std::true_type,
-                   decltype(value_type_test<Value>(nullptr))>::value &&
-      std::is_same<std::true_type,
-                   decltype(point_type_test<Point1>(nullptr))>::value &&
-      std::is_same<std::true_type,
-                   decltype(point_type_test<Point2>(nullptr))>::value &&
-      std::is_same<std::true_type,
-                   decltype(point_type_test<Point3>(nullptr))>::value;
+      std::is_same_v<std::true_type,
+                     decltype(value_type_test<Value>(nullptr))> &&
+      std::is_same_v<std::true_type,
+                     decltype(point_type_test<Point1>(nullptr))> &&
+      std::is_same_v<std::true_type,
+                     decltype(point_type_test<Point2>(nullptr))> &&
+      std::is_same_v<std::true_type,
+                     decltype(point_type_test<Point3>(nullptr))>;
 };
 
 /// @brief concept equivalent to `can_interpolate`

Examples/Io/Csv/include/ActsExamples/Io/Csv/CsvInputOutput.hpp

@@ -273,9 +273,8 @@ class NamedTupleDsvWriter {
 
   /// Append a record to the file.
   void append(const NamedTuple& record) {
-    append_impl(record,
-                std::make_index_sequence<
-                    std::tuple_size<typename NamedTuple::Tuple>::value>{});
+    append_impl(record, std::make_index_sequence<
+                            std::tuple_size_v<typename NamedTuple::Tuple>>{});
   }
 
  private:
@@ -548,8 +547,7 @@ inline bool NamedTupleDsvReader<Delimiter, NamedTuple>::read(
                              std::to_string(m_reader.num_lines()));
   }
   // convert to tuple
-  parse_record(record,
-               std::make_index_sequence<std::tuple_size<Tuple>::value>{});
+  parse_record(record, std::make_index_sequence<std::tuple_size_v<Tuple>>{});
   return true;
 }
 
@@ -572,7 +570,7 @@ inline bool NamedTupleDsvReader<Delimiter, NamedTuple>::read(
 template <char Delimiter, typename NamedTuple>
 inline void NamedTupleDsvReader<Delimiter, NamedTuple>::use_default_columns() {
   // assume row content is identical in content and order to the tuple
-  m_num_columns = std::tuple_size<Tuple>::value;
+  m_num_columns = std::tuple_size_v<Tuple>;
   for (std::size_t i = 0; i < m_tuple_column_map.size(); ++i) {
     m_tuple_column_map[i] = i;
   }

Plugins/Json/include/Acts/Plugins/Json/GeometryHierarchyMapJsonConverter.hpp

@@ -155,7 +155,7 @@ nlohmann::json GeometryHierarchyMapJsonConverter<value_t, decorator_t>::toJson(
   for (std::size_t i = 0; i < container.size(); ++i) {
     auto entry = encodeIdentifier(container.idAt(i));
     auto value_json = nlohmann::json(container.valueAt(i));
-    if constexpr (!std::is_same<decorator_t, void>::value) {
+    if constexpr (!std::is_same_v<decorator_t, void>) {
       decorateJson(decorator, container.valueAt(i), value_json);
     }
     entry["value"] = std::move(value_json);

Tests/UnitTests/Core/EventData/TrackStatePropMaskTests.cpp

@@ -49,7 +49,7 @@ BOOST_AUTO_TEST_CASE(BitmaskOperators) {
   BOOST_CHECK(!ACTS_CHECK_BIT(bs4, PM::Filtered));
 
   auto cnv = [](auto a) -> std::bitset<8> {
-    return static_cast<std::underlying_type<PM>::type>(a);
+    return static_cast<std::underlying_type_t<PM>>(a);
   };
 
   BOOST_CHECK(cnv(PM::All).all());    // all ones

Tests/UnitTests/Core/Utilities/ExtendableTests.cpp

@@ -33,7 +33,7 @@ BOOST_AUTO_TEST_CASE(Extendable_) {
   // Test the empty list
   detail::Extendable<> nullist{};
   (void)nullist;
-  BOOST_CHECK_EQUAL(std::tuple_size<std::tuple<>>::value, 0u);
+  BOOST_CHECK_EQUAL(std::tuple_size_v<std::tuple<>>, 0u);
 
   detail::Extendable<TypeA> alist;
   auto& a0_object = alist.get<TypeA>();

Tests/UnitTests/Core/Utilities/GridTests.cpp

@@ -17,11 +17,11 @@
 
 #include <algorithm>
 #include <array>
+#include <concepts>
 #include <cstddef>
 #include <set>
 #include <string>
 #include <tuple>
-#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -1308,10 +1308,10 @@ BOOST_AUTO_TEST_CASE(grid_type_conversion) {
   Grid g2(Type<double>, std::move(a), std::move(b));
   decltype(g2) g2Copy(g2.axesTuple());
 
-  static_assert(std::is_same<decltype(g2), decltype(g2Copy)>::value);
+  static_assert(std::same_as<decltype(g2), decltype(g2Copy)>);
 
   auto g2ConvertedInt = g2Copy.convertType<int>();
-  static_assert(std::is_same<decltype(g2ConvertedInt), Grid2Int>::value);
+  static_assert(std::same_as<decltype(g2ConvertedInt), Grid2Int>);
 }
 
 BOOST_AUTO_TEST_CASE(grid_full_conversion) {