refactor: replace remaining std::enable_if patterns with C++20 concepts (#7645)

Author: DennisOSRM

include/guidance/turn_data_container.hpp

@@ -78,8 +78,8 @@ template <storage::Ownership Ownership> class TurnDataContainerImpl
     }
 
     // Used by EdgeBasedGraphFactory to fill data structure
-    template <typename = std::enable_if<Ownership == storage::Ownership::Container>>
     void push_back(const TurnData &data)
+        requires(Ownership != storage::Ownership::View)
     {
         turn_instructions.push_back(data.turn_instruction);
         lane_data_ids.push_back(data.lane_data_id);
@@ -88,8 +88,8 @@ template <storage::Ownership Ownership> class TurnDataContainerImpl
         post_turn_bearings.push_back(data.post_turn_bearing);
     }
 
-    template <typename = std::enable_if<Ownership == storage::Ownership::Container>>
     void append(const std::vector<TurnData> &others)
+        requires(Ownership != storage::Ownership::View)
     {
         std::for_each(
             others.begin(), others.end(), [this](const TurnData &other) { push_back(other); });

include/server/api/parameters_parser.hpp

@@ -24,14 +24,14 @@ using is_parameter_t =
 } // namespace detail
 
 // Starts parsing and iter and modifies it until iter == end or parsing failed
-template <typename ParameterT,
-          std::enable_if<detail::is_parameter_t<ParameterT>::value, int>::type = 0>
+template <typename ParameterT>
+    requires detail::is_parameter_t<ParameterT>::value
 std::optional<ParameterT> parseParameters(std::string::iterator &iter,
                                           const std::string::iterator end);
 
 // Copy on purpose because we need mutability
-template <typename ParameterT,
-          std::enable_if<detail::is_parameter_t<ParameterT>::value, int>::type = 0>
+template <typename ParameterT>
+    requires detail::is_parameter_t<ParameterT>::value
 std::optional<ParameterT> parseParameters(std::string options_string)
 {
     auto first = options_string.begin();

include/util/integer_range.hpp

@@ -1,8 +1,8 @@
 #ifndef INTEGER_RANGE_HPP
 #define INTEGER_RANGE_HPP
 
+#include <concepts>
 #include <iterator>
-#include <type_traits>
 
 namespace osrm::util
 {
@@ -105,10 +105,8 @@ template <typename Integer> class range
 };
 
 template <typename Integer>
-range<Integer>
-irange(const Integer first,
-       const Integer last,
-       typename std::enable_if<std::is_integral<Integer>::value>::type * = nullptr) noexcept
+    requires std::integral<Integer>
+range<Integer> irange(const Integer first, const Integer last) noexcept
 {
     return range<Integer>(first, last);
 }

include/util/json_deep_compare.hpp

@@ -6,6 +6,7 @@
 
 #include <boost/assert.hpp>
 
+#include <concepts>
 #include <set>
 
 namespace osrm::util::json
@@ -132,9 +133,8 @@ struct Comparator
         return false;
     }
 
-    template <typename T1,
-              typename T2,
-              typename = std::enable_if<!std::is_same<T1, T2>::value>::type>
+    template <typename T1, typename T2>
+        requires(!std::same_as<T1, T2>)
     bool operator()(const T1 &, const T2 &)
     {
         reason = lhs_path + " and " + rhs_path + " have different types";