Replace boost::optional with std::optional (#6611)

src/extractor/intersection/node_based_graph_walker.cpp

@@ -66,7 +66,7 @@ SelectRoadByNameOnlyChoiceAndStraightness::SelectRoadByNameOnlyChoiceAndStraight
 {
 }
 
-boost::optional<EdgeID> SelectRoadByNameOnlyChoiceAndStraightness::operator()(
+std::optional<EdgeID> SelectRoadByNameOnlyChoiceAndStraightness::operator()(
     const NodeID /*nid*/,
     const EdgeID /*via_edge_id*/,
     const IntersectionView &intersection,
@@ -118,7 +118,7 @@ SelectStraightmostRoadByNameAndOnlyChoice::SelectStraightmostRoadByNameAndOnlyCh
 {
 }
 
-boost::optional<EdgeID> SelectStraightmostRoadByNameAndOnlyChoice::operator()(
+std::optional<EdgeID> SelectStraightmostRoadByNameAndOnlyChoice::operator()(
     const NodeID /*nid*/,
     const EdgeID /*via_edge_id*/,
     const IntersectionView &intersection,
@@ -241,7 +241,7 @@ boost::optional<EdgeID> SelectStraightmostRoadByNameAndOnlyChoice::operator()(
             return {};
     }
 
-    return is_only_choice_with_same_name ? boost::optional<EdgeID>(min_element->eid) : boost::none;
+    return is_only_choice_with_same_name ? std::optional<EdgeID>(min_element->eid) : std::nullopt;
 }
 
 // ---------------------------------------------------------------------------------

src/extractor/maneuver_override_relation_parser.cpp

@@ -1,9 +1,9 @@
 #include "extractor/maneuver_override_relation_parser.hpp"
 #include "extractor/maneuver_override.hpp"
 
-#include <boost/optional/optional.hpp>
 #include <boost/ref.hpp>
 
+#include <optional>
 #include <osmium/osm.hpp>
 #include <osmium/tags/filter.hpp>
 #include <osmium/tags/taglist.hpp>
@@ -21,7 +21,7 @@ ManeuverOverrideRelationParser::ManeuverOverrideRelationParser() {}
  * into an InputManeuverOverride object, if the relation is considered
  * valid (i.e. has the minimum tags we expect).
  */
-boost::optional<InputManeuverOverride>
+std::optional<InputManeuverOverride>
 ManeuverOverrideRelationParser::TryParse(const osmium::Relation &relation) const
 {
 
@@ -35,7 +35,7 @@ ManeuverOverrideRelationParser::TryParse(const osmium::Relation &relation) const
     if (osmium::tags::match_none_of(tag_list, filter))
     // if it's not a maneuver, continue;
     {
-        return boost::none;
+        return std::nullopt;
     }
 
     // we pretend every restriction is a conditional restriction. If we do not find any restriction,
@@ -130,7 +130,7 @@ ManeuverOverrideRelationParser::TryParse(const osmium::Relation &relation) const
     }
     else
     {
-        return boost::none;
+        return std::nullopt;
     }
     return maneuver_override;
 }