add a toolkit function to find lanes to the left/right of turn lanes

src/engine/guidance/lane_processing.cpp

@@ -4,7 +4,7 @@
 
 #include "extractor/guidance/turn_instruction.hpp"
 #include "engine/guidance/post_processing.hpp"
-#include "engine/guidance/toolkit.hpp"
+#include "extractor/guidance/toolkit.hpp"
 
 #include <iterator>
 #include <unordered_set>
@@ -16,6 +16,8 @@ namespace DirectionModifier = osrm::extractor::guidance::DirectionModifier;
 
 using osrm::util::guidance::isLeftTurn;
 using osrm::util::guidance::isRightTurn;
+using osrm::extractor::guidance::numLanesToTheRight;
+using osrm::extractor::guidance::numLanesToTheLeft;
 
 namespace osrm
 {
@@ -80,12 +82,8 @@ std::vector<RouteStep> anticipateLaneChange(std::vector<RouteStep> steps,
             // where lanes in the turn fan in but for example the overall lanes at that location
             // fan out, we would have to know the asymmetric mapping of lanes. This is currently
             // not possible at the moment. In the following we implement a heuristic instead.
-            const LaneID current_num_all_lanes =
-                current.intersections.front().lane_description.size();
-            const LaneID current_num_lanes_right_of_turn = current_lanes.first_lane_from_the_right;
-            const LaneID current_num_lanes_left_of_turn =
-                current_num_all_lanes -
-                (current_lanes.lanes_in_turn + current_num_lanes_right_of_turn);
+            const LaneID current_num_lanes_right_of_turn = numLanesToTheRight(current);
+            const LaneID current_num_lanes_left_of_turn = numLanesToTheLeft(current);
 
             const LaneID num_shared_lanes = std::min(current_lanes.lanes_in_turn,   //
                                                      previous_lanes.lanes_in_turn); //