roundabout for segregated entry roads

src/extractor/guidance/intersection_generator.cpp

@@ -208,6 +208,15 @@ Intersection IntersectionGenerator::mergeSegregatedRoads(Intersection intersecti
     if (intersection.size() == 1)
         return intersection;
 
+    const bool is_connected_to_roundabout = [this,&intersection]() {
+        for (const auto &road : intersection)
+        {
+            if (node_based_graph.GetEdgeData(road.turn.eid).roundabout)
+                return true;
+        }
+        return false;
+    }();
+
     // check for merges including the basic u-turn
     // these result in an adjustment of all other angles
     if (mergable(0, intersection.size() - 1))
@@ -216,8 +225,24 @@ Intersection IntersectionGenerator::mergeSegregatedRoads(Intersection intersecti
             (360 - intersection[intersection.size() - 1].turn.angle) / 2;
         for (std::size_t i = 1; i + 1 < intersection.size(); ++i)
             intersection[i].turn.angle += correction_factor;
+
+        // FIXME if we have a left-sided country, we need to switch this off and enable it below
         intersection[0] = merge(intersection.front(), intersection.back());
         intersection[0].turn.angle = 0;
+
+        if (is_connected_to_roundabout)
+        {
+            // We are merging a u-turn against the direction of a roundabout
+            //
+            //    -----------> roundabout
+            //       /    \
+            //    out      in
+            //
+            // These cases have to be disabled, even if they are not forbidden specifically by a
+            // relation
+            intersection[0].entry_allowed = false;
+        }
+
         intersection.pop_back();
     }