Log if we've double-assigned an exit

MomentaryMeeting/Game/ArrangementGenerator.cs

@@ -174,8 +174,17 @@
                 _logger.LogWarning($"Unknown location {locationB} encountered in links");
                 return; // abort
             }
-            if (canGoAToB) locations[locationA].SetNeighbour(dirAToB, locationB);
-            if (canGoBToA) locations[locationB].SetNeighbour(dirBToA, locationA);
+            if (canGoAToB)
+            {
+                if (!string.IsNullOrEmpty(locations[locationA].GetNeighbour(dirAToB))) _logger.LogWarning($"Overwriting link {locationA} {dirAToB} ({locations[locationA].GetNeighbour(dirAToB)}->{locationB})");
+                locations[locationA].SetNeighbour(dirAToB, locationB);
+            }
+
+            if (canGoBToA)
+            {
+                if (!string.IsNullOrEmpty(locations[locationB].GetNeighbour(dirBToA))) _logger.LogWarning($"Overwriting link {locationB} {dirBToA} ({locations[locationB].GetNeighbour(dirBToA)}->{locationA})");
+                locations[locationB].SetNeighbour(dirBToA, locationA);
+            }
         }
 
         // Generate a new concrete arrangement of locations