Show specific reason why vehicle cannot be ordered to a particular station

src/lang/english.txt

@@ -6413,6 +6413,19 @@ STR_ERROR_CAN_T_COPY_ORDER_LIST                                 :{WHITE}Can't co
 STR_ERROR_TOO_FAR_FROM_PREVIOUS_DESTINATION                     :{WHITE}... too far from previous destination
 STR_ERROR_AIRCRAFT_NOT_ENOUGH_RANGE                             :{WHITE}... aircraft has not enough range
 
+STR_ERROR_NO_RAIL_STATION                                       :{WHITE}There is no railway station...
+STR_ERROR_NO_BUS_STATION                                        :{WHITE}There is no bus station...
+STR_ERROR_NO_TRUCK_STATION                                      :{WHITE}There is no lorry station...
+STR_ERROR_NO_DOCK                                               :{WHITE}There is no dock...
+STR_ERROR_NO_AIRPORT                                            :{WHITE}There is no airport/heliport...
+STR_ERROR_NO_STOP_COMPATIBLE_ROAD_TYPE                          :{WHITE}There are no stops with a compatible road/tram type...
+STR_ERROR_NO_STOP_ARTIC_VEH                                     :{WHITE}There are no stops which are suitable for articulated road vehicles.{}Articulated road vehicles require a drive-through stop, not a bay stop...
+STR_ERROR_AIRPORT_NO_PLANES                                     :{WHITE}This plane cannot land at this heliport...
+STR_ERROR_AIRPORT_NO_HELIS                                      :{WHITE}This helicopter cannot land at this airport...
+STR_ERROR_NO_RAIL_WAYPOINT                                      :{WHITE}There is no railway waypoint...
+STR_ERROR_NO_ROAD_WAYPOINT                                      :{WHITE}There is no road waypoint...
+STR_ERROR_NO_BUOY                                               :{WHITE}There is no buoy...
+
 # Timetable related errors
 STR_ERROR_CAN_T_TIMETABLE_VEHICLE                               :{WHITE}Can't timetable vehicle...
 STR_ERROR_TIMETABLE_ONLY_WAIT_AT_STATIONS                       :{WHITE}Vehicles can only wait at stations

src/order_cmd.cpp

@@ -984,9 +984,9 @@ CommandCost CmdInsertOrderIntl(DoCommandFlag flags, Vehicle *v, VehicleOrderID s
 				if (ret.Failed()) return ret;
 			}
 
-			if (!CanVehicleUseStation(v, st)) return_cmd_error(STR_ERROR_CAN_T_ADD_ORDER);
+			if (!CanVehicleUseStation(v, st)) return CommandCost::DualErrorMessage(STR_ERROR_CAN_T_ADD_ORDER, GetVehicleCannotUseStationReason(v, st));
 			for (Vehicle *u = v->FirstShared(); u != nullptr; u = u->NextShared()) {
-				if (!CanVehicleUseStation(u, st)) return_cmd_error(STR_ERROR_CAN_T_ADD_ORDER_SHARED);
+				if (!CanVehicleUseStation(u, st)) return CommandCost::DualErrorMessage(STR_ERROR_CAN_T_ADD_ORDER_SHARED, GetVehicleCannotUseStationReason(u, st));
 			}
 
 			/* Non stop only allowed for ground vehicles. */
@@ -1083,7 +1083,7 @@ CommandCost CmdInsertOrderIntl(DoCommandFlag flags, Vehicle *v, VehicleOrderID s
 				default: return CMD_ERROR;
 
 				case VEH_TRAIN: {
-					if (!(wp->facilities & FACIL_TRAIN)) return_cmd_error(STR_ERROR_CAN_T_ADD_ORDER);
+					if (!(wp->facilities & FACIL_TRAIN)) return CommandCost::DualErrorMessage(STR_ERROR_CAN_T_ADD_ORDER, STR_ERROR_NO_RAIL_WAYPOINT);
 
 					CommandCost ret = CheckInfraUsageAllowed(v->type, wp->owner);
 					if (ret.Failed()) return ret;
@@ -1091,7 +1091,7 @@ CommandCost CmdInsertOrderIntl(DoCommandFlag flags, Vehicle *v, VehicleOrderID s
 				}
 
 				case VEH_ROAD: {
-					if (!(wp->facilities & FACIL_BUS_STOP) || !(wp->facilities & FACIL_TRUCK_STOP)) return_cmd_error(STR_ERROR_CAN_T_ADD_ORDER);
+					if (!(wp->facilities & FACIL_BUS_STOP) || !(wp->facilities & FACIL_TRUCK_STOP)) return CommandCost::DualErrorMessage(STR_ERROR_CAN_T_ADD_ORDER, STR_ERROR_NO_ROAD_WAYPOINT);
 
 					CommandCost ret = CheckInfraUsageAllowed(v->type, wp->owner);
 					if (ret.Failed()) return ret;
@@ -1099,7 +1099,7 @@ CommandCost CmdInsertOrderIntl(DoCommandFlag flags, Vehicle *v, VehicleOrderID s
 				}
 
 				case VEH_SHIP:
-					if (!(wp->facilities & FACIL_DOCK)) return_cmd_error(STR_ERROR_CAN_T_ADD_ORDER);
+					if (!(wp->facilities & FACIL_DOCK)) return CommandCost::DualErrorMessage(STR_ERROR_CAN_T_ADD_ORDER, STR_ERROR_NO_BUOY);
 					if (wp->owner != OWNER_NONE) {
 						CommandCost ret = CheckInfraUsageAllowed(v->type, wp->owner);
 						if (ret.Failed()) return ret;

src/vehicle.cpp

@@ -4338,6 +4338,55 @@ bool CanVehicleUseStation(const Vehicle *v, const Station *st)
 	return CanVehicleUseStation(v->engine_type, st);
 }
 
+/**
+ * Get reason string why this station can't be used by the given vehicle
+ * @param v the vehicle to test
+ * @param st the station to test for
+ * @return true if and only if the vehicle can use this station.
+ */
+StringID GetVehicleCannotUseStationReason(const Vehicle *v, const Station *st)
+{
+	switch (v->type) {
+		case VEH_TRAIN:
+			return STR_ERROR_NO_RAIL_STATION;
+
+		case VEH_ROAD: {
+			const RoadVehicle *rv = RoadVehicle::From(v);
+			RoadStop *rs = st->GetPrimaryRoadStop(rv->IsBus() ? ROADSTOP_BUS : ROADSTOP_TRUCK);
+
+			StringID err = rv->IsBus() ? STR_ERROR_NO_BUS_STATION : STR_ERROR_NO_TRUCK_STATION;
+
+			for (; rs != nullptr; rs = rs->next) {
+				/* The vehicle is articulated and can therefore not go to a standard road stop. */
+				if (IsStandardRoadStopTile(rs->xy) && rv->HasArticulatedPart()) {
+					err = STR_ERROR_NO_STOP_ARTIC_VEH;
+					continue;
+				}
+				/* The vehicle cannot go to this roadstop (different roadtype) */
+				if (!HasTileAnyRoadType(rs->xy, rv->compatible_roadtypes)) return STR_ERROR_NO_STOP_COMPATIBLE_ROAD_TYPE;
+
+				return INVALID_STRING_ID;
+			}
+
+			return err;
+		}
+
+		case VEH_SHIP:
+			return STR_ERROR_NO_DOCK;
+
+		case VEH_AIRCRAFT:
+			if ((st->facilities & FACIL_AIRPORT) == 0) return STR_ERROR_NO_AIRPORT;
+			if (v->GetEngine()->u.air.subtype & AIR_CTOL) {
+				return STR_ERROR_AIRPORT_NO_PLANES;
+			} else {
+				return STR_ERROR_AIRPORT_NO_HELIS;
+			}
+
+		default:
+			return INVALID_STRING_ID;
+	}
+}
+
 /**
  * Access the ground vehicle cache of the vehicle.
  * @pre The vehicle is a #GroundVehicle.

src/vehicle_func.h

@@ -248,6 +248,7 @@ extern uint16 _returned_mail_refit_capacity;
 
 bool CanVehicleUseStation(EngineID engine_type, const struct Station *st);
 bool CanVehicleUseStation(const Vehicle *v, const struct Station *st);
+StringID GetVehicleCannotUseStationReason(const Vehicle *v, const Station *st);
 
 void ReleaseDisastersTargetingVehicle(VehicleID vehicle);