Codechange: simplify the type of loaded_at_xy / next_station (#11182)

It was TileOrStationID, most likely to make sure both types in
the union are identical. But as TileIndex is a StrongTypeDef
that becomes a bit weird. So instead, still make sure they are
of equal size, but define their individual types better.

(cherry picked from commit c9c9cfa4fd)

src/cargopacket.cpp

@@ -745,7 +745,7 @@ void VehicleCargoList::InvalidateCache()
  * @return Amount of cargo actually reassigned.
  */
 template<VehicleCargoList::MoveToAction Tfrom, VehicleCargoList::MoveToAction Tto>
-uint VehicleCargoList::Reassign(uint max_move, TileOrStationID)
+uint VehicleCargoList::Reassign(uint max_move, StationID)
 {
 	static_assert(Tfrom != MTA_TRANSFER && Tto != MTA_TRANSFER);
 	static_assert(Tfrom - Tto == 1 || Tto - Tfrom == 1);
@@ -763,7 +763,7 @@ uint VehicleCargoList::Reassign(uint max_move, TileOrStationID)
  * @return Amount of cargo actually reassigned.
  */
 template<>
-uint VehicleCargoList::Reassign<VehicleCargoList::MTA_DELIVER, VehicleCargoList::MTA_TRANSFER>(uint max_move, TileOrStationID next_station)
+uint VehicleCargoList::Reassign<VehicleCargoList::MTA_DELIVER, VehicleCargoList::MTA_TRANSFER>(uint max_move, StationID next_station)
 {
 	max_move = std::min(this->action_counts[MTA_DELIVER], max_move);
 
@@ -1161,4 +1161,4 @@ uint StationCargoList::RerouteFromSource(uint max_move, StationCargoList *dest,
  */
 template class CargoList<VehicleCargoList, CargoPacketList>;
 template class CargoList<StationCargoList, StationCargoPacketMap>;
-template uint VehicleCargoList::Reassign<VehicleCargoList::MTA_DELIVER, VehicleCargoList::MTA_KEEP>(uint, TileOrStationID);
+template uint VehicleCargoList::Reassign<VehicleCargoList::MTA_DELIVER, VehicleCargoList::MTA_KEEP>(uint, StationID);

src/cargopacket.h

@@ -43,11 +43,16 @@ namespace upstream_sl {
 	class SlStationGoods;
 }
 
-typedef uint32 TileOrStationID;
-
 void ClearCargoPacketDeferredPayments();
 void ChangeOwnershipOfCargoPacketDeferredPayments(Owner old_owner, Owner new_owner);
 
+/**
+ * To make alignment in the union in CargoPacket a bit easier, create a new type
+ * that is a StationID, but stored as 32bit.
+ */
+typedef uint32_t StationID_32bit;
+static_assert(sizeof(TileIndex) == sizeof(StationID_32bit));
+
 /**
  * Container for cargo from the same location and time.
  */
@@ -59,8 +64,8 @@ private:
 	SourceID source_id;     ///< Index of source, INVALID_SOURCE if unknown/invalid.
 	TileIndex source_xy;    ///< The origin of the cargo (first station in feeder chain).
 	union {
-		TileOrStationID loaded_at_xy; ///< Location where this cargo has been loaded into the vehicle.
-		TileOrStationID next_station; ///< Station where the cargo wants to go next.
+		TileIndex loaded_at_xy;       ///< Location where this cargo has been loaded into the vehicle.
+		StationID_32bit next_station; ///< Station where the cargo wants to go next.
 	};
 	StationID source;       ///< The station where the cargo came from first.
 	SourceType source_type; ///< Type of \c source_id.
@@ -467,7 +472,7 @@ public:
 	 * applicable), return value is amount of cargo actually moved. */
 
 	template<MoveToAction Tfrom, MoveToAction Tto>
-	uint Reassign(uint max_move, TileOrStationID update = INVALID_TILE);
+	uint Reassign(uint max_move, StationID update = INVALID_STATION);
 	uint Return(uint max_move, StationCargoList *dest, StationID next_station);
 	uint Unload(uint max_move, StationCargoList *dest, CargoPayment *payment);
 	uint Shift(uint max_move, VehicleCargoList *dest);