Fix #6875: Depot building cost does not include foundation build cost (#6883)

bin/ai/regression/tst_regression/result.txt

@@ -7253,7 +7253,7 @@ ERROR: IsEnd() is invalid as Begin() is never called
   IsBuoyTile():         false
   IsLockTile():         false
   IsCanalTile():        false
-  GetBankBalance():     479851
+  GetBankBalance():     479664
   BuildWaterDepot():    true
   BuildDock():          true
   BuildBuoy():          true
@@ -7266,7 +7266,7 @@ ERROR: IsEnd() is invalid as Begin() is never called
   IsBuoyTile():         true
   IsLockTile():         true
   IsCanalTile():        true
-  GetBankBalance():     465257
+  GetBankBalance():     465070
 
 --AIWaypointList(BUOY)--
   Count():             1
@@ -7285,7 +7285,7 @@ ERROR: IsEnd() is invalid as Begin() is never called
   IsBuoyTile():         false
   IsLockTile():         false
   IsCanalTile():        false
-  GetBankBalance():     459862
+  GetBankBalance():     459675
   BuildWaterDepot():    true
   BuildDock():          true
 

src/rail_cmd.cpp

@@ -967,6 +967,8 @@ CommandCost CmdBuildTrainDepot(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 
 	DiagDirection dir = Extract<DiagDirection, 0, 2>(p2);
 
+	CommandCost cost(EXPENSES_CONSTRUCTION);
+
 	/* Prohibit construction if
 	 * The tile is non-flat AND
 	 * 1) build-on-slopes is disabled
@@ -974,14 +976,14 @@ CommandCost CmdBuildTrainDepot(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 	 * 3) the exit points in the wrong direction
 	 */
 
-	if (tileh != SLOPE_FLAT && (
-				!_settings_game.construction.build_on_slopes ||
-				!CanBuildDepotByTileh(dir, tileh)
-			)) {
-		return_cmd_error(STR_ERROR_FLAT_LAND_REQUIRED);
+	if (tileh != SLOPE_FLAT) {
+		if (!_settings_game.construction.build_on_slopes || !CanBuildDepotByTileh(dir, tileh)) {
+			return_cmd_error(STR_ERROR_FLAT_LAND_REQUIRED);
+		}
+		cost.AddCost(_price[PR_BUILD_FOUNDATION]);
 	}
 
-	CommandCost cost = DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
+	cost.AddCost(DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR));
 	if (cost.Failed()) return cost;
 
 	if (IsBridgeAbove(tile)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);

src/road_cmd.cpp

@@ -1017,15 +1017,17 @@ CommandCost CmdBuildRoadDepot(TileIndex tile, DoCommandFlag flags, uint32 p1, ui
 
 	if (!IsValidRoadType(rt) || !ValParamRoadType(rt)) return CMD_ERROR;
 
+	CommandCost cost(EXPENSES_CONSTRUCTION);
+
 	Slope tileh = GetTileSlope(tile);
-	if (tileh != SLOPE_FLAT && (
-				!_settings_game.construction.build_on_slopes ||
-				!CanBuildDepotByTileh(dir, tileh)
-			)) {
-		return_cmd_error(STR_ERROR_FLAT_LAND_REQUIRED);
+	if (tileh != SLOPE_FLAT) {
+		if (!_settings_game.construction.build_on_slopes || !CanBuildDepotByTileh(dir, tileh)) {
+			return_cmd_error(STR_ERROR_FLAT_LAND_REQUIRED);
+		}
+		cost.AddCost(_price[PR_BUILD_FOUNDATION]);
 	}
 
-	CommandCost cost = DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
+	cost.AddCost(DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR));
 	if (cost.Failed()) return cost;
 
 	if (IsBridgeAbove(tile)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);