Add misc debug flag for water flooding states

src/console_cmds.cpp

@@ -2855,6 +2855,7 @@ DEF_CONSOLE_CMD(ConMiscDebug)
 	if (argc < 1 || argc > 2) {
 		IConsoleHelp("Debug: misc flags.  Usage: 'misc_debug [<flags>]'");
 		IConsoleHelp("  1: MDF_OVERHEAT_BREAKDOWN_OPEN_WIN");
+		IConsoleHelp("  2: MDF_ZONING_RS_WATER_FLOOD_STATE");
 		return true;
 	}
 

src/debug_settings.h

@@ -25,6 +25,7 @@ inline bool HasChickenBit(ChickenBitFlags flag)
 
 enum MiscDebugFlags {
 	MDF_OVERHEAT_BREAKDOWN_OPEN_WIN,
+	MDF_ZONING_RS_WATER_FLOOD_STATE,
 };
 extern uint32 _misc_debug_flags;
 

src/zoning_cmd.cpp

@@ -26,6 +26,7 @@
 #include "zoning.h"
 #include "viewport_func.h"
 #include "road_map.h"
+#include "debug_settings.h"
 #include "3rdparty/cpp-btree/btree_set.h"
 
 Zoning _zoning;
@@ -252,6 +253,9 @@ SpriteID TileZoneCheckTraceRestrictEvaluation(TileIndex tile, Owner owner)
 	if (IsTileType(tile, MP_RAILWAY) && HasSignals(tile) && IsRestrictedSignal(tile)) {
 		return SPR_ZONING_INNER_HIGHLIGHT_RED;
 	}
+	if (unlikely(HasBit(_misc_debug_flags, MDF_ZONING_RS_WATER_FLOOD_STATE)) && IsNonFloodingWaterTile(tile)) {
+		return SPR_ZONING_INNER_HIGHLIGHT_YELLOW;
+	}
 
 	return ZONING_INVALID_SPRITE_ID;
 }