#define TILE_DISALLOW_SLOPES(name, errtext, next) \
switch (FEAT_INDUSTRYTILES, SELF, THIS_ID(name), \
( \
nearby_tile_height(-1 * relative_x, -1 * relative_y) \
+ (nearby_tile_slope(-1 * relative_x, -1 * relative_y) \
== SLOPE_FLAT ? 0 : \
nearby_tile_slope(-1 * relative_x, -1 * relative_y) == bitmask(IS_STEEP_SLOPE) ? 2 : 1 \
)) == (nearby_tile_height(0, 0) \
+ (nearby_tile_slope(0, 0) \
== SLOPE_FLAT ? 0 : \
nearby_tile_slope(0, 0) == bitmask(IS_STEEP_SLOPE) ? 2 : 1)) \
) { \
1: next; \
return errtext; \
}