#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; \
}