Program: 164297
Project: 164297
Buggy source:
@Override protected void decorate(){
  for (  Room room : rooms) {
    if (room.type != Room.Type.STANDARD) {
      continue;
    }
    if (room.width() <= 3 || room.height() <= 3) {
      continue;
    }
    int s=room.square();
    if (Random.Int(s) > 8) {
      int corner=(room.left + 1) + (room.top + 1) * WIDTH;
      if (map[corner - 1] == Terrain.WALL && map[corner - WIDTH] == Terrain.WALL) {
        map[corner]=Terrain.WALL;
      }
    }
    if (Random.Int(s) > 8) {
      int corner=(room.right - 1) + (room.top + 1) * WIDTH;
      if (map[corner + 1] == Terrain.WALL && map[corner - WIDTH] == Terrain.WALL) {
        map[corner]=Terrain.WALL;
      }
    }
    if (Random.Int(s) > 8) {
      int corner=(room.left + 1) + (room.bottom - 1) * WIDTH;
      if (map[corner - 1] == Terrain.WALL && map[corner + WIDTH] == Terrain.WALL) {
        map[corner]=Terrain.WALL;
      }
    }
    if (Random.Int(s) > 8) {
      int corner=(room.right - 1) + (room.bottom - 1) * WIDTH;
      if (map[corner + 1] == Terrain.WALL && map[corner + WIDTH] == Terrain.WALL) {
        map[corner]=Terrain.WALL;
      }
    }
    for (    Room n : room.connected.keySet()) {
      if ((n.type == Room.Type.STANDARD || n.type == Room.Type.TUNNEL) && Random.Int(3) == 0) {
        Painter.set(this,room.connected.get(n),Terrain.EMPTY_DECO);
      }
    }
  }
  for (int i=WIDTH + 1; i < LENGTH - WIDTH; i++) {
    if (map[i] == Terrain.EMPTY) {
      int n=0;
      if (map[i + 1] == Terrain.WALL) {
        n++;
      }
      if (map[i - 1] == Terrain.WALL) {
        n++;
      }
      if (map[i + WIDTH] == Terrain.WALL) {
        n++;
      }
      if (map[i - WIDTH] == Terrain.WALL) {
        n++;
      }
      if (Random.Int(6) <= n) {
        map[i]=Terrain.EMPTY_DECO;
      }
    }
  }
  for (int i=0; i < LENGTH; i++) {
    if (map[i] == Terrain.WALL && Random.Int(12) == 0) {
      map[i]=Terrain.WALL_DECO;
    }
  }
  while (true) {
    int pos=roomEntrance.random();
    if (pos != entrance) {
      map[pos]=Terrain.SIGN;
      break;
    }
  }
  if (Dungeon.bossLevel(Dungeon.depth + 1)) {
    return;
  }
  for (  Room r : rooms) {
    if (r.type == Type.STANDARD) {
      for (      Room n : r.neigbours) {
        if (n.type == Type.STANDARD && !r.connected.containsKey(n)) {
          Rect w=r.intersect(n);
          if (w.left == w.right && w.bottom - w.top >= 5) {
            w.top+=2;
            w.bottom-=1;
            w.right++;
            Painter.fill(this,w.left,w.top,1,w.height(),Terrain.CHASM);
          }
 else           if (w.top == w.bottom && w.right - w.left >= 5) {
            w.left+=2;
            w.right-=1;
            w.bottom++;
            Painter.fill(this,w.left,w.top,w.width(),1,Terrain.CHASM);
          }
        }
      }
    }
  }
}

Fixed version (ground truth):
@Override protected void decorate(){
  for (  Room room : rooms) {
    if (room.type != Room.Type.STANDARD) {
      continue;
    }
    if (room.width() <= 3 || room.height() <= 3) {
      continue;
    }
    int s=room.square();
    if (Random.Int(s) > 8) {
      int corner=(room.left + 1) + (room.top + 1) * WIDTH;
      if (map[corner - 1] == Terrain.WALL && map[corner - WIDTH] == Terrain.WALL) {
        map[corner]=Terrain.WALL;
      }
    }
    if (Random.Int(s) > 8) {
      int corner=(room.right - 1) + (room.top + 1) * WIDTH;
      if (map[corner + 1] == Terrain.WALL && map[corner - WIDTH] == Terrain.WALL) {
        map[corner]=Terrain.WALL;
      }
    }
    if (Random.Int(s) > 8) {
      int corner=(room.left + 1) + (room.bottom - 1) * WIDTH;
      if (map[corner - 1] == Terrain.WALL && map[corner + WIDTH] == Terrain.WALL) {
        map[corner]=Terrain.WALL;
      }
    }
    if (Random.Int(s) > 8) {
      int corner=(room.right - 1) + (room.bottom - 1) * WIDTH;
      if (map[corner + 1] == Terrain.WALL && map[corner + WIDTH] == Terrain.WALL) {
        map[corner]=Terrain.WALL;
      }
    }
    for (    Room n : room.connected.keySet()) {
      if ((n.type == Room.Type.STANDARD || n.type == Room.Type.TUNNEL) && Random.Int(3) == 0) {
        Painter.set(this,room.connected.get(n),Terrain.EMPTY_DECO);
      }
    }
  }
  for (int i=WIDTH + 1; i < LENGTH - WIDTH; i++) {
    if (map[i] == Terrain.EMPTY) {
      int n=0;
      if (map[i + 1] == Terrain.WALL) {
        n++;
      }
      if (map[i - 1] == Terrain.WALL) {
        n++;
      }
      if (map[i + WIDTH] == Terrain.WALL) {
        n++;
      }
      if (map[i - WIDTH] == Terrain.WALL) {
        n++;
      }
      if (Random.Int(6) <= n) {
        map[i]=Terrain.EMPTY_DECO;
      }
    }
  }
  for (int i=0; i < LENGTH; i++) {
    if (map[i] == Terrain.WALL && Random.Int(12) == 0) {
      map[i]=Terrain.WALL_DECO;
    }
  }
  placeSign();
  if (Dungeon.bossLevel(Dungeon.depth + 1)) {
    return;
  }
  for (  Room r : rooms) {
    if (r.type == Type.STANDARD) {
      for (      Room n : r.neigbours) {
        if (n.type == Type.STANDARD && !r.connected.containsKey(n)) {
          Rect w=r.intersect(n);
          if (w.left == w.right && w.bottom - w.top >= 5) {
            w.top+=2;
            w.bottom-=1;
            w.right++;
            Painter.fill(this,w.left,w.top,1,w.height(),Terrain.CHASM);
          }
 else           if (w.top == w.bottom && w.right - w.left >= 5) {
            w.left+=2;
            w.right-=1;
            w.bottom++;
            Painter.fill(this,w.left,w.top,w.width(),1,Terrain.CHASM);
          }
        }
      }
    }
  }
}