C++ 无效使用未定义类型'structsquare'

我正在制作一个解决一个数独游戏的程序，但我收到了一个错误，从我的编译器.

error: invalid use of undefined type ‘struct Square’
   30 |         if(box->squares[x]->possible[number-1] == 0){
                                  ^~

功能是:

int updateBoxes(Square *** sudoku, int row, int column){
    int x;
    int number = sudoku[row][column]->number;
    Box * box;
    box = sudoku[row][column]->box;

    for(x = 0; x < SIZE_ROWS; x++){
        if(box->squares[x]->possible[number-1] == 0){
            box->squares[x]->solvable--;
            box->squares[x]->possible[number-1] = 1;
        }
    }
    return 1;
}

错误也出现在后面两行.

Square和Box的定义是:

typedef struct box
{
    struct Square ** squares;  /* array of Squares */
    int numbers;
    int possible[9];
    int solvable;
    struct Box * next;
} Box;

/* square is a single number in the board */
typedef struct square
{
    int number;     
    int possible[9];
    /*
       the array is only made of 0 and 1
       each index corresponds to a number: ex: index 4 == number 5 ...
       1 tells me that 5 cannot go into this scare
       0 tells me that 5 can go into this scare
    */
    int solvable;   /* will be subtracted 1 each time and when it is 1 it's because is solvable */
    Box * box;      /* tells me the corresponding box */
    int row;
    int column;
} Square;

我在YouTube上遵循一个教程，这个家伙没有得到我得到的错误，YouTube视频是: https://www.youtube.com/watch?v=CnzrCBLCDhc&t=1326s