What mistake I am doing here in C code

typedef union
{
    struct
    {
        int8_t   a;
        int16_t  b;
        uint32_t c;
    };

    int8_t my_arr[7];
}x;

uint8_t arr[7];

int main( void )
{
    uint32_t i;
    x *y;

    for( i = 0 ; i < 7 ; i++ )
    {
        arr[i] = i + 2 * 5;
    }

    y = ( x* )arr;

    i = y->a;
    i = y->b;
    i = y->c;
}