text: #include "smack.h"
  #include <stdio.h>
  #include <stdlib.h>
  
  // @expect verified
  
  typedef struct {
    int x;
  } S1;
  
  typedef struct {
    int a;
    int b;
  } S2;
  
  int main(void) {
    S2 *s2 = (S2 *)malloc(sizeof(S2));
    S1 *s1 = (S1 *)s2;
  
    s2->a = 3;
    s2->b = 5;
    s1->x = 4;
  
    assert(s2->a == 4);
    return 0;
  }
  