How to access different struct type member in MACRO?

#include 
struct s1 { int x; };
struct s2 { int y; };
#define MYMACRO(val) Generic((val),   \
    struct s1: handles1,               \
    struct s2: handles2                \
)(&(val))
void handles1(struct s1 *s) { s->x = 10; }
void handles2(struct s2 *s) { s->y = 20; }
int main() {
    struct s1 a;
    struct s2 b;
    MYMACRO(a);
    MYMACRO(b);
    printf("a.x = %d, b.y = %d\n", a.x, b.y);
}

_Generic does compile-time type dispatch — each branch is only compiled for the matching type, so no "missing member" errors.