rust_ex7.cpp

struct A {
    int x;
};

struct B: A {
    int y;
};

struct C: B {
    int z;
};

B func(B arg)
{
    return arg;
}

int main() {
    A a;
    B b;
    /* this works fine:
     * a B value is a valid A value
     * to put it another way, you can use a B value
     * whenever an A value is expected
     */
    a = b;
    /* on the other hand,
     * this would be an error:
     */

    // b = a;

    // this works just fine
    C arg;
    A res = func(arg);
    return 0;
}