//error: struct `X' is only partially defined
//error: union `Y' is only partially defined
//error: struct `Z' is only partially defined

struct X {
    int i;
    Y[] y;
};

union Y {
    X;
    Z;
};

struct Z {
    double d;
    X x;
};

protocol mutualRecStructUnion {
child:
    async Test(X x, Y y, Z z);
    async __delete__();
};