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

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

struct Y {
    X x;
    Z z;
};

struct Z {
    double d;
    X x;
};

[ChildProc=any]
protocol mutualRecStruct {
child:
    async Test(X x, Y y, Z z);
    async __delete__();
};