typedef U = union (int i, bool b);

() test() {
    var U a;
    var union (int i, bool b) b;
    var union (int i, bool b) c;
    var union (int, bool) d;
    
    a = b;
    a = c;
    a = d;
    
    b = a;
    b = c;
    b = d;
    
    c = a;
    c = b;
    c = d;
    
    d = a;
    d = b;
    d = c;
}