// OK
class P1 extends Payload{
    type = "P1"
}
// OK
class P2 extends Payload {
    type: string;
    constructor() {
        super({ type: "P2" });
    }
}
// OK
class P3 extends Payload{
    constructor() {
        super({ type: "P2" });
    }
}
// OK - It is a bug
class P4 extends Payload{
    // no type
}

// OK
class P1 extends Payload{
    type = "P1"
}
// OK
class P2 extends Payload {
    type: string;
    constructor() {
        super({ type: "P2" });
    }
}
// NG - Need to defined `type: string`
class P3 extends Payload{
    constructor() {
        super({ type: "P2" });
    }
}
// NG: Fix a bug #295 
class P4 extends Payload{
    // no type
}