Should freeze the property passed to component

[Javey]

When we pass a Object to child component, the child component may change the property of that Object. But the $change event can not to be triggered.

class A extends Intact {
     defauts() {
        return {data: {}};
    },
    change() {
        // this set will trigger '$change:data.a' and '$change:data' events
        this.set('data.a', 1);
   }
}

// when the users has changed by `change` method of A component
// we can not get the `$change:user.a` and `$change:user` events
<A data={self.get('user')} />

So we should freeze the property which passed to child component.