Can't extend block in component

[Javey]

When pass block to a component, we can't extend it in sub-template.

<Component>
    <b:content>
        <b:body>we can't extend this block(body) in sub-template</b:body>
    </b:content>
</Component>

<b:parent>
     <b:body>the body can't pass to content block of parent's Component</b:body>
</b:parent>

But we can do this by defining parent template like bellow:

const body = <b:body>we can extend this block(body) in sub-template</b:body>

<Component>
    <b:content>{body}</b:content>
</Component>