7.14.5 is

• 预期：string

用于 动态组件，且基于 DOM 内模板的限制 来工作。

• 示例：

<!-- component changes when currentView changes -->
<component v-bind:is="currentView"></component>

<!-- necessary because `<my-row>` would be invalid inside -->
<!-- a `<table>` element and so would be hoisted out      -->
<table>
  <tr is="my-row"></tr>
</table>