In what situations can a child element of a VNodeArrayChildren array be another VNodeArrayChildren array?

[kaokei]

We know that a VNode has a property called children, and its type is VNodeNormalizedChildren.
And here are the following type relationships.

type VNodeChildAtom = VNode | string | number | boolean | null | undefined | void;
export type VNodeArrayChildren = Array<VNodeArrayChildren | VNodeChildAtom>;
export type VNodeNormalizedChildren = string | VNodeArrayChildren | RawSlots | null;

The key is why it is export type VNodeArrayChildren = Array<VNodeArrayChildren | VNodeChildAtom>; instead of export type VNodeArrayChildren = Array<VNodeChildAtom>;.

I have made many attempts but haven't found a case where an element of VNodeArrayChildren is itself a VNodeArrayChildren array. It seems that VNodeArrayChildren can only be an array of VNode elements.

Can anyone provide some help?

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什么场景下，VNodeArrayChildren的子元素还是VNodeArrayChildren数组呢？
我尝试了很多场景，也没有复现这个问题。
包括我发现@vue/test-utils这个测试工具库的测试用例中也是没有覆盖这个场景。
如果不存在这个场景，是否应该修改VNodeArrayChildren的类型定义。

[kaokei]

Actually, I discovered this issue while writing test cases for my library and realizing that 100% coverage could not be achieved. Moreover, I found that the test-utils library does not cover this scenario either. You can see that only line 112 is not covered by tests.

@cexbrayat @yyx990803