我认为您是对的，没有不安全的代码就不可能做到这一点.我会考虑以下两个选项:

I think you're right in that it's not possible to do this without unsafe code. I would consider the following two options:

1. 将 Bar 中的引用更改为索引.框内的内容不受借用保护，因此如果您不小心，索引可能会失效.但是，索引可能会以更清晰的方式传达引用的含义.

1. Change the reference in Bar to an index. The contents of the box won't be protected by a borrow, so the index might become invalid if you're not careful. However, an index might convey the meaning of the reference in a clearer way.

将Box移动到Bar中，并添加一个函数buf() ->&[u8] 到 Bar 的实现；而不是引用，将索引存储在 Bar 中.现在 Bar 是缓冲区的所有者，因此它可以控制其修改并保持索引有效(从而避免选项 #1 的问题).

Move Box<[u8]> into Bar, and add a function buf() -> &[u8] to the implementation of Bar; instead of references, store indices in Bar. Now Bar is the owner of the buffer, so it can control its modification and keep the indices valid (thereby avoiding the problem of option #1).

根据下面 DK 的建议，将索引存储在 BarWithBuf(或辅助结构 BarInternal)中并添加函数 fn bar(&自我)->Bar 到 BarWithBuf 的实现，它会即时构造一个 Bar.

As per DK's suggestion below, store indices in BarWithBuf (or in a helper struct BarInternal) and add a function fn bar(&self) -> Bar to the implementation of BarWithBuf, which constructs a Bar on-the-fly.

这些选项中哪一个最合适取决于实际的问题上下文.我同意某种形式的逐个成员构造"结构在 Rust 中会非常有帮助.

Which of these options is the most appropriate one depends on the actual problem context. I agree that some form of "member-by-member construction" of structs would be immensely helpful in Rust.