Example in documentation about rust SDK to use Cow<'static, str> seems to be misleading.

[CodeServant]

I tried to understand why I should use Cow<'static, str> instead of String as in the example in documentation. I came to the conclusion that the example is misleading besause it says that

// Pro tip: Replace String with Cow<'static, str> to
// avoid unnecessary heap allocations when inserting

#[derive(Serialize, Deserialize)]
struct Name {
    first: Cow<'static, str>,
    last: Cow<'static, str>,
}

So comment says that i should do it to avoid unnecesary allocation while inserting. In some cases serde optimizes with just borrowing the &str. But the problem is that, with the provided example, it only does that for hardcoded string literals. I found explaination here for Cow<'static, str> that it is basically replacement for &str.

This example works because there is hardcoded literal. But to actually be practical should look like this which is impossible with static.
So the example should look like this.

#[derive(Serialize, Deserialize)]
struct Name<'a> {
    first: Cow<'a, str>,
    last: Cow<'a, str>,
}

So here is my question. Is the documentation right? Mayby I am missing something.