Lifetime in struct

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2

Let's assign some numbers to those elided and anonymous lifetimes (not real Rust syntax):

impl HighScores<'1> {
    //          ^^
    pub fn new(scores: &'2 [u32]) -> Self { ... }
    //                  ^^
}

Self is HighScores<'1>, so what this says is that new can take a slice of any lifetime '2 and return a HighScores of any lifetime '1. What you want to say is that you can take a slice of some lifetime and return a HighScores of the same lifetime:

impl<'a> HighScores<'a> {
    pub fn new(scores: &'a [u32]) -> Self { ... }
}

Since new returns Self, its argument has to be a reference of the same lifetime as Self. To do that we have to declare a named lifetime parameter and use it both in the impl and in the signature of new.

Lifetime elision doesn't mean lifetime inference: the compiler isn't looking at how you're using the lifetimes and filling them in with what makes sense. It's a pretty simple set of rules that only takes into account the current signature. An elided lifetime ('2) never unifies with a lifetime parameter from an outer scope ('1).

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