c/rust · by lysdexic@programming.dev · 3y

Common Rust Lifetime Misconceptions (2020)

https://github.com/pretzelhammer/rust-blog/blob/master/posts/common-rust-lifetime-misconceptions.md

36 points · 5 comments · view on lemmy.world

5 Comments

robinm@programming.dev · 5 pts · 3y (4 replies)

That's a very nicecly written article.

Just a quick question, isn't point 8 outdated (misconctption: “Rust borrow checker does adanced liftime analysis”) due to the introduction NLL (no lexical lifetime) in Rust 2018?

hairyballs@programming.dev · 1 pts · 3y (3 replies)

There are still obvious things the BC cannot get. For example:

struct Foo;

impl Foo {
    fn num(&amp;mut self) -> usize { 0 }
    fn index(&amp;mut self, _i: usize) { }
}

let foo = Foo;
foo.index(foo.num()); //error

sirdorius@programming.dev · 2 pts · 3y

This looks like a pretty easy fix that the compiler could do by extracting the argument to a temp variable to improve the syntax of the language.

KillTheMule@programming.dev · 1 pts · 3y (1 reply)

Note that when you change num to take &self instead, this works out (you also need to mark foo as mutable, of course).

hairyballs@programming.dev · 1 pts · 3y

It's a toy example. In that case, the solution is to assign the expression to a variable to compute its result upfront.