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This post is auto-generated from RSS feed The Rust Programming Language Forum - Latest topics. Source: When and why does this error happen?

Warning: this post contains some bad LLM-code.

Rust beginner here. I read this error which am interested to understand:

An LLM fails to produce an example that fails with the error:

use std::ops::Deref;

fn take_ref(s: &str) {
    println!("{}", s);
}

fn main() {
    let boxed: Box<String> = Box::new("hello".to_string());
    let ref_str: &<Box<String> as Deref>::Target = &*boxed;
    take_ref(ref_str); // ERROR: expected `&str`, found `&String`
}

Besides, I expected ref_str to be &String; the annotation is overwhelming. It seems to mean "The result of deref as implemented for Box<String>".

The LLM-comment is wrong since &String will coerce since a function argument is a type coercion site.
So one expects that to pass, and it does.

I do understand LLMs make mistakes, but since I study their errors and do not paste their output in my codebase, they kind of are for me.
Could you provide help with:

1. A minimal, simple example (or a link to one) to actually reproduce the error at the top
2. Some context / explanation or recommended reading.

I suspect that part of the explanation has to do with the desugaring but can't quite go through it.

Thank you!

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