Chapter 9.1: Using a panic! Backtrace. Code in listing 9-1 is wrong/outdated.

[ExpressGradient]

There's this code snippet in this section which is an attempt to access an element of a vector using an invalid index.

fn main() {
    let v = vec![1, 2, 3];
    
    v[99];
}

The explanation says, "This error points at a file we didn't write, libcore/slice/mod.rs. That's the implementation of slice in the Rust source code."

But when I run the listing in the browser and also on my local machine, the error points directly at the line where v[99]; is there, thread 'main' panicked at 'index out of bounds: the len is 3 but the index is 99', src/main.rs:4:5, to be precise.

According to the community discord server, the reason for this behavior was, slice was not included in the scope in prelude at the time of writing that part in the book.

[shepmaster]

I don't believe the previous rationale is correct; my guess is that this is due to rust-lang/rust#47809

[ExpressGradient]

ahh makes sense.
But anyhow, the panic message should be updated accordingly then.

[carols10cents]

Thanks, fixed!