Dereferencing seems to be used in the book before it's explained

[estebank]

From rust-lang/rust#55969

The Rust book (2018 edition) uses the following example in chapter 10 (comments added by me)

fn largest(list: &[i32]) -> i32 {
    let mut largest = list[0];  // i32

    for &item in list.iter() {  // item is &i32
        if item > largest {
            largest = item;
        }
    }

    largest
}

This was and still is puzzling to me for several reasons:

1. list is &[i32], so I'd expect list[0] to be &i32. Instead, list[0] is i32...
2. which is extra weird because list.iter() seems to yield &i32's.
3. Finally, what the heck is &item? I thought & made references, but here it seems to do the opposite.

I gather that there's some kind of implicit dereferencing going on when we do list[0], and I guess &item is also a dereference. It would be nice if this were explained in the book before it shows up in the example.

[carols10cents]

Yes, we could add a note here that the usage of the iterator will be explained in chapter 13... that part of the code isn't what we're trying to showcase in this example, so we are deliberately glossing over it but we could be explicitly glossing over it :)