Documentation on returning closures is confusing

[Tonkpils]

Going through the Rust book on the Returning Closures section, I found the code suddenly switches the factory function from using Vec<i32> to i32 and without explanation

fn factory() -> (Fn(i32) -> Vec<i32>) {
    let vec = vec![1, 2, 3];

    |n| vec.push(n)
}

...

fn factory() -> &(Fn(i32) -> Vec<i32>) {
    let vec = vec![1, 2, 3];

    |n| vec.push(n)
}

let f = factory();

let answer = f(4);
assert_eq!(vec![1, 2, 3, 4], answer);
But we get another error:

error: missing lifetime specifier [E0106]
fn factory() -> &(Fn(i32) -> i32) {
                ^~~~~~~~~~~~~~~~~
Right. Because we have a reference, we need to give it a lifetime. But our factory() function takes no arguments, so elision doesn’t kick in here. What lifetime can we choose? 'static:

fn factory() -> &'static (Fn(i32) -> i32) {
    let num = 5;

    |x| x + num
}

let f = factory();

let answer = f(1);
assert_eq!(6, answer);

This caused a bit of confusion, specially when trying to use the given solution to returning closures with Vec<i32> since using the solution throws an error with that type:

fn factory() -> Box<Fn(i32) -> Vec<i32>> {
    let vec = vec![1, 2, 3];

    Box::new(move |n| vec.push(n))
}

src/main.rs:44:23: 44:34 error: mismatched types:
 expected `collections::vec::Vec<i32>`,
    found `()`
(expected struct `collections::vec::Vec`,
    found ()) [E0308]
src/main.rs:44     Box::new(move |n| vec.push(n))
                                     ^~~~~~~~~~~
error: aborting due to previous error
Could not compile `learning_rust`.

To learn more, run the command again with --verbose.

Am I missing something here or should the documentation use i32 from the beginning of the section? If there's anything I can do to help with this I'd be glad to make a PR.

[steveklabnik]

I think @jimblandy may have fixed this with a recent patch. Jim?

[Tonkpils]

Yeah, it looks like it's been fixed #26191