Rollup merge of #30115 - nilcons-contrib:fix-book-stack, r=steveklabnik

The `f` argument will reference the actual value in the `d` box, not the box in the `bar`'s stack frame.

I am just learning Rust, so I don't know how to explain this well, but just from `f`'s type it is clear that it will be a pointer to an `i32`, not a pointer to a pointer. Some `println!("{:p}", ...)`'s can easily confirm this.

I would actually suggest to remove/simplify this part of the example. This is a subtle issue that can easily confuse people at the early stages of familiarizing with the language. (As I got confused by it. :))

Author: steveklabnik

src/doc/book/the-stack-and-the-heap.md

@@ -464,7 +464,7 @@ At the end of `bar()`, it calls `baz()`:
 | (2<sup>30</sup>) - 2 |      | 5                      |
 | ...                  | ...  | ...                    |
 | 12                   | g    | 100                    |
-| 11                   | f    | → 9                    |
+| 11                   | f    | → (2<sup>30</sup>) - 2 |
 | 10                   | e    | → 9                    |
 | 9                    | d    | → (2<sup>30</sup>) - 2 |
 | 8                    | c    | 5                      |