appearance of dead_code in Debug

[kimpham54]

• I have searched open and closed issues and pull requests for duplicates, using these search terms:
  • field is never read
  • dead_code
• I have checked the latest main branch to see if this has already been fixed, in this file:
  • https://github.com/rust-lang/book/blob/main/src/ch05-02-example-structs.md

URL to the section(s) of the book with this problem:

• https://doc.rust-lang.org/book/ch05-02-example-structs.html
  Description of the problem:
• Not a problem but a nice to have for rust newbies like myself. The appearance of the dead_code warning first appears in this section when running

#[derive(Debug)]
struct Rectangle {
    width: u32,
    height: u32,
}

fn main() {
    let rect1 = Rectangle {
        width: 30,
        height: 50,
    };

    println!("rect1 is {:?}", rect1);
}

Here is my warning message:

warning: fields `width` and `height` are never read
 --> src/main.rs:3:5
  |
2 | struct Rectangle {
  |        --------- fields in this struct
3 |     width: u32,
  |     ^^^^^^^^^^
4 |     height: u32,
  |     ^^^^^^^^^^^
  |
  = note: `#[warn(dead_code)]` on by default
  = note: `Rectangle` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis

Suggested fix:

• it would be nice to explain this for the first time in this chapter that you might see this dead_code message, but it's OK as mentioned in this ticket Chapter 11.1: Getting dead_code warning #2761 which will prevent future bug reports

[chriskrycho]

Thanks, but as with the linked issue, I think this is fine. It's actually important that people learn to read those messages and understand them (and even go look them up!) while reading the book, so having things like this along the way is not a problem but actually useful. And I am glad you learned that it wasn't a problem, so much so that you thought about helping others! Going to close this issue now.