'required by this formatting parameter' not shown after running examples from ch05-02

[ardrabczyk]

• I have searched open and closed issues and pull requests for duplicates, using these search terms:
  • rect1
• I have checked the latest main branch to see if this has already been fixed, in this file:
  • 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#adding-functionality-with-derived-traits

Description of the problem:

The text says that required by this formatting parameter errors will be shown:

If we continue reading the errors, we’ll find this helpful note:

| |Rectangle cannot be formatted with the default formatter
| required by this formatting parameter

and:

But again, the compiler gives us a helpful note:

| required by this formatting parameter
|

But required by this formatting parameter part is not shown:

root@8b6978f444ca:/workspace# cargo --version
cargo 1.96.0 (30a34c682 2026-05-25)
root@8b6978f444ca:/workspace# cargo run
   Compiling rectangle-print v0.1.0 (/workspace)
error[E0277]: `Rectangle` doesn't implement `std::fmt::Display`
  --> src/main.rs:12:24
   |
12 |     println!("rect1 is {rect1}");
   |                        ^^^^^^^ `Rectangle` cannot be formatted with the default formatter
   |
help: the trait `std::fmt::Display` is not implemented for `Rectangle`
  --> src/main.rs:1:1
   |
 1 | struct Rectangle {
   | ^^^^^^^^^^^^^^^^
   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead

For more information about this error, try `rustc --explain E0277`.
error: could not compile `rectangle-print` (bin "rectangle-print") due to 1 previous error

The same applies to println!("rect1 is {rect1:?}").

Suggested fix:

Replace

println!("rect1 is {rect1}");

with

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

Replace

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

with:

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

Build now:

root@d733377f09d4:/workspace# cargo run
   Compiling rectangle-print v0.1.0 (/workspace)
error[E0277]: `Rectangle` doesn't implement `std::fmt::Display`
  --> src/main.rs:12:29
   |
12 |     println!("rect1 is {}", rect1);
   |                        --   ^^^^^ `Rectangle` cannot be formatted with the default formatter
   |                        |
   |                        required by this formatting parameter
   |
help: the trait `std::fmt::Display` is not implemented for `Rectangle`
  --> src/main.rs:1:1
   |
 1 | struct Rectangle {
   | ^^^^^^^^^^^^^^^^
   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead

error[E0277]: `Rectangle` doesn't implement `Debug`
  --> src/main.rs:13:31
   |
13 |     println!("rect1 is {:?}", rect1);
   |                        ----   ^^^^^ `Rectangle` cannot be formatted using `{:?}` because it doesn't implement `Debug`
   |                        |
   |                        required by this formatting parameter
   |
   = help: the trait `Debug` is not implemented for `Rectangle`
   = note: add `#[derive(Debug)]` to `Rectangle` or manually `impl Debug for Rectangle`
help: consider annotating `Rectangle` with `#[derive(Debug)]`
   |
 1 + #[derive(Debug)]
 2 | struct Rectangle {
   |

For more information about this error, try `rustc --explain E0277`.
error: could not compile `rectangle-print` (bin "rectangle-print") due to 2 previous errors