$ cargo run
Compiling rectangles v0.1.0 (file:///projects/rectangles)
error[E0277]: `Rectangle` doesn't implement `Debug`
--> src/main.rs:12:31
|
12 | println!("rect1 is {:?}", rect1);
| ^^^^^ `Rectangle` cannot be formatted using `{:?}`
= help: the trait `Debug` is not implemented for `Rectangle`
= note: add `#[derive(Debug)]` to `Rectangle` or manually `impl Debug for Rectangle`
= note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
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 `rectangles` (bin "rectangles") due to 1 previous error
