error[E0277]: `Dummy` doesn't implement `Debug`
   --> $DIR/issue-107649.rs:105:5
    |
105 |     dbg!(lib::Dummy);
    |     ^^^^^^^^^^^^^^^^ `Dummy` cannot be formatted using `{:?}`
    |
    = help: the trait `Debug` is not implemented for `Dummy`
    = note: add `#[derive(Debug)]` to `Dummy` or manually `impl Debug for Dummy`
    = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider annotating `Dummy` with `#[derive(Debug)]`
   --> $DIR/auxiliary/dummy_lib.rs:2:1
    |
2   + #[derive(Debug)]
3   | pub struct Dummy;
    |

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.