error[E0277]: `Error` doesn't implement `Debug`
  --> $DIR/derives-span-Debug-struct.rs:8:5
   |
LL | #[derive(Debug)]
   |          ----- in this derive macro expansion
LL | struct Struct {
LL |     x: Error
   |     ^^^^^^^^ the trait `Debug` is not implemented for `Error`
   |
   = note: add `#[derive(Debug)]` to `Error` or manually `impl Debug for Error`
help: consider annotating `Error` with `#[derive(Debug)]`
   |
LL + #[derive(Debug)]
LL | struct Error;
   |

error: aborting due to 1 previous error

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