error[E0277]: `NotDebug` doesn't implement `Debug`
  --> $DIR/dbg-macro-requires-debug.rs:6:23
   |
LL |     let _: NotDebug = dbg!(NotDebug);
   |                       ^^^^^^^^^^^^^^ `NotDebug` cannot be formatted using `{:?}`
   |
   = help: the trait `Debug` is not implemented for `NotDebug`, which is required by `&NotDebug: Debug`
   = note: add `#[derive(Debug)]` to `NotDebug` or manually `impl Debug for NotDebug`
   = note: this error originates in the macro `$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 `NotDebug` with `#[derive(Debug)]`
   |
LL + #[derive(Debug)]
LL | struct NotDebug;
   |

error: aborting due to 1 previous error

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