error[E0277]: `MyError` doesn't implement `std::fmt::Display` --> $DIR/issue-71363.rs:4:28 | 4 | impl std::error::Error for MyError {} | ^^^^^^^ `MyError` cannot be formatted with the default formatter | = help: the trait `std::fmt::Display` is not implemented for `MyError` = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead note: required by a bound in `std::error::Error` --> $SRC_DIR/core/src/error.rs:LL:COL error[E0277]: `MyError` doesn't implement `Debug` --> $DIR/issue-71363.rs:4:28 | 4 | impl std::error::Error for MyError {} | ^^^^^^^ `MyError` cannot be formatted using `{:?}` | = help: the trait `Debug` is not implemented for `MyError` = note: add `#[derive(Debug)]` to `MyError` or manually `impl Debug for MyError` note: required by a bound in `std::error::Error` --> $SRC_DIR/core/src/error.rs:LL:COL help: consider annotating `MyError` with `#[derive(Debug)]` | 3 | #[derive(Debug)] | error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0277`.