1error[E0277]: `MyError` doesn't implement `std::fmt::Display` 2 --> tests/ui/missing-display.rs:4:10 3 | 43 | #[derive(Error, Debug)] 5 | ----- in this derive macro expansion 64 | pub enum MyError { 7 | ^^^^^^^ `MyError` cannot be formatted with the default formatter 8 | 9 = help: the trait `std::fmt::Display` is not implemented for `MyError` 10 = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead 11note: required by a bound in `std::error::Error` 12 --> $RUST/core/src/error.rs 13 | 14 | pub trait Error: Debug + Display { 15 | ^^^^^^^ required by this bound in `Error` 16 = note: this error originates in the derive macro `Error` (in Nightly builds, run with -Z macro-backtrace for more info) 17