error[E0277]: the trait bound `Self: std::cmp::Eq` is not satisfied --> $DIR/wf-trait-default-fn-arg.rs:11:22 | LL | struct Bar { value: Box } | --- -- required by this bound in `Bar` ... LL | fn bar(&self, x: &Bar) { | ^^^^^^^^^^ - help: consider further restricting `Self`: `where Self: std::cmp::Eq` | | | the trait `std::cmp::Eq` is not implemented for `Self` error: aborting due to previous error For more information about this error, try `rustc --explain E0277`.