error[E0277]: the trait bound `Self: std::cmp::Eq` is not satisfied
  --> $DIR/wf-trait-default-fn-ret.rs:11:5
   |
LL |   struct Bar<T:Eq+?Sized> { value: Box<T> }
   |   ----------------------- required by `Bar`
...
LL | /     fn bar(&self) -> Bar<Self> {
LL | |
LL | |         //
LL | |         // Here, Eq ought to be implemented.
LL | |         loop { }
LL | |     }
   | |_____^ the trait `std::cmp::Eq` is not implemented for `Self`
   |
   = help: consider adding a `where Self: std::cmp::Eq` bound

error: aborting due to previous error

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