error[E0038]: the trait `Trait` is not dyn compatible --> $DIR/E0038.rs:5:20 | LL | fn call_foo(x: Box) { | ^^^^^^^^^ `Trait` is not dyn compatible | note: for a trait to be dyn compatible it needs to allow building a vtable for more information, visit --> $DIR/E0038.rs:2:22 | LL | trait Trait { | ----- this trait is not dyn compatible... LL | fn foo(&self) -> Self; | ^^^^ ...because method `foo` references the `Self` type in its return type = help: consider moving `foo` to another trait error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0038`.