error[E0277]: `main` has invalid return type `ReturnType` --> $DIR/termination-trait-not-satisfied.rs:3:14 | LL | fn main() -> ReturnType { | ^^^^^^^^^^ `main` can only return types that implement `Termination` | = help: consider using `()`, or a `Result` error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0277`.