error[E0277]: the trait bound `[async block@$DIR/issue-55872-3.rs:16:9: 16:17]: Copy` is not satisfied --> $DIR/issue-55872-3.rs:14:20 | LL | fn foo() -> Self::E { | ^^^^^^^ the trait `Copy` is not implemented for `[async block@$DIR/issue-55872-3.rs:16:9: 16:17]` error: aborting due to previous error For more information about this error, try `rustc --explain E0277`.