1 error[E0107]: this enum takes 2 generic arguments but 1 generic argument was supplied
2 --> $DIR/issue-65159.rs:5:20
4 LL | async fn copy() -> Result<()>
5 | ^^^^^^ -- supplied 1 generic argument
7 | expected 2 generic arguments
9 help: add missing generic argument
11 LL | async fn copy() -> Result<(), E>
14 error: aborting due to previous error
16 For more information about this error, try `rustc --explain E0107`.