error[E0107]: this enum takes 2 generic arguments but 1 generic argument was supplied
  --> $DIR/issue-65159.rs:5:20
   |
LL | async fn copy() -> Result<()>
   |                    ^^^^^^ -- supplied 1 generic argument
   |                    |
   |                    expected 2 generic arguments
   |
note: enum defined here, with 2 generic parameters: `T`, `E`
  --> $SRC_DIR/core/src/result.rs:LL:COL
   |
LL | pub enum Result<T, E> {
   |          ^^^^^^ -  -
help: add missing generic argument
   |
LL | async fn copy() -> Result<(), E>
   |                             +++

error: aborting due to previous error

For more information about this error, try `rustc --explain E0107`.