error: `darth` already exists, having another argument having almost the same name makes code comprehension and documentation more difficult
  --> $DIR/duplicate_underscore_argument.rs:4:23
   |
LL | fn join_the_dark_side(darth: i32, _darth: i32) {}
   |                       ^^^^^
   |
   = note: `-D clippy::duplicate-underscore-argument` implied by `-D warnings`

error: aborting due to previous error