error: `#[derive(Subcommand)]` only supports enums
 --> $DIR/subcommand_on_struct.rs:3:10
  |
3 | #[derive(Subcommand, Debug)]
  |          ^^^^^^^^^^
  |
  = note: this error originates in the derive macro `Subcommand` (in Nightly builds, run with -Z macro-backtrace for more info)