error: #[derive(Metrics)] can only be placed on structs
 --> tests/ui/metrics/unsupported_item.rs:4:1
  |
4 | enum Unsupported {}
  | ^^^^^^^^^^^^^^^^^^^

error: Only named fields are supported
 --> tests/ui/metrics/unsupported_item.rs:7:23
  |
7 | struct UnsupportedToo(u8);
  |                       ^^