error: expected `struct`

         = help: Use `#[quantity]
       ...
       struct <ident> {}`.

  --> tests/ui/item_not_struct.rs:12:1
   |
12 | / /// Foo, a completely useless quantity
13 | | #[quantity]
14 | | #[ref_unit(A, "a", MEGA)]
15 | | #[unit(B, "b", 0.4)]
...  |
18 | |     baz,
19 | | }
   | |_^