`clippy::borrowed_box` is denied by the workspace lint set, and the closure
added with the optics exclusion took `&Box<dyn Operation>` — a borrow of the
box rather than of the thing in it, which says nothing the plain trait object
does not.
Caught by `cargo clippy --workspace --all-targets -- -D warnings`, which is
what CI runs and what the workspace tests do not: a lint on test code only
appears when the tests are compiled as a clippy target.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>