[.rs] Suboptimal diff when replacing macro with negated if statement

[merrybot]

Thanks for reporting a bug! Please include all of the following:

(1) A description of the issue. A screenshot is often helpful too.

Output of git diff using difft:

VSCode's diff puts 139 at the end:

Github's:

(2) A copy of what you're diffing. If you're diffing files, include
the before and after files. If you're using difftastic with a VCS
repository (e.g. git), include the URL and commit hash.

lib.rs at berrymot/notoize@13575c2; hash 13575c20e635c703902ecc681ebcfdef954a7527

(3) The version of difftastic you're using (see difft --version) and
your operating system.

0.55.0; Windows 11. Also difft -v fails, as does the suggested difft -- -v: