Tooling to find and remove unused derives?

help
1

Do we have any tooling to find and remove unused derived impls?

I've accumulated many unused derived impls in my project and they're causing problems in a few ways:

  • Adding new fields/variants can often cause issues because e.g. the type derives Hash but the new field's type doesn't.

    When this happens the first thing I try is removing the Hash derive. Often I'm able to remove it. It would be great if I could solve this problem automatically.

  • Because there's no direct link from a trait implementation to how use sites, when I look at a type and it derives e.g. Ord I often can't immediately tell why it implements it and whether it needs to implement it.

    If I refactor the code and stop using a derived trait implementation I don't get any warnings so the derive line stays, causing confusion later on.

A tool to remove all unused derives in a package would be really useful. Does something like this already exist?

(My project is not a library, but for libraries maybe it could only do it if it doesn't affect public API.)

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2

I don't know of any tooling that already does this, it'd be helpful to see for types not in the public API.

While this would be different from a semver check, it may be interesting to see if the trustfall framework used for cargo-semver-checks can easily query this kind of thing.