Bump to Rust 1.84

[coolreader18]

Description of Changes

This was discussed as something we wanted to do before the 1.0 release.

Expected complexity level and risk

1

cc @clockworklabs/devops

[gefjon]

Please don't include unrelated changes in PRs like this. As a reviewer, I don't want to sort through what changed as a result of bumping to the new Rust version versus what drive-by fixes you made. If you feel that the unrelated changes are worthwhile (all of them look good to me), please open a separate PR. I would approve "reformat doc comments to correctly indent multi-line list items" in a heartbeat, for example.

[coolreader18]

All the changes are fixing warnings that were added sometime in the past 4 versions. That's one of the benefits of keeping up to date with stable rust; less churn in updating wrt rustc/clippy warnings (perhaps we could run CI clippy on latest stable?). The doc-comment formatting changes are all related to a new lint complaining about lists not being indented correctly, and all the cfg-related changes are related to the new check-cfgs lint, that makes sure you don't accidentally typo to e.g. a feature that doesn't exist (as in a couple cases here). And yes, rustc's unused-detection was improved, I think to check for when something declared pub isn't actually publically exposed or used anywhere in the crate. The mem::transmute thing is from a new clippy lint requiring that you specify the T, U type parameters, which I'd agree is definitely best practice - makes it easy to see at a glance what the conversion actually is, instead of having to trace the type inference yourself (or to be using an IDE).

[gefjon]

That's one of the benefits of keeping up to date with stable rust; less churn in updating wrt rustc/clippy warnings (perhaps we could run CI clippy on latest stable?).

Running Clippy on latest stable seems eminently reasonable. Updating our MSRV every month does not. It is very much the point of a Minimum Supported Rust Version that it should be the lowest possible version.

The doc-comment formatting changes are all related to a new lint complaining about lists not being indented correctly, and all the cfg-related changes are related to the new check-cfgs lint, that makes sure you don't accidentally typo to e.g. a feature that doesn't exist (as in a couple cases here). And yes, rustc's unused-detection was improved, I think to check for when something declared pub isn't actually publically exposed or used anywhere in the crate. The mem::transmute thing is from a new clippy lint requiring that you specify the T, U type parameters, which I'd agree is definitely best practice - makes it easy to see at a glance what the conversion actually is, instead of having to trace the type inference yourself (or to be using an IDE).

In the future, please add this level of commentary to the PR description before requesting review.

[coolreader18]

Fair enough; I think I figured it was self-explanatory but obviously it wasn't.

[bfops]

Approving the changes in my code-owned files (crates/cli/src/config.rs and crates/cli/src/errors.rs)

[cloutiertyler]

I am approving the changes to the files I am an owner of. I echo Phoebe's suggestion about adding commentary in the PR description in the future.