New internal lint: unusual_names

[samueltardieu]

This lint aims at detecting unusual names used in Clippy source code, such as appl or application for a rustc_errors::Applicability variable, instead of app and applicability which are commonly used throughout Clippy.

This helps maintaining the consistency of the Clippy source code.

It is currently implemented for:

• Applicability: app or applicability
• EarlyContext/LateContext: cx
• TyCtxt: tcx

changelog: none

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[Jarcho]

Seems reasonable. Will wait a bit if anyone on the team has anything to add.

cc @rust-lang/clippy

[Alexendoo]

Sounds fine to me, feels like something we could make into a disallowed- style lint

[allowed-names]
"rustc_errors::Applicability" = ["app", "applicability"]
"rustc_middle::ty::TyCtxt" = "tcx"
# etc

[samueltardieu]

I thought about this and as long as it is an internal lint only we can edit the source as easily as we would edit the configuration file. But if we make it a general lint, it would be a good idea to make it configurable of course.

[rustbot]

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[samueltardieu]

Are there any blockers to merge this new internal lint?

[Jarcho]

I don't think anything actually blocks this. A more general lint can be added later and replace this if it's useful. We already have internal only symbols being added and I have a solution to separate them.

[blyxyas]

The concern I raised is now resolved, if you're looking for it. I'll do an experiment soon and if there isn't anything relevant, just ignore it and let it be.