[tuple_array_conversions]: move from complexity to nursery

[MingweiSamuel]

The lint suggestion is arguably often less readable and more complex than the original code.

For example, which of the following is the most readable:

let _vertices = edges.flat_map(|(src, dst)| [src, dst]);
let _vertices = edges.flat_map(<_ as Into<[i32; 2]>>::into);
let _vertices = edges.flat_map(<[i32; 2]>::from);

The lint can be useful, but really only applies if the tuple is either long enough that naming the fields is silly (maybe at least 4 entries long), or if the author intends the fields to be homogenous, which is author intent and can't be determined by the lint. Therefore I think the lint should be marked as pedantic.

Currently, there are also a lot of false positives with the lint:

• tuple_array_conversions lint makes code less readable when slice is involved #11082
• tuple_array_conversions suggested code erases binding names and hides asymmetry #11085
• tuple_array_conversions misses implicit &mut -> & conversion subtelty #11100 ([tuple_array_conversions]: Check if all types are same #11105)
• tuple_array_conversions triggers even when binding is used for more than tuple-array conversion #11124
• tuple_array_conversion false positive on destructured tuple values #11144

Should fix those issues before enabling it for everyone.

---

changelog: Move [tuple_array_conversions] to nursery (Now allow-by-default)

#11146

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @dswij (or someone else) soon.

Please see the contribution instructions for more information. Namely, in order to ensure the minimum review times lag, PR authors and assigned reviewers should ensure that the review label (S-waiting-on-review and S-waiting-on-author) stays updated, invoking these commands when appropriate:

• @rustbot author: the review is finished, PR author should check the comments and take action accordingly
• @rustbot review: the author is ready for a review, this PR will be queued again in the reviewer's queue

[Centri3]

This should be nursery instead.

I'll try to fix most of these issues before the next sync (in 2 weeks).

[MingweiSamuel]

Ok, that makes sense too!

[Centri3]

Bit sad about this but it makes sense. Once it's been rewritten hopefully we can bump it up to pedantic, likely not complexity as the lost asymmetry is a big issue. Which is unfortunate since this lint was kinda meant as a learning tool.

[Centri3]

For example, which of the following is the most readable:

Will say though that IMO it's the third, it conveys the intent best (if it's not asymmetric) and even avoids an unnecessary closure which is pretty nice

[xFrednet]

LGTM, thank you for the PR 👍 I believe this move makes sense for the time being.

The version says 1.72.0, we should be able to back port this move to beta.

r? @xFrednet

@bors r=Centri3,xFrednet

[bors]

📌 Commit 4102a30 has been approved by Centri3,xFrednet

It is now in the queue for this repository.

[bors]

⌛ Testing commit 4102a30 with merge 631faa1...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: Centri3,xFrednet
Pushing 631faa1 to master...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: Centri3,xFrednet
Pushing 631faa1 to master...