Tidy up maybe_uninit_write_slice API

[SUPERCILEX]

• Move methods to extensions

[rustbot]

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

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[rust-highfive]

r? @scottmcm

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[scottmcm]

Thanks for the PR!

While I'm sometimes willing to add new APIs without libs-api assent, I'm much more worried about churning signatures without contacting them to see if they like them, since it would be a shame to find out they didn't and have to revert it and have impacted nightly users unnecessarily.

Could you please file an ACP for this set of changes (I think #103128 #103130 #103131 could probably all be one) to get a "yup, that seems better" from the team?

@rustbot author

[bors]

☔ The latest upstream changes (presumably #108538) made this pull request unmergeable. Please resolve the merge conflicts.

[Dylan-DPC]

@SUPERCILEX any updates on this?

[SUPERCILEX]

I'm not quite sure what the status is: rust-lang/libs-team#122 (comment)

We generally agreed that these slice methods shouldn't exist, but they'll probably be here for a while. I do think that if we end up stabilizing them, it should be like this, not as a static method. The hope would be that they never need to get stabilized though.

[SUPERCILEX]

See rust-lang/libs-team#122 (comment). These are a bit too heavy weight to become inherent methods. I still think they should be renamed, but that can be discussed before stabilization.