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add array::from_ref #77074

Merged
merged 3 commits into from
Sep 25, 2020
Merged

add array::from_ref #77074

merged 3 commits into from
Sep 25, 2020

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lcnr
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@lcnr lcnr commented Sep 22, 2020 •
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mirrors the methods in std::slice with the same name.

I guess this method previously didn't exist as there was close to no reason to create an array of size 1.
This will change due to const generics in the near future.

@rust-highfive
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r? @cramertj

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@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 22, 2020
@lcnr lcnr changed the title add array from_ref add array::from_ref Sep 22, 2020
@tspiteri tspiteri mentioned this pull request Sep 23, 2020
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@lcnr lcnr mentioned this pull request Sep 23, 2020
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@SimonSapin
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This is new unstable safe API that would be very easy to re-implement, but require unsafe. It is rather niche, but follows the precedent of similar functions in std::slice. At least one person asked about exactly this: https://www.reddit.com/r/rust/comments/ixqzkf/are_there_any_gotchas_to_converting_t_into_t_1/

@rust-lang/libs Does anyone feel this should not be merged and eventually stabilized?

@sfackler
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I'm not really opposed, but why will const generics change the usefulness of this method?

@lcnr
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lcnr commented Sep 23, 2020 •
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const generics makes working with arrays easier, which will result in more methods to both create and use arrays.

@emilazy
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emilazy commented Sep 23, 2020

Just wanted to point out that slice::from_{ref,mut} can both be reimplemented more simply in terms of array::from_{ref,mut} due to &[T; 1] automatically decaying to &[T], so this API can be added with no net increase of unsafe usage and arguably decreases the subtlety of the safety justifications.

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Good point @emilazy.

@lcnr, could you make the change in this PR? r=me with that.

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lcnr commented Sep 23, 2020

@bors r=SimonSapin rollup

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bors commented Sep 23, 2020

📌 Commit 5b30161 has been approved by SimonSapin

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 23, 2020
@jonas-schievink jonas-schievink mentioned this pull request Sep 25, 2020
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bors added a commit to rust-lang-ci/rust that referenced this pull request Sep 25, 2020
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Auto merge of rust-lang#77172 - jonas-schievink:rollup-a041rou, r=jon…
5bfeee5 
…as-schievink

Rollup of 15 pull requests

Successful merges:

 - rust-lang#75438 (Use adaptive SVG favicon for rustdoc like other rust sites)
 - rust-lang#76304 (Make delegation methods of `std::net::IpAddr` unstably const)
 - rust-lang#76724 (Allow a unique name to be assigned to dataflow graphviz output)
 - rust-lang#76978 (Documented From impls in std/sync/mpsc/mod.rs)
 - rust-lang#77044 (Liballoc bench vec use mem take not replace)
 - rust-lang#77050 (Typo fix: "satsify" -> "satisfy")
 - rust-lang#77074 (add array::from_ref)
 - rust-lang#77078 (Don't use an if guard to check equality with a constant)
 - rust-lang#77079 (Use `Self` in docs when possible)
 - rust-lang#77081 (Merge two almost identical match arms)
 - rust-lang#77121 (Updated html_root_url for compiler crates)
 - rust-lang#77136 (Suggest `const_mut_refs`, not `const_fn` for mutable references in `const fn`)
 - rust-lang#77160 (Suggest `const_fn_transmute`, not `const_fn`)
 - rust-lang#77164 (Remove workaround for deref issue that no longer exists.)
 - rust-lang#77165 (Followup to rust-lang#76673)

Failed merges:

r? `@ghost`
@bors bors merged commit 09b0bd6 into rust-lang:master Sep 25, 2020
@rustbot rustbot added this to the 1.48.0 milestone Sep 25, 2020
@lcnr lcnr deleted the array-from-ref branch September 25, 2020 06:27
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