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Add get_pin_ref and get_pin_mut methods to slice #78370

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Add get_pin_ref and get_pin_mut methods to slice #78370

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taiki-e
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@taiki-e taiki-e commented Oct 25, 2020 •
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This adds methods to return a pinned reference to an element or subslice from a pinned slice.

Motivation: https://users.rust-lang.org/t/working-with-pinned-slices-are-there-any-structurally-pinning-vec-like-collection-types/50634

Suffix (*_pin_{ref, mut}) is based on Option's as_pin_{ref, mut} methods.

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r? @joshtriplett

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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 Oct 25, 2020
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@rustbot rustbot added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Oct 25, 2020
@crlf0710 crlf0710 added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 20, 2020
Aaron1011
Aaron1011 reviewed Nov 20, 2020
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library/core/src/slice/mod.rs
/// ```
#[unstable(feature = "slice_get_pin", issue = "none")]
#[inline]
pub fn get_pin_mut<I>(self: Pin<&mut Self>, index: I) -> Option<Pin<&mut I::Output>>
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The existence of this method means that unsafe code needs to be careful when projecting from a Pin<&mut [T]> to a &mut T (a mutable reference to one of the slice elements). It can still be done soundly, but the &mut T cannot be moved out of if the Pin<&mut [T]> is ever exposed to safe code (which could call get_pin_mut).

I think it would be good to mention this in the docs.

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That is correct. Option::as_pin_mut also has the same issue. We need to add docs to both.

@crlf0710 crlf0710 added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Dec 11, 2020
@JohnCSimon JohnCSimon added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 11, 2021
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taiki-e on Nov 21, 2020
That is correct. Option::as_pin_mut also has the same issue. We need to add docs to both.

assigning back to author - not sure if this is done

@JohnCSimon JohnCSimon added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 1, 2021
@JohnCSimon JohnCSimon added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 22, 2021
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@taiki-e Ping from triage. It seems the next step for this PR would be update the docs and switching this PR to S-waiting-on-review?

@JohnCSimon JohnCSimon added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Mar 29, 2021
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Closing this due to inactivity.

@Dylan-DPC-zz Dylan-DPC-zz added S-inactive Status: Inactive and waiting on the author. This is often applied to closed PRs. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Mar 29, 2021
@taiki-e taiki-e mentioned this pull request Jul 27, 2022
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