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Improve the documentation for ManuallyDrop to resolve conflicting usage of terminology #71625

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merged 1 commit into from
May 16, 2020

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Diggsey
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@Diggsey Diggsey commented Apr 27, 2020

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r? @cramertj

(rust_highfive has picked a reviewer for you, use r? to override)

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 27, 2020
@Diggsey Diggsey force-pushed the improve-manually-drop-docs branch from 24cfd0c to 904a77c Compare April 27, 2020 22:49
@Diggsey Diggsey force-pushed the improve-manually-drop-docs branch 2 times, most recently from 72bdab5 to 34c5e0c Compare April 28, 2020 21:28
src/libcore/ptr/mod.rs Outdated Show resolved Hide resolved
@Diggsey Diggsey force-pushed the improve-manually-drop-docs branch from 34c5e0c to 241ab21 Compare April 29, 2020 19:12
@@ -112,11 +112,17 @@ mod mut_ptr;
/// as the compiler doesn't need to prove that it's sound to elide the
/// copy.
///
/// * It can be used to drop [pinned] data (pinned data must not be moved
/// before it is dropped).
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Suggested change
/// before it is dropped).
/// before it is dropped), except if `T` is `repr(packed).

I feel currently this reads a bit like a contradiction, where it says "can be used to drop pinned data (because in-place)" but later says "but fields of packed structs are not dropped in-place".

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AIUI, packed structs with destructors cannot be pinned to begin with, and packed structs without destructors are presumably safe to drop using this function anyway?

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They cannot be pinned precisely because of what this comment says. If someone tries anyway, this is the place where they are violating the rules. So this is the place where that should be mentioned.

The compiler won't stop you when you try to pin something packed.

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Fixed. I put the caveat before the part in brackets because I felt it was awkward to read otherwise.

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cramertj commented May 8, 2020

r? @RalfJung

@rust-highfive rust-highfive assigned RalfJung and unassigned cramertj May 8, 2020
@RalfJung RalfJung 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-review Status: Awaiting review from the assignee but also interested parties. labels May 9, 2020
@Diggsey Diggsey force-pushed the improve-manually-drop-docs branch from 241ab21 to d8a3e59 Compare May 15, 2020 18:48
@Diggsey Diggsey force-pushed the improve-manually-drop-docs branch from d8a3e59 to 7433c4d Compare May 15, 2020 18:53
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This looks great, thanks a lot. :)
@bors r+ rollup

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bors commented May 16, 2020

📌 Commit 7433c4d has been approved by RalfJung

@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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels May 16, 2020
@RalfJung RalfJung changed the title Improve the documentation for ManuallyDrop to resolve conflicting usa… Improve the documentation for ManuallyDrop to resolve conflicting usage of terminology May 16, 2020
bors added a commit to rust-lang-ci/rust that referenced this pull request May 16, 2020
Rollup of 7 pull requests

Successful merges:

 - rust-lang#71625 (Improve the documentation for ManuallyDrop to resolve conflicting usage of terminology)
 - rust-lang#71919 (Update transitive dependency to work towards removing syn <1.0 dep)
 - rust-lang#72166 (Simpler slice `Iterator` methods)
 - rust-lang#72216 (Remove `lang_items\(\).*\.unwrap\(\)`)
 - rust-lang#72230 (Updated documentation of Prefix::VerbatimDisk)
 - rust-lang#72234 (Implement Default for proc_macro::TokenStream)
 - rust-lang#72258 (Fix typo Arbintrary to Arbitrary)

Failed merges:

r? @ghost
@bors bors merged commit 9c32e7a into rust-lang:master May 16, 2020
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5 participants