Arc downcast #50836

jsgf · 2018-05-17T15:33:13Z

Implement downcast for Arc<Any + Send + Sync> as part of #44608, and gated by the same rc_downcast feature.

This PR is mostly lightly-edited cut'n'paste.

This has two additional changes:

The downcast implementation needs Any + Send + Sync implementations for is and Debug, and I added downcast_ref and downcast_mut for completeness/consistency. (Can these be insta-stabilized?)
At @SimonSapin's suggestion, I converted Arc and Rc to use NonNull::cast to avoid an unsafe block in each which tidied things up nicely.

pietroalbini · 2018-05-17T16:41:01Z

SimonSapin · 2018-05-17T21:05:08Z

Stability attributes on trait impls don’t really work, so those impls are effectively insta-stable if both the trait and type are stable.

Any + Send + Sync methods can be made unstable and on principle should, but since they’re identical to existing Any and Any + Send methods I’m ok with landing them as insta-stable.

In both cases though, the attribute should still be accurate and say since = "1.28.0". That probably requires having a different feature name, maybe any_send_sync_methods or something.

jsgf · 2018-05-17T23:08:16Z

OK, I made them

    #[stable(feature = "any_send_sync_methods", since = "1.28.0")]

SimonSapin · 2018-05-18T06:48:49Z

r=me on the diff. Let’s also get team sign off on insta-stable APIs:

impl Debug for Any + Send + Sync
<Any+Send+Sync>::is:<T: Any>(&self) -> bool
<Any+Send+Sync>::downcast_ref:<T: Any>(&self) -> Option<&T>
<Any+Send+Sync>::downcast_mut:<T: Any>(&mut self) -> Option<&mut T>

@rfcbot fcp merge

SimonSapin · 2018-05-18T06:51:31Z

@rfcbot fcp merge

rfcbot · 2018-05-18T06:51:32Z

Team member @SimonSapin has proposed to merge this. The next step is review by the rest of the tagged teams:

No concerns currently listed.

Once a majority of reviewers approve (and none object), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

burtonageo · 2018-05-18T20:39:28Z

src/liballoc/arc.rs

@@ -971,6 +972,44 @@ unsafe impl<#[may_dangle] T: ?Sized> Drop for Arc<T> {
    }
 }

+impl Arc<Any + Send + Sync> {
+    #[inline]


Attributes tend to go below doc comments

This is a copy of the corresponding code in Rc. I agree it looks strange.

rfcbot · 2018-05-26T09:41:51Z

🔔 This is now entering its final comment period, as per the review above. 🔔

SimonSapin · 2018-05-31T19:15:54Z

@bors r+

Thanks!

bors · 2018-05-31T19:15:55Z

📌 Commit f7d06f8 has been approved by SimonSapin

bors · 2018-05-31T19:53:20Z

🔒 Merge conflict

Implement `is`, `downcast_ref`, `downcast_mut` and `Debug` for `Any + Send + Sync`.

We only need to implement it for `Any + Send + Sync` because in practice that's the only useful combination for `Arc` and `Any`. Implementation for rust-lang#44608 under the `rc_downcast` feature.

This avoids an `unsafe` block in each case.

Make the Any+Send+Sync examples use the right trait bounds, and fix a small whitespace issue.

jsgf · 2018-05-31T22:10:25Z

I rebased onto current master (though I didn't need to resolve any conflicts).

SimonSapin · 2018-05-31T23:05:03Z

@bors r+

bors · 2018-05-31T23:05:04Z

📌 Commit 87c3d7b has been approved by SimonSapin

bors · 2018-06-01T01:09:31Z

⌛ Testing commit 87c3d7b with merge b7a9d4e...

@SimonSapin

Arc downcast Implement `downcast` for `Arc<Any + Send + Sync>` as part of #44608, and gated by the same `rc_downcast` feature. This PR is mostly lightly-edited cut'n'paste. This has two additional changes: - The `downcast` implementation needs `Any + Send + Sync` implementations for `is` and `Debug`, and I added `downcast_ref` and `downcast_mut` for completeness/consistency. (Can these be insta-stabilized?) - At @SimonSapin's suggestion, I converted `Arc` and `Rc` to use `NonNull::cast` to avoid an `unsafe` block in each which tidied things up nicely.

bors · 2018-06-01T03:24:42Z

☀️ Test successful - status-appveyor, status-travis
Approved by: SimonSapin
Pushing b7a9d4e to master...

pthariensflame · 2018-06-07T01:14:41Z

Should this be tagged relnotes?

pietroalbini · 2018-06-07T08:40:33Z

Yep, thanks @pthariensflame!

SimonSapin · 2018-06-07T08:48:18Z

For the Any + Send + Sync parts, yes. The Arc parts are still unstable.

jsgf force-pushed the arc-downcast branch from 3cbd5c9 to 9d83e05 Compare May 17, 2018 15:37

pietroalbini added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 17, 2018

rust-highfive assigned SimonSapin May 17, 2018

jsgf force-pushed the arc-downcast branch from 9d83e05 to c9b5dbf Compare May 17, 2018 23:03

SimonSapin added S-waiting-on-team Status: Awaiting decision from the relevant subteam (see the T-<team> label). and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels May 18, 2018

rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels May 18, 2018

jsgf force-pushed the arc-downcast branch 2 times, most recently from 082e2ba to f7d06f8 Compare May 18, 2018 15:26

burtonageo suggested changes May 18, 2018

View reviewed changes

rfcbot added final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. and removed proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. labels May 26, 2018

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-team Status: Awaiting decision from the relevant subteam (see the T-<team> label). labels May 31, 2018

bors 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-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels May 31, 2018

jsgf added 4 commits May 31, 2018 13:27

Add implementations for Any + Send + Sync

72433e1

Implement `is`, `downcast_ref`, `downcast_mut` and `Debug` for `Any + Send + Sync`.

Implement downcast for Arc<Any + Send + Sync>

37f5cf5

We only need to implement it for `Any + Send + Sync` because in practice that's the only useful combination for `Arc` and `Any`. Implementation for rust-lang#44608 under the `rc_downcast` feature.

Update Arc and Rc to use NonNull::cast to cast the inner pointers

0c7bf56

This avoids an `unsafe` block in each case.

Fix up Any doc examples

87c3d7b

Make the Any+Send+Sync examples use the right trait bounds, and fix a small whitespace issue.

jsgf force-pushed the arc-downcast branch from f7d06f8 to 87c3d7b Compare May 31, 2018 20:28

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 31, 2018

bors merged commit 87c3d7b into rust-lang:master Jun 1, 2018

rfcbot added finished-final-comment-period The final comment period is finished for this PR / Issue. and removed final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels Jun 5, 2018

SimonSapin mentioned this pull request Jun 6, 2018

Tracking issue for Rc::downcast (rc_downcast feature) #44608

Closed

jsgf deleted the arc-downcast branch June 7, 2018 01:45

pietroalbini added the relnotes Marks issues that should be documented in the release notes of the next release. label Jun 7, 2018

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Arc downcast #50836

Arc downcast #50836

jsgf commented May 17, 2018

pietroalbini commented May 17, 2018

SimonSapin commented May 17, 2018

jsgf commented May 17, 2018

SimonSapin commented May 18, 2018 •

edited

Loading

SimonSapin commented May 18, 2018

rfcbot commented May 18, 2018 •

edited by Kimundi

Loading

burtonageo May 18, 2018

jsgf May 18, 2018 •

edited

Loading

rfcbot commented May 26, 2018

SimonSapin commented May 31, 2018

bors commented May 31, 2018

bors commented May 31, 2018

jsgf commented May 31, 2018

SimonSapin commented May 31, 2018

bors commented May 31, 2018

bors commented Jun 1, 2018

bors commented Jun 1, 2018

pthariensflame commented Jun 7, 2018

pietroalbini commented Jun 7, 2018

SimonSapin commented Jun 7, 2018

Arc downcast #50836

Arc downcast #50836

Conversation

jsgf commented May 17, 2018

pietroalbini commented May 17, 2018

SimonSapin commented May 17, 2018

jsgf commented May 17, 2018

SimonSapin commented May 18, 2018 • edited Loading

SimonSapin commented May 18, 2018

rfcbot commented May 18, 2018 • edited by Kimundi Loading

burtonageo May 18, 2018

Choose a reason for hiding this comment

jsgf May 18, 2018 • edited Loading

Choose a reason for hiding this comment

rfcbot commented May 26, 2018

SimonSapin commented May 31, 2018

bors commented May 31, 2018

bors commented May 31, 2018

jsgf commented May 31, 2018

SimonSapin commented May 31, 2018

bors commented May 31, 2018

bors commented Jun 1, 2018

bors commented Jun 1, 2018

pthariensflame commented Jun 7, 2018

pietroalbini commented Jun 7, 2018

SimonSapin commented Jun 7, 2018

SimonSapin commented May 18, 2018 •

edited

Loading

rfcbot commented May 18, 2018 •

edited by Kimundi

Loading

jsgf May 18, 2018 •

edited

Loading