Implement <Rc>::downcast by bluss · Pull Request #44273 · rust-lang/rust (original) (raw)
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- Implement
<Rc<Any>>::downcast::<T>- New unstable method. Works just like Box, but for Rc.
- Any has two cases for its methods: Any and Any + Send; Rc is never Send, so that case is skipped for Rc.
- Motivation for being a method with self is to match Box and there is no user-supplied type; the inner type is Any and downcast does not conflict with any method of Any.
- Arc was skipped because Any itself has no downcast for the case that makes most sense: Any + Send + Sync
r? @sfackler
(rust_highfive has picked a reviewer for you, use r? to override)
I'll probably revise this -- the pointer math in from_raw does not optimize out as it should
Arc is skipped because Any itself has no downcast for the case that makes most sense: Any + Send + Sync
Why we don't implement downcast for Any + Send + Sync? Other than it isn't terribly necessary.
Implement downcast the like it exists for Box.
The implementation avoids using into_raw/from_raw, because the pointer arithmetic which should cancel does not seem to optimize out at the moment.
Since Rc is never Send, only Rc and not Rc<Any + Send> implements downcast.
Implement <Rc>::downcast and generalize Rc::into_raw Implement <Rc>::downcast
I pushed a new version with a more direct implementation, because the pointer arithmetic of using into_raw/from_raw did not optimize out. (playground demo for that)
@kennytm I'm not sure, there are only four combinations of Any and Send, Sync, so it's simple to cover them all, but a bit confusing in the API doc.
Relevant to the library API team, which will review and decide on the PR/issue.
label
This seems reasonable to me.
@rfcbot fcp merge
Team member @sfackler has proposed to merge this. The next step is review by the rest of the tagged teams:
No concerns currently listed.
Once these reviewers reach consensus, 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!
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🔔 This is now entering its final comment period, as per the review above. 🔔
📌 Commit 758a0ce has been approved by alexcrichton
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- label).
labels
@bors: r-
oh actually, @bluss mind filing a tracking issue for this and updating the PR with that number?
Sure, updated with tracking issue #44608
📌 Commit 3a39d95 has been approved by alexcrichton
alexcrichton added a commit to alexcrichton/rust that referenced this pull request
Implement <Rc>::downcast
- Implement
<Rc<Any>>::downcast::<T>- New unstable method. Works just like Box<Any>, but for Rc.
- Any has two cases for its methods: Any and Any + Send; Rc is never Send, so that case is skipped for Rc.
- Motivation for being a method with self is to match Box and there is no user-supplied type; the inner type is Any and downcast does not conflict with any method of Any.
- Arc was skipped because Any itself has no downcast for the case that makes most sense: Any + Send + Sync
frewsxcv added a commit to frewsxcv/rust that referenced this pull request
Implement <Rc>::downcast
- Implement
<Rc<Any>>::downcast::<T>- New unstable method. Works just like Box<Any>, but for Rc.
- Any has two cases for its methods: Any and Any + Send; Rc is never Send, so that case is skipped for Rc.
- Motivation for being a method with self is to match Box and there is no user-supplied type; the inner type is Any and downcast does not conflict with any method of Any.
- Arc was skipped because Any itself has no downcast for the case that makes most sense: Any + Send + Sync
alexcrichton added a commit to alexcrichton/rust that referenced this pull request
Implement <Rc>::downcast
- Implement
<Rc<Any>>::downcast::<T>- New unstable method. Works just like Box<Any>, but for Rc.
- Any has two cases for its methods: Any and Any + Send; Rc is never Send, so that case is skipped for Rc.
- Motivation for being a method with self is to match Box and there is no user-supplied type; the inner type is Any and downcast does not conflict with any method of Any.
- Arc was skipped because Any itself has no downcast for the case that makes most sense: Any + Send + Sync
bors added a commit that referenced this pull request
Rollup of 19 pull requests
- Successful merges: #44273, #44356, #44395, #44531, #44537, #44542, #44560, #44567, #44574, #44577, #44586, #44589, #44590, #44593, #44598, #44606, #44609, #44616, #44631
- Failed merges:
Labels
In the final comment period and will be merged soon unless new substantive objections are raised.
Status: Waiting on bors to run and complete tests. Bors will change the label on completion.
Relevant to the library API team, which will review and decide on the PR/issue.