Suggest using `Arc` on `!Send`/`!Sync` types #88936

estebank · 2021-09-14T15:48:46Z

No description provided.

rust-highfive · 2021-09-14T15:48:50Z

(rust-highfive has picked a reviewer for you, use r? to override)

m-ou-se · 2021-09-21T08:34:51Z

src/test/ui/associated-type-bounds/bad-bounds-on-assoc-in-trait.stderr

-LL | |     // Empty
-LL | | }
-   | |_^ required by this bound in `Sync`
+   = note: consider using `std::sync::Arc<<<Self as Case1>::C as Iterator>::Item>`; for more information visit <https://doc.rust-lang.org/book/ch16-03-shared-state.html>


This now seems to suggest to use Arc<..::Item> instead of ..::Item. It might be useful to say consider using Arc instead of Rc: ....

But That's exactly what this is suggesting: we didn't have an Rc here. Ideally we should be able to tell what context this error is being emitted on, but sadly rustc_on_unimplemented doesn't have that filtering today.

yaahc · 2021-10-04T22:06:20Z

r? rust-lang/compiler

nagisa · 2021-10-08T17:16:25Z

library/core/src/marker.rs

@@ -32,8 +32,11 @@ use crate::hash::Hasher;
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "send_trait")]
 #[rustc_on_unimplemented(
+    on(_Self = "std::rc::Rc<T>", note = "use `std::sync::Arc` instead"),


Use of Arc is not always applicable, as both Send and Sync impls for Arc<T> require T: Send + Sync. Unless we can verify T bounds here, I don't think this on clause adds any more clarity over the default note?

Thats fair, but was concerned the default would be too verbose for a case where we could be more straightforward. I can change it.

Well, we can always change this later too. r=me if you don't want to change it.

nagisa · 2021-10-08T17:19:45Z

library/core/src/marker.rs

    message = "`{Self}` cannot be sent between threads safely",
-    label = "`{Self}` cannot be sent between threads safely"
+    label = "`{Self}` cannot be sent between threads safely",


Out of curiosity, what's the effect of this label clause here? I was thinking that this text would appear near the span underline, but tests indicate that nothing really changed in that particular aspect, at least.

It's the primary span text.

nagisa · 2021-10-17T09:40:17Z

@bors r+

bors · 2021-10-17T09:40:19Z

📌 Commit e2cffd73c83c54c629ed88b30bb7f8a486d0b1ec has been approved by nagisa

bors · 2021-10-17T12:28:01Z

⌛ Testing commit e2cffd73c83c54c629ed88b30bb7f8a486d0b1ec with merge e5fb2513a52b92052d5e17ff7414a5e291ba205d...

bors · 2021-10-17T12:33:07Z

💔 Test failed - checks-actions

estebank · 2021-11-23T20:10:54Z

@bors r=nagisa

bors · 2021-11-23T20:10:56Z

📌 Commit afd717c52628de0c39329c648e56abecf28b9e8f has been approved by nagisa

bors · 2022-03-05T10:39:24Z

🔒 Merge conflict

This pull request and the master branch diverged in a way that cannot be automatically merged. Please rebase on top of the latest master branch, and let the reviewer approve again.

How do I rebase?

Assuming self is your fork and upstream is this repository, you can resolve the conflict following these steps:

git checkout send-sync (switch to your branch)
git fetch upstream master (retrieve the latest master)
git rebase upstream/master -p (rebase on top of it)
Follow the on-screen instruction to resolve conflicts (check git status if you got lost).
git push self send-sync --force-with-lease (update this PR)

You may also read Git Rebasing to Resolve Conflicts by Drew Blessing for a short tutorial.

Please avoid the "Resolve conflicts" button on GitHub. It uses git merge instead of git rebase which makes the PR commit history more difficult to read.

Sometimes step 4 will complete without asking for resolution. This is usually due to difference between how Cargo.lock conflict is handled during merge and rebase. This is normal, and you should still perform step 5 to update this PR.

Error message

Auto-merging src/test/ui/traits/inductive-overflow/two-traits.stderr
Auto-merging src/test/ui/issues/issue-7364.stderr
Auto-merging src/test/ui/issues/issue-17718-static-sync.stderr
Auto-merging src/test/ui/issues/issue-16538.thir.stderr
CONFLICT (content): Merge conflict in src/test/ui/issues/issue-16538.thir.stderr
Auto-merging src/test/ui/issues/issue-16538.mir.stderr
CONFLICT (content): Merge conflict in src/test/ui/issues/issue-16538.mir.stderr
Auto-merging src/test/ui/impl-trait/auto-trait-leak2.stderr
CONFLICT (content): Merge conflict in src/test/ui/impl-trait/auto-trait-leak2.stderr
Auto-merging src/test/ui/generator/print/generator-print-verbose-1.stderr
Auto-merging src/test/ui/generator/issue-68112.stderr
Auto-merging src/test/ui/async-await/issues/issue-65436-raw-ptr-not-send.stderr
CONFLICT (content): Merge conflict in src/test/ui/async-await/issues/issue-65436-raw-ptr-not-send.stderr
Auto-merging src/test/ui/async-await/issue-71137.stderr
Auto-merging src/test/ui/async-await/issue-70935-complex-spans.stderr
Auto-merging src/test/ui/async-await/issue-68112.stderr
Auto-merging src/test/ui/async-await/issue-67252-unnamed-future.stderr
CONFLICT (content): Merge conflict in src/test/ui/async-await/issue-67252-unnamed-future.stderr
Auto-merging src/test/ui/async-await/issue-64130-non-send-future-diags.stderr
Auto-merging src/test/ui/async-await/issue-64130-4-async-move.stderr
Auto-merging src/test/ui/async-await/issue-64130-2-send.stderr
Auto-merging src/test/ui/async-await/issue-64130-1-sync.stderr
Auto-merging src/test/ui/async-await/async-fn-nonsend.stderr
CONFLICT (content): Merge conflict in src/test/ui/async-await/async-fn-nonsend.stderr
Auto-merging src/test/ui/associated-type-bounds/bad-bounds-on-assoc-in-trait.stderr
Auto-merging compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
Automatic merge failed; fix conflicts and then commit the result.

bors · 2022-03-14T11:04:41Z

🔒 Merge conflict

This pull request and the master branch diverged in a way that cannot be automatically merged. Please rebase on top of the latest master branch, and let the reviewer approve again.

How do I rebase?

Assuming self is your fork and upstream is this repository, you can resolve the conflict following these steps:

git checkout send-sync (switch to your branch)
git fetch upstream master (retrieve the latest master)
git rebase upstream/master -p (rebase on top of it)
Follow the on-screen instruction to resolve conflicts (check git status if you got lost).
git push self send-sync --force-with-lease (update this PR)

You may also read Git Rebasing to Resolve Conflicts by Drew Blessing for a short tutorial.

Please avoid the "Resolve conflicts" button on GitHub. It uses git merge instead of git rebase which makes the PR commit history more difficult to read.

Sometimes step 4 will complete without asking for resolution. This is usually due to difference between how Cargo.lock conflict is handled during merge and rebase. This is normal, and you should still perform step 5 to update this PR.

Error message

Auto-merging src/test/ui/traits/inductive-overflow/two-traits.stderr
Auto-merging src/test/ui/issues/issue-7364.stderr
Auto-merging src/test/ui/issues/issue-17718-static-sync.stderr
Auto-merging src/test/ui/issues/issue-16538.thir.stderr
CONFLICT (content): Merge conflict in src/test/ui/issues/issue-16538.thir.stderr
Auto-merging src/test/ui/issues/issue-16538.mir.stderr
CONFLICT (content): Merge conflict in src/test/ui/issues/issue-16538.mir.stderr
Auto-merging src/test/ui/impl-trait/auto-trait-leak2.stderr
CONFLICT (content): Merge conflict in src/test/ui/impl-trait/auto-trait-leak2.stderr
Auto-merging src/test/ui/generator/print/generator-print-verbose-1.stderr
Auto-merging src/test/ui/generator/issue-68112.stderr
Auto-merging src/test/ui/async-await/issues/issue-65436-raw-ptr-not-send.stderr
CONFLICT (content): Merge conflict in src/test/ui/async-await/issues/issue-65436-raw-ptr-not-send.stderr
Auto-merging src/test/ui/async-await/issue-71137.stderr
Auto-merging src/test/ui/async-await/issue-70935-complex-spans.stderr
Auto-merging src/test/ui/async-await/issue-68112.stderr
Auto-merging src/test/ui/async-await/issue-67252-unnamed-future.stderr
CONFLICT (content): Merge conflict in src/test/ui/async-await/issue-67252-unnamed-future.stderr
Auto-merging src/test/ui/async-await/issue-64130-non-send-future-diags.stderr
Auto-merging src/test/ui/async-await/issue-64130-4-async-move.stderr
Auto-merging src/test/ui/async-await/issue-64130-2-send.stderr
Auto-merging src/test/ui/async-await/issue-64130-1-sync.stderr
Auto-merging src/test/ui/async-await/async-fn-nonsend.stderr
CONFLICT (content): Merge conflict in src/test/ui/async-await/async-fn-nonsend.stderr
Auto-merging src/test/ui/associated-type-bounds/bad-bounds-on-assoc-in-trait.stderr
Auto-merging library/core/src/marker.rs
Auto-merging compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
Automatic merge failed; fix conflicts and then commit the result.

bors · 2022-03-26T14:45:55Z

🔒 Merge conflict

This pull request and the master branch diverged in a way that cannot be automatically merged. Please rebase on top of the latest master branch, and let the reviewer approve again.

How do I rebase?

Assuming self is your fork and upstream is this repository, you can resolve the conflict following these steps:

git checkout send-sync (switch to your branch)
git fetch upstream master (retrieve the latest master)
git rebase upstream/master -p (rebase on top of it)
Follow the on-screen instruction to resolve conflicts (check git status if you got lost).
git push self send-sync --force-with-lease (update this PR)

You may also read Git Rebasing to Resolve Conflicts by Drew Blessing for a short tutorial.

Please avoid the "Resolve conflicts" button on GitHub. It uses git merge instead of git rebase which makes the PR commit history more difficult to read.

Sometimes step 4 will complete without asking for resolution. This is usually due to difference between how Cargo.lock conflict is handled during merge and rebase. This is normal, and you should still perform step 5 to update this PR.

Error message

Auto-merging src/test/ui/traits/inductive-overflow/two-traits.stderr
Auto-merging src/test/ui/traits/alias/cross-crate.stderr
CONFLICT (content): Merge conflict in src/test/ui/traits/alias/cross-crate.stderr
Auto-merging src/test/ui/issues/issue-7364.stderr
Auto-merging src/test/ui/issues/issue-17718-static-sync.stderr
Auto-merging src/test/ui/issues/issue-16538.thir.stderr
CONFLICT (content): Merge conflict in src/test/ui/issues/issue-16538.thir.stderr
Auto-merging src/test/ui/issues/issue-16538.mir.stderr
CONFLICT (content): Merge conflict in src/test/ui/issues/issue-16538.mir.stderr
Auto-merging src/test/ui/impl-trait/auto-trait-leak2.stderr
CONFLICT (content): Merge conflict in src/test/ui/impl-trait/auto-trait-leak2.stderr
Auto-merging src/test/ui/generator/print/generator-print-verbose-1.stderr
Auto-merging src/test/ui/generator/issue-68112.stderr
Auto-merging src/test/ui/async-await/issues/issue-65436-raw-ptr-not-send.stderr
Auto-merging src/test/ui/async-await/issue-71137.stderr
Auto-merging src/test/ui/async-await/issue-70935-complex-spans.stderr
Auto-merging src/test/ui/async-await/issue-67252-unnamed-future.stderr
Auto-merging src/test/ui/async-await/issue-64130-non-send-future-diags.stderr
Auto-merging src/test/ui/async-await/issue-64130-4-async-move.stderr
Auto-merging src/test/ui/async-await/issue-64130-2-send.stderr
Auto-merging src/test/ui/async-await/issue-64130-1-sync.stderr
Auto-merging src/test/ui/async-await/async-fn-nonsend.stderr
CONFLICT (content): Merge conflict in src/test/ui/async-await/async-fn-nonsend.stderr
Auto-merging src/test/ui/associated-type-bounds/bad-bounds-on-assoc-in-trait.stderr
Auto-merging library/core/src/marker.rs
Auto-merging compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
Automatic merge failed; fix conflicts and then commit the result.

compiler-errors · 2022-05-07T18:11:39Z

A bors sync made this re-approved, sorry hehe

@bors r-

Dylan-DPC · 2022-11-21T15:39:50Z

Closing this as it is inactive

estebank · 2023-08-09T15:02:00Z

Squashed, rebased on top of current main and re-blessed the tests. No other changes since the prior approval.

@bors r=nagisa

bors · 2023-08-09T15:02:07Z

📌 Commit 9de1a47 has been approved by nagisa

It is now in the queue for this repository.

bors · 2023-08-09T15:35:54Z

⌛ Testing commit 9de1a47 with merge 27a43f0...

compiler-errors · 2023-08-09T16:14:20Z

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -2743,6 +2743,12 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
            }
            ObligationCauseCode::BindingObligation(item_def_id, span)
            | ObligationCauseCode::ExprBindingObligation(item_def_id, span, ..) => {
+                if self.tcx.is_diagnostic_item(sym::Send, item_def_id)


why isn't this commented? seems like something that could use a justification

I'll add a comment.

bors · 2023-08-09T18:09:59Z

☀️ Test successful - checks-actions
Approved by: nagisa
Pushing 27a43f0 to master...

bors · 2023-08-09T18:10:00Z

☀️ Test successful - checks-actions
Approved by: nagisa
Pushing 27a43f0 to master...

rust-timer · 2023-08-09T20:35:45Z

Finished benchmarking commit (27a43f0): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.7%	[1.2%, 2.1%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 632.651s -> 632.289s (-0.06%)

Revert "Suggest using `Arc` on `!Send`/`!Sync` types" Closes rust-lang#114687. This is a clean revert of rust-lang#88936 + rust-lang#115210. The suggestion to Arc\<{Self}\> when Self does not implement Send is *always* wrong. rust-lang#114842 is considering a way to make a more refined suggestion.

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Dylan-DPC closed this Nov 21, 2022

estebank reopened this Aug 9, 2023

Suggest using Arc on !Send/!Sync types

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Enable -Zdrop-tracking-mir by default #107421

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Introduce more fine-grained borrowed locals analysis for generators #112050

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Stop considering moved-out locals when computing auto traits for generators #112279

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dtolnay mentioned this pull request Aug 10, 2023

Suggestion to use Arc<T> is too indiscriminate #114687

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dtolnay mentioned this pull request Aug 28, 2023

Revert "Suggest using Arc on !Send/!Sync types" #115311

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Suggest using `Arc` on `!Send`/`!Sync` types #88936

Suggest using `Arc` on `!Send`/`!Sync` types #88936

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Suggest using Arc on !Send/!Sync types #88936

Suggest using Arc on !Send/!Sync types #88936

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Suggest using `Arc` on `!Send`/`!Sync` types #88936

Suggest using `Arc` on `!Send`/`!Sync` types #88936

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