Remove unnecessary Send bound

[GilShoshan94]

Hi,

While working on a PR on Tokio, I took inspiration from the std channel mpsc and stumbled on a Send bound for a Error impl.

Tokio's maintainer @Darksonn pointed out to me that Error used to required the Send bound long time ago (here #23541).

In the meantime, the Send bound Error got removed (see #21312 and #23799).

So here a PR to removed this bound for SendError<T>, TrySendError<T> and SendTimeoutError<T>.

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @thomcc (or someone else) soon.

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[rustbot]

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

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• Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
• Changing public documentation in ways that create new stability guarantees
• Changing observable runtime behavior of library APIs

[thomcc]

This seems clearly worth doing, but since it's an insta-stable change to a public API, it needs libs-api sign-off (maybe FCP).

r? @dtolnay

[dtolnay]

@rust-lang/libs-api:
@rfcbot fcp merge

I agree with @thomcc that this is an obvious change.

Removes the T: Send constraint from these 2 stable Error impls:

• https://doc.rust-lang.org/1.69.0/std/sync/mpsc/struct.SendError.html#impl-Error-for-SendError%3CT%3E
• https://doc.rust-lang.org/1.69.0/std/sync/mpsc/enum.TrySendError.html#impl-Error-for-TrySendError%3CT%3E

This used to be necessary prior to #21312 / #23799 and the impls just haven't gotten updated since then.

[rfcbot]

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

• @Amanieu
• @BurntSushi
• @dtolnay
• @joshtriplett
• @m-ou-se

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), 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.

[rfcbot]

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

[dtolnay]

@bors r+

[bors]

📌 Commit af5de85 has been approved by dtolnay

It is now in the queue for this repository.

[bors]

⌛ Testing commit af5de85 with merge 3ea9ad5...

[bors]

☀️ Test successful - checks-actions
Approved by: dtolnay
Pushing 3ea9ad5 to master...

[rust-timer]

Finished benchmarking commit (3ea9ad5): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.6%	[1.6%, 1.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

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

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: 642.879s -> 641.794s (-0.17%)