libcore: Add `iter::from_generator` which is like `iter::from_fn`, but for coroutines instead of functions #96298

petrochenkov · 2022-04-21T21:20:01Z

An equally useful little helper.

I didn't follow any of the async-wg work, so I don't know why something like this wasn't added before.

rust-highfive · 2022-04-21T21:20:04Z

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 r? rust-lang/libs-api @rustbot label +T-libs-api -T-libs to request review from a libs-api team reviewer. 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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rust-highfive · 2022-04-21T21:20:05Z

r? @m-ou-se

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

library/core/src/iter/mod.rs

library/core/src/iter/sources.rs

library/core/tests/iter/sources.rs

clarfonthey · 2022-04-23T11:19:02Z

library/core/src/iter/sources/from_generator.rs

+/// [`iter::from_fn`]: crate::iter::from_fn
+#[inline]
+#[unstable(feature = "iter_from_generator", issue = "none", reason = "generators are unstable")]
+pub fn from_generator<G: Generator<Return = ()> + Unpin>(


It might be reasonable to also add a version that accepts a Pin<&mut G>, since that way immovable generators can be used as well.

I'm intrigued if there's a way to support both from the same function (is a Pin<&mut Generator<Return = ()>>: Generator<Return = ()> + Unpin?)

Either way, I think we can add that on a follow up PR.

I'm not quite sure what you mean. Right now there isn't an easy way to accept both direct mutable references and pinned ones, but that would be a lovely thing.

I'm just wondering what changes we could make so that Pin<&mut Generator<Return = ()>> can satisfy Generator<Return = ()> + Unpin, making this function work for both versions.

Oh! Now I understand, I think. That's actually a good question...

Pretty sure that's already the case for Future (yup) so it shouldn't be hard to do it for Generator.

Wait, no, it has that already

clarfonthey · 2022-04-23T11:22:22Z

The main cases I've seen of this pattern in the wild have been via the propane crate which mostly provides exactly what this does except via a macro instead. Not sure if there are more recent uses that folks can point to, though.

estebank

I'm r=me after addressing @jyn514's nitpicks. If we ever stabilize generators this API will likely be either redundant or changed, but while the whole feature is unstable, having these kind of affordances is important.

…t for coroutines instead of functions

petrochenkov · 2022-05-26T22:54:07Z

@bors r=estebank

bors · 2022-05-26T22:54:08Z

📌 Commit 5bf23f6 has been approved by estebank

bors · 2022-05-27T01:01:18Z

⌛ Testing commit 5bf23f6 with merge 4f68efa...

bors · 2022-05-27T03:26:58Z

☀️ Test successful - checks-actions
Approved by: estebank
Pushing 4f68efa to master...

rust-timer · 2022-05-27T04:44:48Z

Finished benchmarking commit (4f68efa): comparison url.

Instruction count

Primary benchmarks: no relevant changes found
Secondary benchmarks: 🎉 relevant improvement found

	mean¹	max	count²
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	-0.9%	-0.9%	1
All 😿🎉 (primary)	N/A	N/A	0

Max RSS (memory usage)

Results

Primary benchmarks: no relevant changes found
Secondary benchmarks: mixed results

	mean¹	max	count²
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	1.5%	1.8%	2
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	-1.6%	-1.6%	1
All 😿🎉 (primary)	N/A	N/A	0

Cycles

Results

Primary benchmarks: 😿 relevant regression found
Secondary benchmarks: no relevant changes found

	mean¹	max	count²
Regressions 😿 (primary)	2.7%	2.7%	1
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	N/A	N/A	0
All 😿🎉 (primary)	2.7%	2.7%	1

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

the arithmetic mean of the percent change ↩ ↩² ↩³
number of relevant changes ↩ ↩² ↩³

rust-highfive assigned m-ou-se Apr 21, 2022

rustbot added T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Apr 21, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 21, 2022

petrochenkov added T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. and removed T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Apr 21, 2022

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jyn514 approved these changes Apr 21, 2022

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estebank approved these changes May 26, 2022

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petrochenkov 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 26, 2022

libcore: Add iter::from_generator which is like iter::from_fn, bu…

5bf23f6

…t for coroutines instead of functions

petrochenkov force-pushed the fromgen branch from 1d4d001 to 5bf23f6 Compare May 26, 2022 22:52

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 26, 2022

bors added the merged-by-bors This PR was explicitly merged by bors. label May 27, 2022

bors merged commit 4f68efa into rust-lang:master May 27, 2022

rustbot added this to the 1.63.0 milestone May 27, 2022

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libcore: Add `iter::from_generator` which is like `iter::from_fn`, but for coroutines instead of functions #96298

libcore: Add `iter::from_generator` which is like `iter::from_fn`, but for coroutines instead of functions #96298

petrochenkov commented Apr 21, 2022 •

edited

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clarfonthey Apr 23, 2022

estebank May 26, 2022

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clarfonthey May 26, 2022

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rust-timer commented May 27, 2022

libcore: Add iter::from_generator which is like iter::from_fn, but for coroutines instead of functions #96298

libcore: Add iter::from_generator which is like iter::from_fn, but for coroutines instead of functions #96298

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rust-timer commented May 27, 2022

Footnotes

libcore: Add `iter::from_generator` which is like `iter::from_fn`, but for coroutines instead of functions #96298

libcore: Add `iter::from_generator` which is like `iter::from_fn`, but for coroutines instead of functions #96298

petrochenkov commented Apr 21, 2022 •

edited

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