Skip to content

Make inline attributes apply to the generated poll in async fn - #149245

Open
xacrimon wants to merge 1 commit into
rust-lang:mainfrom
xacrimon:acrimon/async-fn-inline-attr
Open

Make inline attributes apply to the generated poll in async fn#149245
xacrimon wants to merge 1 commit into
rust-lang:mainfrom
xacrimon:acrimon/async-fn-inline-attr

Conversation

@xacrimon

@xacrimon xacrimon commented Nov 23, 2025 •
edited by JonathanBrouwer
Loading

Copy link
Copy Markdown
Contributor

This PR adds lowering code (similar to how track_caller forwarding works) to async fn items and async || closures such that any inline attributes put on them are inherited by the generated coroutine (corresponding to the poll() implementation) and are not applied to the outer function. This behavior matches the accepted FCP in the first linked issue.

Code like the following now correctly codegen 3 functions

  • async_fn_test::consumer
  • async_fn_test::hi::{closure#0}
  • core::ptr::drop_in_place::<async_fn_test::hi::{closure#0}>
#[inline(never)]
pub async fn hi() -> i32 {
    1337
}

pub fn consumer(cx: &mut Context<'_>) -> Option<i32> {
    let fut = hi();
    let pinned = pin!(fut);
    match pinned.poll(cx) {
        Poll::Ready(value) => Some(value),
        Poll::Pending => None,
    }
}

Fixes #129347 and fixes #106765.

This has already been FCP'ed here: #129347

@rustbot rustbot added A-attributes Area: Attributes (`#[…]`, `#![…]`) S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Nov 23, 2025
@rustbot

rustbot commented Nov 23, 2025

Copy link
Copy Markdown
Collaborator

r? @JonathanBrouwer

rustbot has assigned @JonathanBrouwer.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

@rustbot

This comment has been minimized.

Sign in to view
@xacrimon
xacrimon force-pushed the acrimon/async-fn-inline-attr branch from 46d6c3e to d89022a Compare November 23, 2025 20:55
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@xacrimon
xacrimon force-pushed the acrimon/async-fn-inline-attr branch 5 times, most recently from 9478bfd to fa35f7b Compare November 23, 2025 23:25
@rust-log-analyzer

This comment has been minimized.

Sign in to view
@JonathanBrouwer

JonathanBrouwer commented Nov 25, 2025

Copy link
Copy Markdown
Member

@rustbot author
CI is failing

@rustbot rustbot 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 Nov 25, 2025
@rustbot

rustbot commented Nov 25, 2025

Copy link
Copy Markdown
Collaborator

Reminder, once the PR becomes ready for a review, use @rustbot ready.

@bors

bors commented Dec 11, 2025

Copy link
Copy Markdown
Collaborator

☔ The latest upstream changes (presumably #149853) made this pull request unmergeable. Please resolve the merge conflicts.

@rust-bors

rust-bors Bot commented Jan 2, 2026

Copy link
Copy Markdown
Contributor

☔ The latest upstream changes made this pull request unmergeable. Please resolve the merge conflicts.

@Mark-Simulacrum Mark-Simulacrum added the relnotes Marks issues that should be documented in the release notes of the next release. label Jan 25, 2026
@rustbot rustbot mentioned this pull request Jan 25, 2026
Open
@Enselic

Enselic commented Mar 20, 2026

Copy link
Copy Markdown
Member

Triage: Are you still working on this @xacrimon?

@xacrimon
xacrimon force-pushed the acrimon/async-fn-inline-attr branch from fa35f7b to 7054408 Compare April 5, 2026 16:59
@rustbot

This comment has been minimized.

Sign in to view
@rust-bors

This comment has been minimized.

Sign in to view
@Dylan-DPC Dylan-DPC added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 16, 2026
JonathanBrouwer
JonathanBrouwer requested changes Jun 21, 2026
View reviewed changes
Comment thread compiler/rustc_ast_lowering/src/expr.rs Outdated
Comment thread compiler/rustc_ast_lowering/src/expr.rs Outdated
Comment thread compiler/rustc_ast_lowering/src/expr.rs Outdated
);

this.maybe_forward_track_caller(body.span, closure_hir_id, expr.hir_id);
this.forward_inline(body.span, closure_hir_id, expr.hir_id);

@JonathanBrouwer JonathanBrouwer Jun 21, 2026 •
edited by rustbot
Loading

Copy link
Copy Markdown
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Could you add some tests for this feature?

View changes since the review

@JonathanBrouwer JonathanBrouwer Jun 21, 2026 •
edited
Loading

Copy link
Copy Markdown
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

From the lang team decision:

We talked about this in the lang call today. We want attributes like this to apply to "where the code is", i.e. to the poll function in this case. The wrapper function, on the other hand, should always be inlined.

Make sure your tests cover this.
I suspect the wrapper function is already marked as inline somewhere, if it is not could you or someone else open a separate PR that does this?

@xacrimon xacrimon Sep 26, 2026 •
edited
Loading

Copy link
Copy Markdown
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

The wrapper function is automatically marked as inline by the automating inlining of small functions in every case I tested, since it just returns a hardcoded value.

@rustbot rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 21, 2026
@rustbot rustbot added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jun 21, 2026
@JonathanBrouwer

JonathanBrouwer commented Jun 21, 2026 •
edited
Loading

Copy link
Copy Markdown
Member

Sorry for taking so long to review this PR! This PR fell of my radar, thanks @Dylan-DPC for fixing up the label so I saw it again

@xacrimon
inline and cold attributes on async fn and async closures affect the …
0c5f331 
…poll impl instead of the desugared creator function.
@xacrimon
xacrimon force-pushed the acrimon/async-fn-inline-attr branch from 7054408 to 0c5f331 Compare September 26, 2026 19:22
@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Sep 26, 2026
@rustbot

rustbot commented Sep 26, 2026

Copy link
Copy Markdown
Collaborator

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

@xacrimon

xacrimon commented Sep 26, 2026

Copy link
Copy Markdown
Contributor Author

@Enselic yep, I was too busy to work on this for an extended amount of time. but now I have time again and intend to see it merged.

@xacrimon

xacrimon commented Sep 26, 2026 •
edited
Loading

Copy link
Copy Markdown
Contributor Author

I have now rebased the PR onto the current main, this required a fundemental approach change due some issues I found with lints being incorrectly applied after modifying the HIR in addition to the area of the codebase where I made my change being largely rewritten in the meantime in a way that wasn't amenable to the previous approach.

We now handle this in a later step in IR gen, which after talking to some people on Zulip, seems like the better place to do it now.

@xacrimon

xacrimon commented Sep 26, 2026

Copy link
Copy Markdown
Contributor Author

@rustbot ready

@xacrimon

xacrimon commented Sep 26, 2026

Copy link
Copy Markdown
Contributor Author

since so much time has passed, do you still want to review this or should I reassign? @JonathanBrouwer

This branch has not been deployed

No deployments
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@JonathanBrouwer JonathanBrouwer Awaiting requested review from JonathanBrouwer

Requested changes must be addressed to merge this pull request.

Assignees

@JonathanBrouwer JonathanBrouwer

Labels

A-attributes Area: Attributes (`#[…]`, `#![…]`) relnotes Marks issues that should be documented in the release notes of the next release. S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

Projects

None yet

Milestone

No milestone

Development

Successfully merging this pull request may close these issues.

#[inline(never)] does not work for async functions #[inline(never)] does not work for async fn

8 participants

@xacrimon @rustbot @rust-log-analyzer @JonathanBrouwer @bors @Enselic @Mark-Simulacrum @Dylan-DPC