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Check stalled coroutine obligations eagerly #152327

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Merged
rust-bors merged 2 commits into from
Feb 9, 2026
Merged

Check stalled coroutine obligations eagerly #152327

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d8ff397
check stalled coroutine obligations eagerly
adwinwhite Feb 8, 2026
f248395
bless tests
adwinwhite Feb 8, 2026
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5 changes: 5 additions & 0 deletions compiler/rustc_borrowck/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -121,6 +121,11 @@ fn mir_borrowck(
let (input_body, _) = tcx.mir_promoted(def);
debug!("run query mir_borrowck: {}", tcx.def_path_str(def));

// We should eagerly check stalled coroutine obligations from HIR typeck.
// Not doing so leads to silent normalization failures later, which will
// fail to register opaque types in the next solver.
tcx.check_coroutine_obligations(def)?;
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@nnethercote nnethercote Mar 4, 2026

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A question: would it be ok to use tcx.ensure_ok().check_coroutine_obligations(...) here? Or is that what the comment is explaining?

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@adwinwhite adwinwhite Mar 4, 2026 •
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IIRC, We care about the returned result here so we can't use ensure_ok.
Or am I misunderstanding the behavior of ensure_ok?

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@nnethercote nnethercote Mar 4, 2026 •
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It's confusing: ensure_ok generally means "ignore the return value". However, the check_coroutine_obligations query is marked with the return_result_from_ensure_ok modifier. Which means that using ensure_ok will return Result<(), ErrorGuaranteed>. See this function for full details, especially the comment at the bottom.

As per that comment, using ensure_ok here means you sometimes get a slight optimization where we can skip the query when doing incremental compilation. My guess is that this would be ok, i.e. ensure_ok would work here.

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@nnethercote nnethercote Mar 4, 2026

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The ui and incremental tests pass if I insert the ensure_ok.

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@adwinwhite adwinwhite Mar 4, 2026

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In that case, yeah, we should use ensure_ok.
Thank you for catching this!

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@nnethercote nnethercote Mar 4, 2026

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I am working on a PR to improve ensure_ok. I will include this change as part of it.

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@nnethercote nnethercote Mar 4, 2026

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#153383 is the PR.


let input_body: &Body<'_> = &input_body.borrow();
if let Some(guar) = input_body.tainted_by_errors {
debug!("Skipping borrowck because of tainted body");
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18 changes: 7 additions & 11 deletions compiler/rustc_interface/src/passes.rs
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Expand Up @@ -1116,18 +1116,14 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
{
tcx.ensure_ok().mir_drops_elaborated_and_const_checked(def_id);
}
if tcx.is_coroutine(def_id.to_def_id()) {
tcx.ensure_ok().mir_coroutine_witnesses(def_id);
let _ = tcx.ensure_ok().check_coroutine_obligations(
tcx.typeck_root_def_id(def_id.to_def_id()).expect_local(),
if tcx.is_coroutine(def_id.to_def_id())
&& (!tcx.is_async_drop_in_place_coroutine(def_id.to_def_id()))
{
// Eagerly check the unsubstituted layout for cycles.
tcx.ensure_ok().layout_of(
ty::TypingEnv::post_analysis(tcx, def_id.to_def_id())
.as_query_input(tcx.type_of(def_id).instantiate_identity()),
);
if !tcx.is_async_drop_in_place_coroutine(def_id.to_def_id()) {
// Eagerly check the unsubstituted layout for cycles.
tcx.ensure_ok().layout_of(
ty::TypingEnv::post_analysis(tcx, def_id.to_def_id())
.as_query_input(tcx.type_of(def_id).instantiate_identity()),
);
}
}
});
});
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