Check stalled coroutine obligations eagerly by adwinwhite · Pull Request #152327 · rust-lang/rust

adwinwhite · 2026-02-08T09:15:28Z

Fixes #151322
Fixes #151323
Fixes #137916
Fixes #138274

The problem is that stalled coroutine obligations can't be satisifed so that they cause normalization to fail in mir_borrowck.
Thus, we failed to register any opaque to storage in the next solver.
I fix it by checking these obligations earlier in mir_borrowck.

r? @lcnr

adwinwhite · 2026-02-08T09:17:22Z

tests/ui/traits/next-solver/stalled-coroutine-obligations.stderr

+LL |     let foo: T = async { a };
+   |                          ^ has type `False` which does not implement `Valid`
+
+error[E0271]: type mismatch resolving `impl Future + Send == {async block@$DIR/stalled-coroutine-obligations.rs:40:9: 40:19}`


The diagnostics for #151323 code is bad because find_best_leaf_obligation doesn't really find the leaf obligation that failed.
BestObligation proof tree visitor is kinda complicated to understand. I plan to improve the diagnostics in a follow-up PR.

adwinwhite · 2026-02-08T09:20:34Z

tests/ui/coroutine/issue-105084.rs

@@ -36,7 +36,6 @@ fn main() {
    // one inside `g` and one inside `h`.
    // Proceed and drop `t` in `g`.
    Pin::new(&mut g).resume(());
-    //~^ ERROR borrow of moved value: `g`


Now that we check stalled_coroutine_obligations before actual borrowck, we won't have borrowck diagnostics if those obligations fail.
I hope this is okay since HIR typeck failure also causes us skipping borrowck.
And stalled_coroutine_obligations should belong to HIR typeck if not for query cycle issue.

adwinwhite · 2026-02-08T09:23:03Z

tests/ui/async-await/issue-70818.stderr

One less duplicate error.

adwinwhite · 2026-02-08T09:23:14Z

tests/ui/async-await/issue-70935-complex-spans.stderr

One less duplicate error.

rustbot · 2026-02-09T06:14:25Z

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.

lcnr

smart, query check_coroutine_obligations only depends on query mir_built, so we don't have to do any delay_span_bug stuff here, we can just eagerly check them

View changes since this review

lcnr · 2026-02-09T14:06:35Z

@bors r+ rollup

rust-bors · 2026-02-09T14:06:39Z

📌 Commit f248395 has been approved by lcnr

It is now in the queue for this repository.

@lcnr

…es-ready, r=lcnr Check stalled coroutine obligations eagerly Fixes rust-lang#151322 Fixes rust-lang#151323 Fixes rust-lang#137916 Fixes rust-lang#138274 The problem is that stalled coroutine obligations can't be satisifed so that they cause normalization to fail in `mir_borrowck`. Thus, we failed to register any opaque to storage in the next solver. I fix it by checking these obligations earlier in `mir_borrowck`. r? @lcnr

@lcnr

…es-ready, r=lcnr Check stalled coroutine obligations eagerly Fixes rust-lang#151322 Fixes rust-lang#151323 Fixes rust-lang#137916 Fixes rust-lang#138274 The problem is that stalled coroutine obligations can't be satisifed so that they cause normalization to fail in `mir_borrowck`. Thus, we failed to register any opaque to storage in the next solver. I fix it by checking these obligations earlier in `mir_borrowck`. r? @lcnr

@lcnr

…es-ready, r=lcnr Check stalled coroutine obligations eagerly Fixes rust-lang#151322 Fixes rust-lang#151323 Fixes rust-lang#137916 Fixes rust-lang#138274 The problem is that stalled coroutine obligations can't be satisifed so that they cause normalization to fail in `mir_borrowck`. Thus, we failed to register any opaque to storage in the next solver. I fix it by checking these obligations earlier in `mir_borrowck`. r? @lcnr

@lcnr

…es-ready, r=lcnr Check stalled coroutine obligations eagerly Fixes rust-lang#151322 Fixes rust-lang#151323 Fixes rust-lang#137916 Fixes rust-lang#138274 The problem is that stalled coroutine obligations can't be satisifed so that they cause normalization to fail in `mir_borrowck`. Thus, we failed to register any opaque to storage in the next solver. I fix it by checking these obligations earlier in `mir_borrowck`. r? @lcnr

Rollup of 12 pull requests Successful merges: - #152388 (`rust-analyzer` subtree update) - #151613 (Align `ArrayWindows` trait impls with `Windows`) - #152134 (Set crt_static_allow_dylibs to true for Emscripten target) - #152166 (cleanup some more things in `proc_macro::bridge`) - #152236 (compiletest: `-Zunstable-options` for json targets) - #152287 (Fix an ICE in the vtable iteration for a trait reference in const eval when a supertrait not implemented) - #142957 (std: introduce path normalize methods at top of `std::path`) - #145504 (Add some conversion trait impls) - #152131 (Port rustc_no_implicit_bounds attribute to parser.) - #152315 (fix: rhs_span to rhs_span_new) - #152327 (Check stalled coroutine obligations eagerly) - #152377 (Rename the query system's `JobOwner` to `ActiveJobGuard`, and include `key_hash`)

@lcnr

Rollup merge of #152327 - adwinwhite:fix-non-defining-use-ices-ready, r=lcnr Check stalled coroutine obligations eagerly Fixes #151322 Fixes #151323 Fixes #137916 Fixes #138274 The problem is that stalled coroutine obligations can't be satisifed so that they cause normalization to fail in `mir_borrowck`. Thus, we failed to register any opaque to storage in the next solver. I fix it by checking these obligations earlier in `mir_borrowck`. r? @lcnr

rustbot assigned lcnr Feb 8, 2026

rustbot added 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. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Feb 8, 2026

adwinwhite commented Feb 8, 2026

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One less duplicate error.

adwinwhite commented Feb 8, 2026

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tests/ui/async-await/issue-70935-complex-spans.stderr

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One less duplicate error.

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check stalled coroutine obligations eagerly

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adwinwhite force-pushed the fix-non-defining-use-ices-ready branch from 75f0bac to 9a14380 Compare February 9, 2026 06:14

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bless tests

f248395

adwinwhite force-pushed the fix-non-defining-use-ices-ready branch from 9a14380 to f248395 Compare February 9, 2026 07:10

lcnr reviewed Feb 9, 2026

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rust-bors bot 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-review Status: Awaiting review from the assignee but also interested parties. labels Feb 9, 2026

JonathanBrouwer mentioned this pull request Feb 9, 2026

Rollup of 8 pull requests #152390

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Rollup of 12 pull requests #152391

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Rollup of 12 pull requests #152395

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Rollup of 12 pull requests #152399

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Rollup of 17 pull requests #152400

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rust-bors bot merged commit 1f0e215 into rust-lang:main Feb 9, 2026
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Check stalled coroutine obligations eagerly#152327

Check stalled coroutine obligations eagerly#152327
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