Remove `cycle_fatal` query modifier by Zoxc · Pull Request #153276 · rust-lang/rust

Zoxc · 2026-03-02T08:28:08Z

This removes the cycle_fatal query modifier as it has no effect on its current users.

The default CycleErrorHandling::Error mode does the same as cycle_fatal when the default impl of FromCycleError is used. The return types of queries using cycle_fatal however have no specialized FromCycleError impl.

nnethercote

Please expand the PR description to explain clearly why cycle_fatal has no effect. (I know, because I worked it out two days ago, but to anyone else who comes across this PR it won't be clear, and the change to the comment in plumbing.rs is easy to overlook.)

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rustbot · 2026-03-02T08:49:09Z

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

nnethercote · 2026-03-02T08:49:48Z

Blocked on #153169.

nnethercote · 2026-03-02T21:16:12Z

Blocked on #153169.

That PR has merged, and this PR is now unblocked.

rustbot · 2026-03-04T03:01:51Z

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.

nnethercote

Can you copy the PR description into the commit message? It's useful to have a good commit message, because you can see that easily when using git blame, and avoids having to work out which PR the commit belonged to. r=me with that.

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nnethercote · 2026-03-04T06:19:14Z

 // placeholder (error) value if the query resulted in a query cycle.
-// Queries marked with `cycle_fatal` do not need the latter implementation,
-// as they will raise a fatal error on query cycles instead.
+// Queries without a `Value` implementation will raise a fatal error on query


Suggested change
// Queries without a `Value` implementation will raise a fatal error on query
// Queries without a `FromCycleError` implementation will raise a fatal error on query

This removes the `cycle_fatal` query modifier as it has no effect on its current users. The default `CycleErrorHandling::Error` mode does the same as `cycle_fatal` when the default impl of `FromCycleError` is used. The return types of queries using `cycle_fatal` however have no specialized `FromCycleError` impl.

nnethercote · 2026-03-04T10:00:02Z

@bors r+ rollup

rust-bors · 2026-03-04T10:00:06Z

📌 Commit 91c7627 has been approved by nnethercote

It is now in the queue for this repository.

Remove `cycle_fatal` query modifier This removes the `cycle_fatal` query modifier as it has no effect on its current users. The default `CycleErrorHandling::Error` mode does the same as `cycle_fatal` when the default impl of `FromCycleError` is used. The return types of queries using `cycle_fatal` however have no specialized `FromCycleError` impl.

Rollup of 9 pull requests Successful merges: - #152164 (Lint unused features) - #152801 (Refactor WriteBackendMethods a bit) - #153317 (Abort after `representability` errors) - #153361 (enable `PassMode::Indirect { on_stack: true, .. }` tail call arguments) - #153402 (miri subtree update) - #153276 (Remove `cycle_fatal` query modifier) - #153396 (use `minicore` in some `run-make` tests) - #153401 (Migrationg of `LintDiagnostic` - part 7) - #153406 (Remove a ping for myself)

…uwer Rollup of 12 pull requests Successful merges: - #153402 (miri subtree update) - #152164 (Lint unused features) - #152801 (Refactor WriteBackendMethods a bit) - #153196 (Update path separators to be available in const context) - #153204 (Add `#[must_use]` attribute to `HashMap` and `HashSet` constructors) - #153317 (Abort after `representability` errors) - #153276 (Remove `cycle_fatal` query modifier) - #153300 (Tweak some of our internal `#[rustc_*]` TEST attributes) - #153396 (use `minicore` in some `run-make` tests) - #153401 (Migrationg of `LintDiagnostic` - part 7) - #153406 (Remove a ping for myself) - #153414 (Rename translation -> formatting)

Rollup merge of #153276 - Zoxc:rem-fatal-cycle, r=nnethercote Remove `cycle_fatal` query modifier This removes the `cycle_fatal` query modifier as it has no effect on its current users. The default `CycleErrorHandling::Error` mode does the same as `cycle_fatal` when the default impl of `FromCycleError` is used. The return types of queries using `cycle_fatal` however have no specialized `FromCycleError` impl.

…uwer Rollup of 12 pull requests Successful merges: - rust-lang/rust#153402 (miri subtree update) - rust-lang/rust#152164 (Lint unused features) - rust-lang/rust#152801 (Refactor WriteBackendMethods a bit) - rust-lang/rust#153196 (Update path separators to be available in const context) - rust-lang/rust#153204 (Add `#[must_use]` attribute to `HashMap` and `HashSet` constructors) - rust-lang/rust#153317 (Abort after `representability` errors) - rust-lang/rust#153276 (Remove `cycle_fatal` query modifier) - rust-lang/rust#153300 (Tweak some of our internal `#[rustc_*]` TEST attributes) - rust-lang/rust#153396 (use `minicore` in some `run-make` tests) - rust-lang/rust#153401 (Migrationg of `LintDiagnostic` - part 7) - rust-lang/rust#153406 (Remove a ping for myself) - rust-lang/rust#153414 (Rename translation -> formatting)

rustbot assigned nnethercote Mar 2, 2026

nnethercote requested changes Mar 2, 2026
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Comment threadcompiler/rustc_middle/src/query/plumbing.rs Outdated
Comment threadcompiler/rustc_middle/src/queries.rs

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 Mar 2, 2026

nnethercote added the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label Mar 2, 2026

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nnethercote removed the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label Mar 2, 2026

Zoxc force-pushed the rem-fatal-cycle branch from 6d117e7 to 8cc80efCompare March 4, 2026 03:01

nnethercote reviewed Mar 4, 2026
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Zoxc force-pushed the rem-fatal-cycle branch from 8cc80ef to 91c7627Compare March 4, 2026 07:14

nnethercote approved these changes Mar 4, 2026
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rust-borsBot 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 Mar 4, 2026

JonathanBrouwer mentioned this pull request Mar 4, 2026
Rollup of 6 pull requests #153403
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JonathanBrouwer mentioned this pull request Mar 4, 2026
Rollup of 7 pull requests #153404
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JonathanBrouwer mentioned this pull request Mar 4, 2026
Rollup of 6 pull requests #153405
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GuillaumeGomez mentioned this pull request Mar 4, 2026
Rollup of 9 pull requests #153412
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JonathanBrouwer mentioned this pull request Mar 4, 2026
Rollup of 12 pull requests #153416
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rust-borsBot merged commit fdb18d9 into rust-lang:mainMar 5, 2026
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rustbot added this to the 1.96.0 milestone Mar 5, 2026

Zoxc deleted the rem-fatal-cycle branch March 5, 2026 04:18

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Remove `cycle_fatal` query modifier - #153276

Remove `cycle_fatal` query modifier#153276
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	// Queries without a `Value` implementation will raise a fatal error on query
	// Queries without a `FromCycleError` implementation will raise a fatal error on query

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