Introduce a `RerunNonErased` error type mirroring `NoSolution`, to better track when we're bailing by jdonszelmann · Pull Request #156246 · rust-lang/rust

jdonszelmann · 2026-05-06T14:29:11Z

r? @lcnr

@rustbot blocked #155443

rustbot · 2026-05-06T14:29:16Z

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

changes to the core type system

cc @lcnr

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

… type

rustbot · 2026-05-08T12:37:25Z

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.

jdonszelmann · 2026-05-08T13:50:33Z

@bors r=lcnr

rust-bors · 2026-05-08T13:50:36Z

📋 This PR cannot be approved because it currently has the following label: S-blocked.

jdonszelmann · 2026-05-08T13:51:35Z

@bors r=lcnr

rust-bors · 2026-05-08T13:51:39Z

📋 Only open, non-draft PRs can be approved.

jdonszelmann · 2026-05-08T13:52:22Z

@bors r=lcnr

rust-bors · 2026-05-08T13:52:25Z

📌 Commit 180725c has been approved by lcnr

It is now in the queue for this repository.

…uwer Rollup of 4 pull requests Successful merges: - #156246 (Introduce a `RerunNonErased` error type mirroring `NoSolution`, to better track when we're bailing) - #156038 (turn `compute_goal_fast_path` into a single match) - #156291 (Treat MSVC "performing full link" message as informational) - #156301 (Avoid ICE when suggesting as_ref for ill-typed closure receivers)

@lcnr

Rollup merge of #156246 - jdonszelmann:rerun-error-type, r=lcnr Introduce a `RerunNonErased` error type mirroring `NoSolution`, to better track when we're bailing r? @lcnr @rustbot blocked #155443

lcnr · 2026-05-11T10:56:26Z

+                Ok(i) => Ok(i),
+                Err(NoSolutionOrRerunNonErased::NoSolution(NoSolution)) => Err(NoSolution),
+                Err(NoSolutionOrRerunNonErased::RerunNonErased(_)) => {
+                    // check th t the opaque_accesses state mirrors the result we got.


Suggested change

// check th t the opaque_accesses state mirrors the result we got.

// check that the opaque_accesses state mirrors the result we got.

View changes since the review

lcnr · 2026-05-11T10:57:28Z

        if self.typing_mode().is_erased_not_coherence() {
-            self.opaque_accesses.rerun_always(RerunReason::EvaluateConst);
-            return None;
+            self.opaque_accesses.rerun_always(RerunReason::EvaluateConst)?;


Suggested change

self.opaque_accesses.rerun_always(RerunReason::EvaluateConst)?;

match self.opaque_accesses.rerun_always(RerunReason::EvaluateConst)? {}

View changes since the review

lcnr · 2026-05-11T10:57:39Z

        if self.typing_mode().is_erased_not_coherence() {
-            self.opaque_accesses.rerun_always(RerunReason::MayUseUnstableFeature);
-            return false;
+            self.opaque_accesses.rerun_always(RerunReason::MayUseUnstableFeature)?;


Suggested change

self.opaque_accesses.rerun_always(RerunReason::MayUseUnstableFeature)?;

match self.opaque_accesses.rerun_always(RerunReason::MayUseUnstableFeature) {}

View changes since the review

lcnr · 2026-05-11T10:58:25Z

+
+        outer.opaque_accesses.update(nested.opaque_accesses)?;
+
+        let r = match r.map_err_to_rerun()? {


what is this match doing 🤔 and this ? could be an unwrap, can it?

View changes since the review

lcnr · 2026-05-11T11:00:16Z

                            ecx.add_goal(GoalSource::Misc, goal.with(cx, PredicateKind::Ambiguous));
                            return ecx
-                                .evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
+                                .evaluate_added_goals_and_make_canonical_response(Certainty::Yes)


this is surprising, how does evaluate_added_goals_and_make_canonical_response not return NoSolutionOrRerunErased

View changes since the review

lcnr · 2026-05-11T11:00:39Z

+                let alias_bound_result = match alias_bound_result.map_err_to_rerun()? {
+                    Ok(i) => Ok(i),
+                    Err(NoSolution) => Err(NoSolution),
+                };


why this match?

View changes since the review

lcnr · 2026-05-11T11:01:42Z

+                let result = match result {
+                    Ok(i) => Ok(i),
+                    Err(NoSolutionOrRerunNonErased::NoSolution(NoSolution)) => Err(NoSolution),
+                    Err(NoSolutionOrRerunNonErased::RerunNonErased(e)) => {
+                        return Err(e.into());
+                    }
+                };


why not the map_err_rerun thingy? here

View changes since the review

lcnr · 2026-05-11T11:02:07Z

            );

-            then(ecx, maximal_certainty)
+            then(ecx, maximal_certainty).map_err(Into::into)


this map_err(Into::into) is a noop afaict?

same for a lot of them

View changes since the review

lcnr · 2026-05-11T11:03:12Z


        let result = ecx.probe(|_| ProbeKind::UnsizeAssembly).enter(
-            |ecx| -> Result<Vec<Candidate<I>>, NoSolution> {
+            |ecx| -> Result<Vec<Candidate<I>>, NoSolutionOrRerunNonErased> {


this feels still suboptimal, should be Result<Vec<Candidate<I>>, RerunNonErased>

View changes since the review

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 May 6, 2026

rustbot assigned lcnr May 6, 2026

rustbot added the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label May 6, 2026

lcnr reviewed May 6, 2026

View reviewed changes

Comment thread compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs Outdated

lcnr reviewed May 6, 2026

View reviewed changes

Comment thread compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs

lcnr reviewed May 6, 2026

View reviewed changes

Comment thread compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs Outdated

jdonszelmann force-pushed the rerun-error-type branch from 13753cc to 56bbe1c Compare May 7, 2026 06:02

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jdonszelmann added 2 commits May 8, 2026 14:10

return faster from internal iterators

687f839

consistently encode failure reason (nosolution or rerun) in the error…

180725c

… type

jdonszelmann force-pushed the rerun-error-type branch from aaf1151 to 180725c Compare May 8, 2026 12:37

jdonszelmann removed the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label May 8, 2026

jdonszelmann closed this May 8, 2026

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 8, 2026

jdonszelmann reopened this May 8, 2026

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 8, 2026

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 May 8, 2026

JonathanBrouwer mentioned this pull request May 8, 2026

Rollup of 4 pull requests #156324

Merged

rust-bors Bot merged commit fd16638 into rust-lang:main May 8, 2026
22 checks passed

rustbot added this to the 1.97.0 milestone May 8, 2026

lcnr reviewed May 11, 2026

View reviewed changes

	// check th t the opaque_accesses state mirrors the result we got.
	// check that the opaque_accesses state mirrors the result we got.

	self.opaque_accesses.rerun_always(RerunReason::EvaluateConst)?;
	match self.opaque_accesses.rerun_always(RerunReason::EvaluateConst)? {}


		outer.opaque_accesses.update(nested.opaque_accesses)?;

		let r = match r.map_err_to_rerun()? {

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