Show the nested goal chain for the next solver overflow FCW - #161341
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adwinwhite wants to merge 5 commits into
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Show the nested goal chain for the next solver overflow FCW#161341adwinwhite wants to merge 5 commits into
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| @@ -344,6 +344,10 @@ pub struct InferCtxt<'tcx> { | |||
| /// checking so we disable the FCW there as well. | |||
| enable_next_solver_overflow_fcw: bool, | |||
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change this to a Cell instead? 🤔
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| { | ||
| self.in_next_solver_overflow_fcw.set(true); | ||
| let ret = f(); | ||
| self.in_next_solver_overflow_fcw.set(false); |
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feels safer to replace previous entry and then revert to that one in functions like this, otherwise nesting it twice breaks the outer call
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adwinwhite
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August 20, 2026 08:35
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Some changes occurred to the core trait solver cc @rust-lang/initiative-trait-system-refactor |
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☔ The latest upstream changes (presumably #161043) made this pull request unmergeable. Please resolve the merge conflicts by rebasing. |
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| /// We need to disable the fcw if we're already in a fcw emitting to avoid | ||
| /// indefinite triggering. | ||
| pub fn enter_next_solver_overflow_fcw<F, R>(&self, mut f: F) -> R |
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Suggested change
| pub fn enter_next_solver_overflow_fcw<F, R>(&self, mut f: F) -> R | |
| pub fn with_disabled_next_solver_overflow_fcw<F, R>(&self, mut f: F) -> R |
maybe? the current name feels a bit unclear to me
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Aug 21, 2026
| nested_goals: &evaluation_result.nested_goals, | ||
| min_reachable_available_depth: AvailableDepth( | ||
| available_depth.0 - evaluation_result.required_depth, | ||
| available_depth.0 - evaluation_result.required_depth.0, |
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impl Sub<RequiredDepth> for AvailableDepth and use it in these 2 places
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| = help: consider increasing the recursion limit by adding a `#![recursion_limit = "16"]` attribute to your crate (`fcw_on_normalization`) | ||
| = help: or consider adding a manual `impl` of auto traits like `Send` for intermediate types, if auto traits are involved | ||
| = note: which requires <W<W<W<W<W<W<W<W<W<()>>>>>>>>> as HasAssoc>::Assoc == () | ||
| = note: which requires <W<W<W<W<W<W<W<W<()>>>>>>>> as HasAssoc>::Assoc == () |
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why does this stop after 2 goals? that's surprising
lcnr
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Aug 21, 2026
| } | ||
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| fn visit_goal(&mut self, goal: &inspect::InspectGoal<'_, 'tcx>) -> Self::Result { | ||
| self.predicates.push(goal.goal().predicate); |
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does this currently print both NormalizesTo and the Projection goal? if so, we should probably filter the NormalizesTo goal here :>
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Previously we only showed a single root goal for the FCW. It was difficult to find out how the goal overflowed.
We display a proving chain now which should help users identify relevant types or auto traits.
This will affect perf for crates emitting the FCW. E.g.
calimero-storegoes from 4.7s -> 5.7s in local testing since it emits thousands of FCWs internally. The FCW is a mitigation of future hard error and authors are expected to resolve it so it's probably acceptable. It doesn't affect crates without the FCW.r? lcnr