[ty] Temporary fix for PropagatedPanic crashes#25463
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PropagatedPanic crashes
MichaReiser
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May 29, 2026
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| #[cfg(test)] | ||
| pub(crate) mod cancellation_tests { |
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TODO, remove. I only needed these to verify the issue
MichaReiser
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May 29, 2026
| /// WARNING: Triggers a new revision, canceling other database handles. This can lead to deadlock. | ||
| pub fn system_mut(&mut self) -> &mut dyn System { | ||
| self.trigger_cancellation(); | ||
| self.synthetic_write(Durability::LOW); |
Typing conformance resultsNo changes detected ✅Current numbersThe percentage of diagnostics emitted that were expected errors held steady at 91.94%. The percentage of expected errors that received a diagnostic held steady at 87.09%. The number of fully passing files held steady at 92/134. |
Memory usage reportMemory usage unchanged ✅ |
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This made me realise that the most simplistic fix in salsa isn't much harder than always bumping the revision when a fixpoint query was cancelled. Closing, given that it shouldn't take me much time to land this fix upstream (see salsa-rs/salsa#1100), |
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Summary
This is a workaround for #3339 to give me some more time to implement a proper fix in Salsa.
The issue is that the fixpoint computation incorrectly assumes that the only reason a fixpoint query can panic is a bug in the implementation. In which case it doesn't make sense to re-run the query within the same revision because it is only going to panic again (we don't re-run the query in the same revision because there are stale values from the previous revision that Salsa might end up picking up as fresh values). However, that's not the case. The query can also panic if the execution gets cancelled because another thread tries to write (tries to acquire a mut db).
This PR works around this limitation by changing all code paths in ty where we acquire a &mut Db without bumping the revision so that we bump the revision instead. This has the downside that Salsa has to do a little more work to verify that it's okay to reuse all cached queries (because nothing changed). But this seems clearly better than just crashing (and many users seem to be running into this).