fix: nondeterministic crash in grind congruence closure#13027
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leodemoura merged 1 commit intomasterfrom Mar 21, 2026
Merged
fix: nondeterministic crash in grind congruence closure#13027leodemoura merged 1 commit intomasterfrom
grind congruence closure#13027leodemoura merged 1 commit intomasterfrom
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`isCongruent` checked only `e₁`'s `funCC` flag when comparing two expressions, but `congrHash` uses each expression's own flag to compute its hash. When `e₁.funCC ≠ e₂.funCC`, the hash values are computed via fundamentally different paths, so declaring them congruent violates the `BEq`/`Hashable` invariant of `PHashSet`. With pointer-based hashing (`ptrAddrUnsafe`), the different hash computations can accidentally collide, leading to a nondeterministic assertion failure in `mkCongrProof`. This PR requires matching `funCC` flags in `isCongruent`, adds a regression test for funCC congruence, and fixes the debug invariant checker to skip `funCC` parents (whose parent-child relationships use one-level decomposition rather than full `getAppArgs`/`getAppFn`). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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This PR fixes a nondeterministic crash in
grindcaused by aBEq/Hashableinvariantviolation in the congruence table.
congrHashuses each expression's ownfunCCflag tocompute its hash (one-level decomposition for
funCC = true, full recursive decompositionfor
funCC = false), butisCongruentonly checked the stored expression's flag. When twoexpressions with mismatched
funCCflags accidentally hash-collided (via pointer-basedptrAddrUnsafehashing),isCongruentcould declare them congruent despite differentargument counts, leading to an assertion failure in
mkCongrProof.The fix requires matching
funCCflags inisCongruent. The PR also fixes the debuginvariant checker (
checkParents) to skipfunCCparents and adds a regression test forfunCC congruence.
Observed as a nondeterministic crash in Mathlib at
Analysis/ODE/PicardLindelof.lean.