HermitCrab: track exact analysis feature inversion and chained override parse loss #504
Description
Valid words can lose their analyses when one affix overwrites features set by another. This issue tracks exact feature inversion: recovering valid derivations without admitting invalid ones.
Who is affected: HermitCrab users with chained feature-changing rules, and PanGloss maintainers using Machine as their correctness baseline.
The existing chained-output-feature-override-loss fixture reproduces the loss at conformance revision 8bad1934. Current master and PR #494 still need separate reruns. PanGloss has an Exact implementation; that alone does not establish general correctness.
Done when: the chosen fix has failing-before/passing-after evidence, preserves complete parse identities and multiplicities, rejects invalid neighbors, and covers nested features, absent paths, variables, and disjunctions. Reconcile it with #493's template-feature change and #505's merge investigation. Treat skips and timeouts as incomplete evidence.
Reproduction, evidence, and remaining checks
Reuse edge-cases/chained-output-feature-override-loss in the conformance suite; do not duplicate it.
For zudiua: ZUD + INNER writes tense=pres; OUTER overwrites it with past; OUTERMOST requires past. Forward synthesis justifies the parse. Negative control zudia lacks the overwrite.
The six-word check completed every row at 8bad193454a14422a3be59c3156513691ae3da3b: four positive controls and the rejection passed; valid zudiua still returned no parse.
Earlier Exact evidence and the post-#493 rerun request remain relevant. Historical Add/PriorityUnion losses are not substitutes for pinned current-head runs.
Activity
johnml1135 commentedon Sep 15, 2026
Fresh focused check: the existing six-word override-loss grammar was evaluated with the C# harness built at conformance head 8bad193. All words completed. zud, zudi, zudu and zudua returned their expected identities; zudia returned no parse as expected; valid zudiua still returned no parse. This confirms the fixture remains discriminating at that conformance revision, not that current master or current PR #494 has been rerun.
Four fixtures' notes now say what their words pin: exclude semantics …