This PR fixes a `grind` congruence-table invariant violation that could
panic
when an `ite` branch was internalized lazily (after the condition became
`True`
or `False`) and that branch's equivalence class was later merged with
another.
`Internalize.lean` has a special case for `ite` that internalizes only
the
condition; the `then`/`else` branches are skipped and only internalized
later
on demand by `propagateIte`. The on-demand path (`applyCongrFun`) called
`internalize` for the branch but never called `registerParent` to add
the
parent `ite` to the branch's parent set in the e-graph. Subsequent
merges of
the branch's equivalence class then skipped re-hashing the `ite` in the
congruence table, leaving an orphan entry whose `congr` chain no longer
matched
the table's representative.
The fix adds the explicit `registerParent e rhs` that the standard
`for arg in args` loop in `Internalize.lean` would have made for an
ordinary
application argument; we are simply mirroring that pattern lazily. The
same
helper is reused by `propagateDIte`, but with parent registration
disabled
(controlled by a new `ite : Bool` parameter): for `dite` the `rhs`
propagated
upwards is a *constructed* reduction (built via `mkApp` from `e`'s
children,
possibly post-`preprocess`), not a structural argument of `e`, so
registering
`e` as its parent would be incorrect. The lambda branches of a `dite`
are
already eagerly internalized as parents of `e` by `Internalize.lean`, so
this
case does not need the fix.
---------
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
316c39ffe4