The scalar contract said "identity" and enforced only "scalar", so two
ways to hold an id that is not one survived.
NaN passes `type(x) == "number"` and then errors at
`p.collapsed[row.id]` with "table index is NaN" — the one scalar Lua
accepts as a number and refuses as a key. Bitten with the check
removed, it reports exactly that, from inside listview, naming no row.
DUPLICATES do not merely collide. Every lookup here — `line_of_id`, and
toggle's scan for the row index — resolves an id to the FIRST row
bearing it, so selecting the second such row toggles the first and
re-seats the cursor onto it: a stray jump with nothing pointing at the
id. Bitten with the check removed, nothing is raised at all.
Both are enforced in `check_ids`, where rows already enter, so the
error names the offending row (and, for a duplicate, both of them)
instead of surfacing as a low-level error or a wrong jump later. The
error text says why, not just what, since the reason is not guessable
from the rule.
Verified: fmt, clippy, diff-check, --lib 1897/0, crdt 2082/0, listview
26/26, m4 150/0, gpu 221/0, bottom_panel_stage1 47/47.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Levi Neuwirth
ef99b64f95