improvise-ir7l. project::cell_id decided Record vs Aggregate purely on whether
a regular category sat on Axis::None; it never asked whether the coordinate
named a formula target. So a formula cell was a Record, render.rs::editable
said true, and a write to it landed, was stored, and was then shadowed forever
by formula_cache — not a revert, a permanent silent shadow, on the demo's
front page.
Rather than a second "but not really" flag beside CellId (the two-answers
shape ADR 002 exists to forbid), a formula-owned cell now projects a different
kind of identity. Derived carries the formula's target and no surrogate, so
the write is unconstructible rather than refused.
The predicate is Model::formula_for(&CellKey), one home, which already existed
three times open-coded inside model/types.rs. The TUI lands in the same change:
EditOrDrill calls the same predicate and refuses, or the two front ends
diverge.
Two orderings are load-bearing and tested: Derived is asked before the record
branch (the coordinate is stored), and after the aggregate branch (gotcha 10 —
an aggregating formula cell is still drillable).
Two tests were passing while their names were false for the Profit column and
are renamed and two-sided now.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Edward Langley
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