Motivation
----------
The C7 realization note (cd3d1ca / 049f22a) deferred this step: with
Scalar split into { kind, cell }, the tag-free Cell could become the
hot-path carrier, but eval and the edges still flowed the fatter
self-describing Scalar. This lands the swap.
Change
------
- Node::eval now returns Option<&[Cell]>; every node out-buffer is
[Cell; N]. The inter-node forward copies the row into a Vec<Cell> and
pushes each field via a new branch-free, infallible AnyColumn::push_cell
— the edge from_field->slot kind match is verified once at bootstrap
(C7), so the runtime push needs no per-value kind check. It only removes
a Result the forward path already .expect()ed.
- Scalar stays on the self-describing dynamic boundaries: the param plane
(build / bind / compile_with_params / sweep points / RunManifest),
AnyColumn::get (the type-erased read for sinks / serde), and source
ingestion (Source::next, the heterogeneous C3 merge). The fallible
AnyColumn::push is retained for ingestion + the kind-guard tests.
Trade
-----
The per-value runtime kind check on node OUTPUT is removed: a node that
builds a wrong-kind cell pushes raw bits with no panic. This is the same
authoring-bug class C8 already leaves to a debug_assert (output width);
node-output-kind correctness is the node's declared FieldSpec contract,
caught by each node's own eval test. Cross-node kind agreement still rests
on the bootstrap kind-check (bootstrap_rejects_*_kind_mismatch, green).
Tests
-----
Behaviour-preserving (C1): 285 green, 0 red. The only test-expectation
edits are carrier re-spellings (Scalar::f64(x) -> Cell::from_f64(x)) of
identical values; test column writes and out-of-graph channel rows stay
Scalar (the spec's three-role rule). Adds an AnyColumn::push_cell
round-trip test plus a cross-kind end-to-end forward test (a mixed
f64/i64 record whose bit patterns diverge across kinds — pins the i64
forward path the f64-only tests cannot catch). Ledger C7/C8 notes updated.
Gates: cargo build / test / clippy --all-targets -D warnings / doc
--workspace all clean.
closes#74
Brummel
82635fa259