Hojun-Cho 80e7096f25 cgen: #50 append/insert tagged-dst VALUE boxes PRE-grow, both stages ...

The #34 value-store dispatch's tagged arm ran the widen choke-point
(cg_widen_tagged_store / cgwidentaggedstore — which cgexprs the value
internally) AFTER cg_append_grow, so a value expression reading the
destination (xs.len) saw post-grow state. Hare evaluates arguments
before the call's effects; the scalar/str/slice arms already ordered
value-first. insert() inherited the bug through its desugar-to-append
(9861f73) — one boxing choke-point, so this is the whole fix. Box the
value into a fresh per-site @apptagscr frame scratch pre-grow (zero,
BP-rooted widen store), then raw-copy the finished box into the new
slot post-grow.

Consumer evidence: regex fold-5b's {,0} rows (reviewer-5b's mutant;
ken's corrected-root matrix /tmp/ken_silent, f50v4_tagged exit 15 both
stages, byte-id, gate-blind). lib/regex.ww:643-647's pre-bound
split_target workaround comment GRADUATES with this commit; the
comment update itself rides the next regex touch per the standing
rule.

test/807: 57 -> 84 fixtures. New rows: tagged_pregrow_val (f50v4
exact), scalar_pregrow_val (no-regress control), tagged_selfref_val,
tagged_str_payload, tagged_regex_minrep (the {,0} shape standalone),
tagged_append_pregrow_val (direct append, the fix site),
tagged_realloc_selfref_loop (ken k50a: old-base read across actual
rt_ensure base moves), tagged_seq_positions (ken k50b: sequenced
inserts at 0/mid, each len-reading) and tagged_void_variant (ken k50c:
tag-only box through the fresh scratch). Mutation at e8977a4 fails
exactly the five eval-order-discriminating tagged rows, both stages.

The STRUCT-LITERAL value arm keeps its post-grow field-expr fill —
same eval-order class, different arm; filed (ww-core #59), cited
at-site, not folded.

2026-06-05 09:31:23 +09:00

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