The cg_widen_tagged_store / cgwidentaggedstorebp struct-payload arm
gated the 3-word {ptr,len,cap} field store on TY_STR only; a slice-
typed field inside a union-payload struct literal fell to the scalar
tail and silently dropped .len/.cap (the #24 gap's widener twin, both
stages symmetric so byte-id gates were blind). Surfaced by #38's
regex-shaped consumer: wide{xs: []u8, ys: []u8, n} widened into
(wide | error | nomem).
Hojun-Cho
5f15eb3d09