Hojun-Cho
cbf10427df
pushargsrev's widening detection was N_IDENT-only — N_INDEX of a sum-typed slice element fell through to the scalar widening branch, which hardcoded the param's first-variant tag (MOVQ $1, AX) and pushed AX as a single scalar word. Callees that match-dispatched on the runtime tag always ran the static-guess arm on garbage. cstage knew the arg's type via check.c so its widen[] flag stayed off and the natural-push tagged-arg arm pushed CX/DX/AX (high → low) high → low. wwstage now mirrors via two narrow arms in pushargsrev: the aistagged guard treats N_INDEX-of-sum-typed-element matching the param slot as already-tagged, and the natural-push fallthrough emits PUSHQ CX / DX / AX for the same shape. Both arms gate on istaggedtype(indexvaluetnode(arg)) so literal- and ident-source sum args stay on their existing paths. Sentinel 749_sumtype_forward table-drives the three forward shapes (N_INDEX, N_IDENT, literal) and asserts per-stage runtime plus a byte-id window over the callsite asm. Combined.ww regen for wwdump_ww and w6c_ww follows the cgen source change; smoke.combined.ww unaffected. Tests: 123/123 pass; bootstrap fixed point holds (ww2==ww3==ww4).