pushargsrev's five aistagged gates (N_IDENT #55, N_CALL #21, N_INDEX
#12, N_DOT #22a, deref #35) treated a tagged arg as already-tagged
when its SLOT SIZE matched the param's. A same-slot subset union
((bool|void) into (i64|bool|void), both 16B) then natural-pushed the
narrower box's words carrying SOURCE tags — no re-layout, no
cg_widen_tag_remap twin — so the callee matched the wrong arm
(silent: probes exited 10/90 where cstage exits 30/27). cstage keys
widen detection on type equality (cgen.c:10000 same = (pu == au) ||
type_eq) and routes every non-same tagged source through the zeroed
scratch + tag remap; the slot-DIFFER wwstage path already mirrored
that byte-identically, so the fix computes cstage's same check once
(wsame) and replaces each slot-size test with it. This also erases
the last known cs!=ww shape divergence (the 16B-local staging vs
direct-push frame delta on prefix subsets).
8 subsetwiden_* fixtures own the class: call-result/ident/str-payload
/mid-arg remap (the wrong-arm shapes), prefix (the shape-divergence
repro), and bigslot/return-pos/struct-24-to-32 sibling guards. Corpus
pin 1740/343/22/209/1166/3480.
Hojun-Cho
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