Hojun-Cho
33f940e17c
Compound `OP=` through an index (gs[i]/a[i]) or a bare ident (g) on a tagged union silently misbehaved: cstage dropped the index compound and plain-stored, and BOTH stages compiled an ident compound into an add on the tag word -- byte-identical, so the gate stayed green while the tag was corrupted. A compound op on a whole union is nonsense. Gate the index plain-store arm on TK_ASSIGN so a compound falls to the existing #133 reject (wwstage's byte-id twin); add a dedicated #21 ident reject in both stages. This closes the compound half of the tagged-payload write class (deref #18, dot #34 already reject). #19 (global tagged-array static-init DATA) is a separate emitter, still open.