Hojun-Cho
f3750ae3ce
io.empty (discard+EOF stream, ref/hare/io/empty.ha:4-17) — needed by getopt's two-pass printusage width measurement. Diverges from Hare's `const empty: *stream`: a `let _empty_vt` + `fn empty()` that wires the fn-ptr slots per call, because const-init of a vtable struct with fn-ptr fields is blocked (#118, ruled accept). Co-discovered while making empty() byte-identical across stages: three wwstage-only cgen fixes (cstage was already correct; wwstage aligned down): - #129 sretretsize: consult the same-module pointer-alias before structlookup's any-module struct fallback (io.stream = *vtable was mis-sized as memio's 56B struct -> spurious sret save). - #129 callsretsize: swap curmod to the callee's module before sret-size classification (cross-module callee context). - #130 cgassign global-struct tagged-union field store: add the missing arm (was a 1-word store) mirroring cstage cgen.c:4893-4912. The three are inseparable from io.empty here — splitting them out leaves a divergent-asm intermediate (993/995 red), so they ride one commit per the one-class gate-repair carve-out (#133-expanded precedent). Regenerates the embedded combined.ww; 989_lib_byteid pins bufio + fmt graduated to M_ID. (cgenexpr.ww fix-3 inline comment cites the #129 cluster; narrow to #130 on next touch to avoid a regen for a comment.)