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.)
Ports ref/hare/io handle.ha: a handle is (file | *stream); ww stream is already *vtable (#94 collapse) so the payload is (file | stream). file=i32 (Hare int is 32-bit, ww int is 8B word -- width-faithful, USER-ruled). read/write/close/seek/tell match on the handle: file-arm to os.read/write/close/lseek (os plays Hare sys role), stream-arm to the unchanged st_* vtable bodies; seeker is the 4th vtable slot (copier deferred). On a file-arm syscall error the stub returns errors.unsupported with a #199b marker -- faithful errno to io.error needs io.error to spread ...errors.error (#204/#199b-blocked); only the error value is lossy until then, the type stays faithful. Regenerates w6c/wwdump combined.ww.
The Option-C parallel _v vstream API was scaffolding to bring the io stack up alongside the old surface; carrying both permanently is a rule-9 divergence from ref/hare, which has exactly one io surface. Collapse onto that surface (stream = *vtable, ref/hare/io/stream.ha) and rename the _v symbols to their Hare names (io vstream->stream, fmt vfprint->fprint, bufio/memio/log surfaces, log.new). Deletes the 4 lib/*/vstream.ww scaffold files; regenerates w6c/wwdump combined.ww. cstage and wwstage stay byte-identical and combined_ww_fresh holds; all 220 tests pass.
Additive: keeps lib/io/io.ww's pre-vtable `stream` struct +
`read`/`write`/`close` wrappers (fold-e2-eN migrates the legacy
surface to vtable-backed implementations and retires it).
lib/io/stream.ww — vtable struct (reader/writer/closer slots,
spelled `(*T | void)` per #192 — ww parser rejects `nullable *T`),
vstream = *vtable, and the st_read/st_write/st_close dispatchers
per ref/hare/io/stream.ha:33-68. Void-arm `return e;` chains two
direct widens: concrete `errors.unsupported` → `error` (#199 α)
then `error` → (size|eof|error) (#205 NAMED-variant nominal at
tagged→tagged subset). Hare's `?`-propagating st_close collapses
to a direct `return (*c)(s);` because #173 is still open; the
surface stays Hare-shaped.
lib/io/types.ww — retarget reader/writer/closer fn-aliases from
*stream to vstream. Extend `error` union to include
`errors.unsupported` explicitly (no spread — per ken's #204-block
the wrapper-vs-flatten layout asymmetry would mis-widen; the
deferred fix is filed as #199b layout-extension).
test/wcc/775_io_vtable_run.c — 7-row sentinel: reader/writer/
closer × {set, void} happy paths + branched-callee runtime.
Rows verify the call runs + the constant exit; the void-arm
rows do NOT inspect the resulting variant tag (deferred #199b
wrapped-slot tag-remap mis-routes to dst tag 0). Cstage and
wwstage emit byte-identical asm on every row.
test/wcc/768_io_types_run.c — track the alias retarget; rows
now build a vtable, pass `&vt` (= vstream), and call through
the fn-VALUE param shape.
Combined.ww regen for w6c + wwdump per #110: lib/errors lands
transitively via the new `import errors;` in types.ww.
Sibling filed inline (NOT fixed): the checker rejects bare
`&fn_name` / `let p: *alias = &fn` assignment to a
`(*alias | void)` field — the structural `*fn(...)` value isn't
accepted as the `*alias` NAMED variant. Both stages reject.
Probes route around via explicit `(&fn): *io.reader` cast at
each vtable-field assignment.
read → (i32 | eof | closed), write → (i32 | closed),
close → (void | closed). `type eof = void` and `type closed = void`
are exported as named-void variants — distinct nominal tags despite
identical (zero-byte) payloads.
No existing callers exercised the eof/closed sentinels (the smoke
test mimics the stream pattern with its own local types), so the
graduation is purely API shape — no callsite churn.
