Re-home the proven first-wins race from sched.race(*Task) onto *Future handles
+ the Io protocol; the old Task-based race is REPLACED (ufcs overload-by-receiver
is rejected, and only 1821 used it).
- Protocol: add Io.current_park() -> ParkToken — the running fiber as a token,
captured WITHOUT parking — so race can register the SAME coordinator across N
futures' park slots, then park once via suspend_raw; any completion readies it.
Scheduler returns {self.current} (bails outside a fiber); CBlockingIo returns
{null} (race never parks there — futures are born .ready).
- race :: ufcs (io: Io, futures: $T) -> RaceResult(T), kept in sched.sx (it needs
meta.sx's make_enum/make_variant; pulling that into the io.sx prelude part-file
would cycle). Winner scan -> register/park/deregister -> make_variant the winner
-> Phase-3 cancel each still-.pending loser (no join). RaceResult reused
unchanged (*Future(R) projects field 0 'value' -> R).
- TRUE-cancel: parked losers stop at their next suspend (timers evicted by cancel's
wake), so race returns at WINNER-time, not slowest-loser-time.
- Adversarial review fixes: (1) an all-failing/all-cancelling racer set no longer
deadlock-aborts the scheduler — race bails loudly ('all futures settled without
a winner') when nothing is .ready and nothing is still .pending; (2) only
.pending losers are cancelled, so a loser that already .failed keeps its real
outcome label instead of being stomped to .canceled.
Re-point 1821 to context.io.async + context.io.race (winner a=111, losers
.canceled, completion log only 'task 1 @ 10ms', final clock 10ms — was 30 under
the old cooperative join). New 1826 locks the failing-loser case. Byte-identical
on aarch64-macOS + aarch64-linux. Suite 853/0; .ir churn is the current_park
vtable method.
A cancelled async worker now abandons its body at its next suspend instead
of running to completion.
- Cancel-flag back-ref (D4): SpawnOpts.cancel_flag (core.sx) + Fiber.cancel_flag
(sched.sx), set from opts.cancel_flag in Scheduler.spawn_raw; async passes
xx @f.canceled (the Future.canceled Atomic(bool) erased to *void).
- Delivery: Scheduler.suspend_raw consults fiber_canceled(self.current) PRE-park
(raise without parking — no deadlock if cancel landed before the worker ran)
and POST-resume (cancel landed while parked), raising error.Canceled.
cancel(f) flips the sticky flag, marks .canceled, and wakes the worker.
- async worker is failable Closure() -> ($R, !); the completion closure
f.value = worker() catch {…} marks .canceled/.failed and wakes the awaiter,
so post-suspend side effects never run. New failable io.sleep(ms) is the
cancellation point.
- Compiler: a -> ! fn whose only error source is try-ing a protocol method
(io.suspend_raw) was wrongly flagged 'declared ! but never errors';
collectErrorSites now marks a try of a non-identifier callee as a dynamic
(opaque) error source, suppressing the warning.
- Two UAFs found by adversarial review and fixed: (1) cancel-before-park
orphaned io.sleep's armed timer — suspend_raw's pre-park raise now evicts the
current fiber's timer/waiter first; (2) cancel(f) could wake a reaped worker —
now only wakes when was_pending.
Migrated 1805/1806/1824 to failable workers. Lock: example 1825 (seq: 1 -99,
post-suspend line never runs); byte-identical on aarch64-macOS + aarch64-linux.
.ir churn is the SpawnOpts layout change (type-table string renumbering).
