// A `Task` allows ONE awaiter — a second concurrent `wait` on the same pending
// task would overwrite the single `waiter` slot, and completion would wake only
// the second, stranding the first forever. Regression (B1.4a review, P1-c): the
// guard aborts loudly instead of silently deadlocking.
//
// aborts (exit 134) after the diagnostic — aarch64-macOS-pinned.
#import "modules/std.sx";
sched :: #import "modules/std/sched.sx";
S :: struct { t: *sched.Task(i64); }
main :: () -> i64 {
    st : S = ---; st.t = null;
    s := sched.Scheduler.init(); ps := @s; pst := @st;
    mkprod :: (ps: *sched.Scheduler, pst: *S) { pst.t = ps.go(() -> i64 => { ps.yield_now(); 42 }); }
    mkw :: (ps: *sched.Scheduler, pst: *S) { ps.spawn(() => { x := pst.t.wait() or { -1 }; print("got {}\n", x); }); }
    mkprod(ps, pst); mkw(ps, pst); mkw(ps, pst);   // second waiter → loud abort
    s.run();
    return 0;
}