Future

pub fn Future(Result: type) type {
    return struct {
        any_future: ?*AnyFuture,
        result: Result,

        /// Equivalent to `await` but places a cancelation request. This causes the task to receive
        /// `error.Canceled` from its next "cancelation point" (if any). A cancelation point is a
        /// call to a function in `Io` which can return `error.Canceled`.
        ///
        /// After cancelation of a task is requested, only the next cancelation point in that task
        /// will return `error.Canceled`: future points will not re-signal the cancelation. As such,
        /// it is usually a bug to ignore `error.Canceled`. However, to defer handling cancelation
        /// requests, see also `recancel` and `CancelProtection`.
        ///
        /// Idempotent. Not threadsafe.
        pub fn cancel(f: *@This(), io: Io) Result {
            const any_future = f.any_future orelse return f.result;
            io.vtable.cancel(io.userdata, any_future, @ptrCast(&f.result), .of(Result));
            f.any_future = null;
            return f.result;
        }

        /// Idempotent. Not threadsafe.
        pub fn await(f: *@This(), io: Io) Result {
            const any_future = f.any_future orelse return f.result;
            io.vtable.await(io.userdata, any_future, @ptrCast(&f.result), .of(Result));
            f.any_future = null;
            return f.result;
        }
    };
}