You might as well avoid wrapping the types and just split the writer and reader: it's good practice to do this anyway, since you probably only need one half of

You might as well avoid wrapping the types and just split the writer and reader: it's good practice to do this anyway, since you probably only need one half of the oneshot channel on each side and having a handle to something that can both read and write seems like a logic error. You can also augment the writer function to throw into the promise, if required! type Sender<T, E = unknown> = ((e: null, v: T) => void) & ((e: E) => void); function oneshot<T, E = unknown>(): [Promise<T>, Sender<T, E>] { let send: Sender<T, E>; const recv = new Promise<T>((resolve, reject) => { send = (err, v?: T) => err == null ? resolve(v!) : reject(err); }); return [recv, send!]; }