import { Server } from "socket.io";

interface ServerToClientEvents {
  someEvent: (callback: (err: Error) => void) => void;
}
interface ClientToServerEvents {}

const io = new Server<ClientToServerEvents, ServerToClientEvents>();
io.on("connection", async (socket) => {
  // Typescript gives error "Argument of type 'string' is not assignable to parameter of type 'never'.ts(2345)"
  await socket.emitWithAck("someEvent");

  // No error
  socket.emit("someEvent", (err) => {});
});