enum OpCode {
  PING,
  HELLO,
  MOVE,
}

type PingEvent = Record<string, never>;

type HelloEvent = {
  name: string;
};

type MoveEvent = {
  x: number;
  y: number;
};

type OpArgsMapping = {
  [OpCode.PING]: PingEvent;
  [OpCode.HELLO]: HelloEvent;
  [OpCode.MOVE]: MoveEvent;
};

class WebSocketClient {
  public send<TOp extends OpCode, TArgs extends OpArgsMapping[TOp]>(
    op: TOp,
    args: TArgs,
  ) {
    // ...
  }
}

function main1() {
  const client = new WebSocketClient();
  client.send(OpCode.PING, {});
}