[Hooks] What is accepted on useEffect's 2nd argument

I assume currently it only do equal (===) comparison, since passing array of array isn't preventing it.

import React, { useState, useEffect } from 'react';

export default () => {
  let [count, setCount] = useState(0);
  let guard = [0, 1, 2];
  useEffect(() => {
    setTimeout(() => {
      setCount(count + 1);
    }, 2000); // delay to prevent lagging
  }, [guard]);
  return <div>{count}</div>;
};

I don't find anything in current documentation. I think it is needed to add accepted types passed into that 2nd argument.

On side note, I wonder what In the future, the second argument might get added automatically by a build-time transformation. phrase means.

Comienza con el punto de entrada de la documentación de useEffect y el ejemplo de nested-array del issue; verifica qué acepta el segundo argumento y cómo se describe la comparación de dependencias. Explica también la frase citada sobre build-time-transformation. Se considera terminado cuando la documentación responde claramente a ambas preguntas, incluido el comportamiento del ejemplo.