Control flow analysis for dependent parameters only works when checking against literals #55766

const fnLiteral: (...args: [`a`, number] | [`b`, string]) => void = (a, b) => {
  if (a === "a") {
    console.log(b);
    //          ^? number
  }
}

const fnAssert: (...args: [`a`, number] | [`b`, string]) => void = (a, b) => {
  if (isA(a)) {
    console.log(b);
    //          ^? number | string
  }
}
const fnTypeof: (...args: [number, number] | [string, string]) => void = (a, b) => {
  if (typeof a === "number") {
    console.log(b);
    //          ^? number | string
  }
}

function isA(val: unknown): val is `a` {
  return true;
}