TypeScript Control Flow Analysis indirections support

retool-typescript-control-flow-analysis-4.ts

function doSomething(x: string | number | boolean) {
  const isString = typeof x === "string"
  const isNumber = typeof x === "number"
  const isStringOrNumber = isString || isNumber

  if (isStringOrNumber) {
    x
    // `x` is of type `string | number`

    if (typeof x === "number" && x > 0) {
      x
      // `x` is of type `number`
    }
  } else {
    x
    // `x` is of type `boolean`
  }
}