UnionTo.ts

// both examples below start
type UnionToXXX<T> = (T extends any ? (t: T) => T : never) extends infer U ?  // rest 

// Converts { x: string } | { y: number } to { x: string, y: number }
type UnionToIntersection<T, U = T> = (U extends any ? (arg: U) => any : never) extends ((arg: infer I) => void) ? I : never;

// Converts string | number | boolean to [string, number, boolean]
type UnionToTuple<T> = (
(
  (
    T extends any
      ? (t: T) => T
      : never
  ) extends infer U
    ? (U extends any
      ? (u: U) => any
      : never
    ) extends (v: infer V) => any
      ? V
      : never
    : never
) extends (_: any) => infer W
  ? [...UnionToTuple<Exclude<T, W>>, W]
  : []
);