Pattern matching in typescript example

.ts

type LinkedList<A> = {} | { head: A; tail: LinkedList<A> };

type ToUnion<T> = T extends { head: infer N; tail: infer Tail }
  ? N | ToUnion<Tail>
  : never;

type ToArray<T> = T extends { head: infer N; tail: infer Tail }
  ? [N, ...ToArray<Tail>]
  : [];

type myList = { head: 1; tail: { head: 4; tail: { head: 2; tail: {} } } };

type foo = ToUnion<myList>; // 1 | 4 | 2
type bar = ToArray<myList>; // [1, 4, 2]