Flow type-level lists

type-list.js

// @flow

// Type-level lists
type Empty = []

// Type-level tail function
type Tail<L> = $Call<FTail, L>
interface FTail {
  (Empty): Empty,
  <H, T>([H, T]): T
}

// Use plain tuples for cons
type L1 = [string, Empty]
type L2 = [number, L1]
type L3 = [boolean, L2]

// Call tail
type L4 = Tail<L3>
type L5 = Tail<L4>

// Ok, let's provide some values to prove it works
let l2: L2 = [1, ['a', []]]

let l2Also: L4 = l2

let l5: L5 = ['b', []]
let l2Again: [number, L5] = [1, l5]