rambda/_ts-toolbelt/src/Union/Last.ts

Lightweight faster alternative to Ramda

import {IntersectOf} from './IntersectOf'

/** Get the last item within an **union**
 * (⚠️ it might not preserve order)
 * @param U
 * @returns **any**
 * @example
 * ```ts
 * ```
 */
export type Last<U extends any> =
    IntersectOf<
        U extends unknown   // Distribute U
        ? (x: U) => void
        : never             // To intersect
    > extends (x: infer P) => void
      ? P                   // Extract merged
      : never               // ^^^ Last parameter

// The above does this (i.e.)
// ParamsOf<((a: 1) => void) & ((a: 2) => void)> // => [2]