type LengthMinusOne<T extends any[]> = T extends []
  ? -1
  : T extends [infer _, ...infer Rest]
    ? Rest['length']
    : never;

type Last<T extends any[]> = T[LengthMinusOne<T>];

import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Equal<Last<[3, 2, 1]>, 1>>,
  Expect<Equal<Last<[() => 123, { a: string }]>, { a: string }>>,
]