Construct Tuple

In this medium-level challenge, you'll implement ConstructTuple<L> which builds a tuple of unknown elements with exactly the specified length.

[object Object]

type cases = [
  Expect<Equal<ConstructTuple<0>, []>>,
  Expect<Equal<ConstructTuple<2>, [unknown, unknown]>>,
  Expect<Equal<ConstructTuple<999>['length'], 999>>,
  // @ts-expect-error
  Expect<Equal<ConstructTuple<1000>['length'], 1000>>,
]

Detailed Explanation

type ConstructTuple<L extends number, R extends unknown[] = []> =
  R['length'] extends L
    ? R
    : ConstructTuple<L, [...R, unknown]>

How it works:

• We use an accumulator tuple R that starts as an empty array []
• R['length'] extends L checks if the accumulator has reached the desired length
• If the length matches, we return the accumulated tuple R
• Otherwise, we recurse by appending one unknown element with [...R, unknown]
• This builds the tuple one element at a time until it reaches length L
• Note that TypeScript has a recursion depth limit, so ConstructTuple<1000> will trigger a ts-expect-error as expected in the test cases

This challenge helps you understand recursive tuple construction and accumulator patterns in TypeScript's type system and how to apply this concept in real-world scenarios.