Shift

In this medium-level challenge, you'll implement the type-level version of Array.shift, which removes the first element from a tuple type and returns the remaining elements.

type Result = Shift<[3, 2, 1]> // [2, 1]

Detailed Explanation

type Shift<T extends unknown[]> = T extends [infer _First, ...infer Rest]
  ? Rest
  : []

How it works:

• The generic constraint T extends unknown[] ensures that Shift only accepts array/tuple types, causing a type error for non-array inputs like unknown (as required by the @ts-expect-error test case).
• We use a conditional type with infer to pattern-match the tuple: [infer _First, ...infer Rest] destructures the tuple into the first element and all remaining elements.
• If the pattern matches (the tuple has at least one element), we return Rest -- the tuple with the first element removed.
• If the pattern does not match (the tuple is empty []), we return [].

An alternative approach using variadic tuple types:

type Shift<T extends unknown[]> = T extends [unknown, ...infer Rest]
  ? Rest
  : []

This version skips naming the first element entirely since we do not need it, using unknown as a placeholder instead.

This challenge helps you understand tuple type destructuring with conditional inference and how to apply this concept in real-world scenarios.