TypeScript Tuple to Union Type

In TypeScript, it's often useful to derive type information from existing data structures. This challenge focuses on transforming a specific type of data structure – a tuple – into a union of its constituent types. This is a common pattern in advanced TypeScript for creating more flexible and expressive types.

Problem Description

Your task is to create a TypeScript type utility called TupleToUnion<T> that takes a tuple type T as input and returns a new type that is a union of all the types present in that tuple.

Key Requirements:

• The utility should accept any tuple type.
• It should correctly extract each element's type from the tuple.
• It should combine these extracted types into a single union type.

Expected Behavior:

If you have a tuple type like [string, number, boolean], TupleToUnion<[string, number, boolean]> should resolve to string | number | boolean.

Edge Cases to Consider:

• Empty tuples: What should TupleToUnion<[]> resolve to?
• Tuples with repeated types: The union should still represent each unique type only once (e.g., [string, string, number] should result in string | number).

Examples

Example 1:

Input: [string, number]
Output: string | number

Explanation: The input is a tuple type with string and number. The output is a union of these two types.

Example 2:

Input: [boolean, null, undefined, string]
Output: boolean | null | undefined | string

Explanation: The input tuple contains four distinct types. The output is the union of all these types.

Example 3:

Input: [1, 2, 3, 2, 1]
Output: 1 | 2 | 3

Explanation: Even though 1 and 2 appear multiple times in the input tuple, the resulting union type only includes each unique number type once.

Example 4:

Input: []
Output: never

Explanation: An empty tuple has no elements, so there are no types to form a union with. The never type is the appropriate representation for a value that will never occur.

Constraints

• The solution must be a generic TypeScript type.
• No runtime code is expected; this is purely a type-level manipulation.

Notes

Consider how TypeScript's built-in features can help you iterate over the elements of a tuple type and combine their types. Think about the distributive property of conditional types, although it might not be directly needed for this specific solution. The never type is the bottom type in TypeScript, representing values that can never occur. It's often the correct result for operations that cannot produce a value or type from an empty input.