Replace First

In this medium-level challenge, you'll implement ReplaceFirst<T, S, R> which replaces the first occurrence of S in a tuple T with R, returning the original tuple if no match is found.

Detailed Explanation

type ReplaceFirst<T extends readonly unknown[], S, R> =
  T extends [infer F, ...infer Rest]
    ? F extends S
      ? [R, ...Rest]
      : [F, ...ReplaceFirst<Rest, S, R>]
    : []

How it works:

• We use conditional types with infer to destructure the tuple into its first element F and the remaining elements Rest.
• If the first element F extends S (matches the search type), we return a new tuple with R replacing F, followed by the unmodified Rest. This ensures only the first occurrence is replaced.
• If F does not match S, we keep F as-is and recursively apply ReplaceFirst to the Rest of the tuple.
• The base case T extends [infer F, ...infer Rest] fails when the tuple is empty, returning [] and stopping the recursion.

This challenge helps you understand recursive tuple manipulation and conditional type inference and how to apply these concepts in real-world scenarios.