Variadic Tuple Types

Variadic Tuple Types: working example

Run this standalone example after compiling with TypeScript 5.4+ in strict mode, targeting ES2022. Expected result: The program prints 7 true; result retains the tuple type [number, boolean].

function tail<T extends unknown[]>(items: [unknown, ...T]): T {
  const [, ...rest] = items;
  return rest;
}
const input: [string, number, boolean] = ["header", 7, true];
const result = tail(input);
const count: number = result[0];
const enabled: boolean = result[1];
console.log(count, enabled);

1. Expected result: The program prints 7 true; result retains the tuple type [number, boolean].
2. The first unknown slot is removed while T captures all remaining positions.
3. Unlike a broad array union, the resulting tuple remembers which position is numeric.