Type-safe zipping with TypeScript

zip-heterogeneous.ts

declare function zip<T extends readonly unknown[] | [unknown], U extends readonly unknown[] | [unknown]>(
  left: T,
  right: U & { length: T['length'] }): {
  [K in keyof T & keyof U]: [T[K], U[K]]
}

zip([1, 2], ['one', 'two']);
zip([1, 2] as const, ['one', 'two'] as const);
                     
zip([1, 2, 3], ['one', 'two']); // Compile-time error

zip-homogeneous.ts

declare function zip<T extends unknown[] | [unknown], U extends unknown[] | [unknown]>(
  left: T,
  right: T & { length: T['length'] }): {
  [K in keyof T]: [T[K], T[K]]
}

zip([1, 2, 3], [4, 5]); // Compile-time error