<?php declare(strict_types = 1);

use function PHPStan\Testing\assertType;

/**
 * @template T
 * @param array<T,mixed> $array
 * @return (T is int ? ($array is non-empty-array ? non-empty-list<numeric-string> : list<numeric-string>) : ($array is non-empty-array ? non-empty-list<numeric-string> : list<string>))
*/
function keysAsString(array $array): array
{
	$keys = [];

	foreach ($array as $k => $_) {
		$keys[] = (string)$k;
	}

	return $keys;
}

assertType('array<int, numeric-string>', keysAsString([]));
assertType('non-empty-array<int, numeric-string>', keysAsString(['' => '']));

/**
 * @template N of Num
 * @template _FIZZ of n3|n6|n9|n12
 * @template _BUZZ of n5|n10
 * @template _FIZZBUZZ of n15
 * @param N $n
 * @return ($n is _FIZZBUZZ ? FizzBuzz : ($n is _BUZZ ? Buzz : ($n is _FIZZ ? Fizz : N)))
 */
function fizzbuzz(Num $n)
{
    return match($n % 3) {
        0 => match($n % 5) {
            0 => new FizzBuzz,
            default => new Fizz,
        },
        default => match($n % 5) {
            0 => new Buzz,
            default => $n,
        },
    };
}