/**
 * @template TKey
 * @template TValue
 */
interface A
{
    /**
     * @phpstan-param array<int, TKey> $keys
     * @phpstan-return A<TKey, TValue>
     */
    public function methodName(...$keys): A;
}

/**
 * @template TKey
 * @template TValue
 * @implements A<TKey, TValue>
 */
class AI implements A
{
    /**
     * @phpstan-param array<int, TKey> $keys
     * @phpstan-return A<TKey, TValue>
     */
    public function methodName(...$keys): A
    {
         // return type of parent method is detected as array<int, TKey> 
    }
}