Errors when using SplFileObject in a Hack class

hack-splfileojbect

<?hh
 function test_splfile(string $file_name) : void
{
 $file1 = new SplFileObject($file_name);

 // These loops work fine
foreach ($file1 as $line_number => $text) { /* hhvm: Could not find method key in an object of
                                               type SplFileObject Typing[4053]) */
     echo $text . "\n" . $line_number;
 } 

 $file1->rewind();
 
 while ($file1->valid()) {

    $key = $file1->key();
    $value = $file1->current();

    $file1->next();
 }       
}

class test  {

   protected SplFileObject $file2; // It is incompatible with an object of type SplFileObject

   public function __construct($file_name)
   {
       $this->file2 = new \SplFileObject($file_name);
   }

    public function test_bug() : void
    {
// Invalid foreach (Typing[4110])
// This is an object of type KeyedTraversable because this is used in a foreach statement
       foreach ($this->file2 as $line_number => $text) {            
           echo $text . "\n" . $line_number;
       } 

       $this->file2->rewind();
        
       while ($this->file2->valid()) {
       
          $key = $this->file2->key(); // Could not find method key in an object of type SplFileObject (Typing[4053])
                     //  /tmp/hh_server/hhi_3666eaf1/stdlib/builtins_spl.hhi:97:7,19: Declaration of SplFileObject is here
          $value = $this->file2->current();
          
          $this->file2->next();
       } 
    }
}