code: private function getLastNonDefaultArgumentIndex(Tokens $tokens, $startIndex, $endIndex)
      {
          for ($i = $endIndex - 1; $i > $startIndex; --$i) {
              $token = $tokens[$i];
  
              if ($token->equals('=')) {
                  $i = $tokens->getPrevMeaningfulToken($i);
  
                  continue;
              }
  
              if ($token->isGivenKind(T_VARIABLE) && !$this->isEllipsis($tokens, $i)) {
                  return $i;
              }
          }
      }
docs: @param Tokens $tokens
  @param int    $startIndex
  @param int    $endIndex
  
  @return null|int