AccessResult::orIf

public AccessResult::orIf(AccessResultInterface $other)

  |A N F
--+-----
A |A A F
N |A N F
F |F F F

public function orIf(AccessResultInterface $other) {
  $merge_other = FALSE;
  // $other's cacheability metadata is merged if $merge_other gets set to TRUE
  // and this happens in three cases:
  // 1. $other's access result is the one that determines the combined access
  //    result.
  // 2. This access result is not cacheable and $other's access result is the
  //    same. i.e. attempt to return a cacheable access result.
  // 3. Neither access result is 'forbidden' and both are cacheable: inherit
  //    the other's cacheability metadata because it may turn into a
  //    'forbidden' for another value of the cache contexts in the
  //    cacheability metadata. In other words: this is necessary to respect
  //    the contagious nature of the 'forbidden' access result.
  //    e.g. we have two access results A and B. Neither is forbidden. A is
  //    globally cacheable (no cache contexts). B is cacheable per role. If we
  //    don't have merging case 3, then A->orIf(B) will be globally cacheable,
  //    which means that even if a user of a different role logs in, the
  //    cached access result will be used, even though for that other role, B
  //    is forbidden!
  if ($this->isForbidden() || $other->isForbidden()) {
    $result = static::forbidden();
    if (!$this->isForbidden() || ($this->getCacheMaxAge() === 0 && $other->isForbidden())) {
      $merge_other = TRUE;
    }
  }
  elseif ($this->isAllowed() || $other->isAllowed()) {
    $result = static::allowed();
    if (!$this->isAllowed() || ($this->getCacheMaxAge() === 0 && $other->isAllowed()) || ($this->getCacheMaxAge() !== 0 && $other instanceof CacheableDependencyInterface && $other->getCacheMaxAge() !== 0)) {
      $merge_other = TRUE;
    }
  }
  else {
    $result = static::neutral();
    if (!$this->isNeutral() || ($this->getCacheMaxAge() === 0 && $other->isNeutral()) || ($this->getCacheMaxAge() !== 0 && $other instanceof CacheableDependencyInterface && $other->getCacheMaxAge() !== 0)) {
      $merge_other = TRUE;
    }
  }
  $result->inheritCacheability($this);
  if ($merge_other) {
    $result->inheritCacheability($other);
  }
  return $result;
}