Getting group id from customer session returns wrong data type.

[bydrei]

If you get the customer from the session and then get the group id, the group id is returned as a string. The return type for that function specifies it should be of type int but it is returning as a string.

Preconditions

1. Magento 2.1.12
2. PHP 7.0.27
3. MySQL 5.7.21

Steps to reproduce

$customer = $this->customerSession->getCustomer();
$groupId  = $customer->getGroupId();

Expected result

$groupId should be of type int and not a string.

Actual result

$groupId is returned as a string instead of an int as the function phpDoc specifies.

/**
     * Retrieve customer group identifier
     *
     * @return int
     */
    public function getGroupId()
    {
        if (!$this->hasData('group_id')) {
            $storeId = $this->getStoreId() ? $this->getStoreId() : $this->_storeManager->getStore()->getId();
            $groupId = $this->_scopeConfig->getValue(
                GroupManagement::XML_PATH_DEFAULT_ID,
                ScopeInterface::SCOPE_STORE,
                $storeId
            );
            $this->setData('group_id', $groupId);
        }
        return $this->getData('group_id');
    }

[magento-engcom-team]

@ferrazzuk, thank you for your report.
We've acknowledged the issue and added to our backlog.

[orlangur]

This issue is not valid, see #10519 (comment) for more details.

The return type for that function specifies it should be of type int but it is returning as a string.

Numeric strings are defined as int all over the codebase in fact.