Correct return type of methods

[mage2pratik]

Description

Correct return type of methods.

Fixed Issues (if relevant)

1. Correct return type of methods and typo correction. #15993: Correct return type of methods and typo correction.

Manual testing scenarios

N/A

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-engcom-team]

Hi @mage2pratik. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

• @magento-engcom-team give me test instance - deploy test instance based on PR changes
• @magento-engcom-team give me {$VERSION} instance - deploy vanilla Magento instance

For more details, please, review the Magento Contributor Assistant documentation

[orlangur]

Fix PHPDocs of all implementations as well.

[orlangur]

Sorry, I meant https://github.com/magento/magento2/blame/2.2-develop/app/code/Magento/CatalogSearch/Model/ResourceModel/Engine.php#L123 and it is already fixed. Should pull changes for 2.2-develop more frequently to my local.

[magento-engcom-team]

Hi @orlangur, thank you for the review.
ENGCOM-2458 has been created to process this Pull Request

[magento-engcom-team]

Hi @mage2pratik. Thank you for your contribution.
We will aim to release these changes as part of 2.2.6.
Please check the release notes for final confirmation.

Please, consider to port this solution to 2.3 release line.
You may use Porting tool to port commits automatically.