Intercepted methods returning self are generated with incompatible signature

[sshymko]

Preconditions (*)

• Magento 2.3.1
• Class with pluginized method returning self

Steps to reproduce (*)

1. Extend any class with intercepted methods returning self, for example:
   

   namespace Example\Module\Catalog\Model\Indexer\Category\Product\Action;
   
   class Full extends \Magento\Catalog\Model\Indexer\Category\Product\Action\Full
   {
   
   }

2. Generate interceptors by compiling DI:

   php bin/magento setup:di:compile

3. Locate generated interceptors for descendant classes:

   generated/code/Example/Module/Model/Indexer/Category/Product/Action/Full/Interceptor.php
   

Expected result (*)

1. DI compilation completes successfully
2. Generated interceptor classes are compatible with classes they inherit/intercept

Actual result (*)

1. Return type of the intercepted method is incompatible with the parent:
   
2. PHP Fatal error upon any attempt to use the intercepted descendant class

[m2-assistant]

Hi @sshymko. Thank you for your report.
To help us process this issue please make sure that you provided the following information:

• Summary of the issue
• Information on your environment
• Steps to reproduce
• Expected and actual results

Please make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce. To deploy vanilla Magento instance on our environment, please, add a comment to the issue:

@magento give me 2.3-develop instance - upcoming 2.3.x release

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

@sshymko do you confirm that you were able to reproduce the issue on vanilla Magento instance following steps to reproduce?

• yes
• no

---

• Join Magento Community Engineering Slack and ask your questions in #github channel.

[sshymko]

yes

[Swahjak]

Having the same issue extending Magento\Catalog\Model\Indexer\Category\Product\Action\Full::execute. Magento 2.3.1.

[Swahjak]

Possible duplicate of #11905 and #22769