In https://gerrit.wikimedia.org/r/c/mediawiki/extensions/GrowthExperiments/+/1168603/2/.phan/config.php the new sniff for unused parameters in private methods was disabled to allow for upgrading.
These no-longer used parameters for methods can often just be dropped, but we should double-check first that them being unused is not a bug.
Steps to approach:
- remove te line $cfg['suppress_issue_types'][] = 'PhanUnusedPrivateMethodParameter'; from .phan/config.php
- handle all the phan failures that happen as a result of that