the specified line reads:
if (!\in_array('Drupal\views_bulk_operations\Action\ViewsBulkOperationsActionInterface', \class_implements($definition['class']))) {
the problem seems to be that 'class_implement()' can also return FALSE, when class not implements. Thus give the wrong type to 'in_array'
Not sure how to reproduce
Check whether if( \class_implements() !== FALSE)
create patch
Closed: works as designed
4.1
Core
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
I understand and appreciate the reasons for closing this ticket.
In case it helps anyone stumbling across this problem in future:
I experienced this problem due to a typo in the namespace of my custom action class file.
My advice would be to check the namespace, and also to check that your class name matches the filename of your action class.