The expression return array('Pronamic\W...ESPACE__ . '\Settings') returns the type array<integer,string> which is incompatible with the return type mandated by Pronamic\WordPress\Pay\G...e::get_settings_class() of string.
In the issue above, the returned value is violating the contract defined by the
mentioned interface.
Let's take a look at an example:
interfaceHasName{/** @return string */publicfunctiongetName();}className{public$name;}classUserimplementsHasName{/** @return string|Name */publicfunctiongetName(){returnnewName('foo');// This is a violation of the ``HasName`` interface// which only allows a string value to be returned.}}
In the issue above, the returned value is violating the contract defined by the mentioned interface.
Let's take a look at an example: