The expression return new Zgabievi\Kend...st())->filter($builder) returns the type Illuminate\Database\Eloquent\Builder which is incompatible with the return type mandated by Illuminate\Database\Eloquent\Scope::apply() of void.
In the issue above, the returned value is violating the contract defined by the
mentioned interface.
Let's take a look at an example:
interfaceHasName{/** @return string */publicfunctiongetName();}className{public$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: