Backpack\CRUD\app\Librar...neratorInterface::class of type string is incompatible with the type boolean expected by parameter $autoload of class_implements().
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Ignorable by Annotation
)
If this is a false-positive, you can also ignore this issue in your code via the ignore-type annotation
The expression return is_callable($this...this) : $this->fileName also could return the type Closure which is incompatible with the documented return type string.