Laravel5.5 after use php artisan app:name Class not found 1

Solution :

I would suggest looking in your config files, and the main classes which were generated when you started your laravel project (User class, etc) because they are all set to App\User App..... etc.

So for example, in the image you have in the question, it says it can not find App\AppProviders... - This indicates that somewhere you still have a use statement pointed to App\AppProviders.. but you changed the app name, so it's no longer App. 

So if you did not change the app name immediately after starting the project, some of the paths will not be pointing to the correct directories.