Showing the user
We have done all the required steps in our architecture to handle and return the errors or throw in case of an exception we didn't handle. But we also have to notify the user. This is of course up to you how you want to do it. The shown example is just one way of doing it but the main thing here is that we most of the time want to notify the user.
In this case, we create a FailureScreen and FailureBody this is because sometimes we want to show a full screen of it and sometimes we just want to show the body. I made these very generic but you are also free to send the Failure object to it as well. The important part here is just showing something to the user so it just doesn't become a blank screen or show text that is not meant for the user to see.
Checking if it is a Failure
Dart has a good keyword called is which is handy for checking types at runtime. Here we know that the object is of type Failure but is you want type-safety for the failure object after checking that it is a type you also have to do something like (e as Failure). which is also defined in the language tour of Dart.