Confirmation that (inner) classes are still not fully supported in @AuraEnabled methods?

When writing a controller for a Lightning Component, it is convenient to add the data transfer object classes as inner classes of the controller. This works fine for sending data to the client but I get a gack that includes a java.lang.UnsupportedOperationException when sending from client to server:

An internal server error has occurred\nError ID: 2066801247-4851
(-1600101374)\n\norg.auraframework.throwable.AuraExecutionException:
apex://LifePaymentsController:
java.lang.UnsupportedOperationException\n\tat
.(apex://LifePaymentsController)\n\tat
ui.services.facades.CoreLightningComponentFacadeImpl.runApexAction(CoreLightningComponentFacadeImpl.java:233) …

Here is what the server-side looks like (the save1 method fails):

public class SaveRequest {
    @AuraEnabled public Payee[] newPayees;
    @AuraEnabled public Payment[] payments;
}

...

// Fails
@AuraEnabled
public static void save1(SaveRequest saveRequest) {
    System.debug(JSON.serializePretty(saveRequest));
}

// Works
@AuraEnabled
public static void save2(String jsonString) {
    SaveRequest r = (SaveRequest) JSON.deserializeStrict(jsonString, SaveRequest.class);
    System.debug(JSON.serializePretty(r));
}

and the client-side:

// Fails
var action = servicesComponent.get("c.save1")
action.setParams({ 
    "saveRequest": saveRequest
});

// Works
var action = servicesComponent.get("c.save2");
action.setParams({ 
    "jsonString": JSON.stringify(saveRequest)
});

The save2 alternative method (where deserialization is explicitly coded) works.

I interpret these results to mean that inner classes are still (April 2017) not fully supported in @AuraEnabled methods. Is that the case?

Answer

Attribution
Source : Link , Question Author : Keith C , Answer Author : Fabien Taillon