00ba8b3ac0
We currently still handle immediate return values a lot like non-immediate ones. We provide a slot for them and store them into memory, often just to immediately load them again. To improve this situation, trans_call_inner has to return a Result which contains the immediate return value. Also, it also needs to accept "No destination" in addition to just SaveIn and Ignore. Since "No destination" isn't something that fits well into the Dest type, I've chosen to simply use Option<Dest> instead, paired with an assertion that checks that "None" is only allowed for immediate return values.