"We are out of raspberries."
Translation:Hallonen är slut.
Because "slut" is uninflected -- it doesn't change for gender/number.
Is this referring to if it was on a sign or in a store? If not, why is "we" assumed.
It could very well be. It could also be that we as e.g. our household are out of raspberries, just like the other day when I was making some waffles only to find out that my wife had eaten all of our berries. At least there was some maple syrup left for me.
I'm guessing that the we is an effort to use a standard expression with which people are generally familiar. The verb vara slut means that there are none left, but English lacks a good verb for this. And "there are no more raspberries" doesn't quite work for pedagogical reasons, since the translation for that into Swedish would be "det finns inga fler hallon".
One of the owlmods could probably add to the discussion or correct me if needed.
I agree with what you're saying. I wrote something about this in another forum, in that case, specifically about why the thing we're out of is indeterminate in the Swedish construction, but determinate in the English: https://www.duolingo.com/comment/6058122
If we were for instance in a store that was out of raspberries we could still say Hallonen är slut, but it would be They are out of raspberries in English. So as you said, we just picked the most standard expression.
Why is it literally translated as "The raspberries are stop"? Is that common phrasing in Swedish?