Got it, thanks for the clarification! I'm going to close my PR for now anyway since the elm-server will have to be updated if we do make any changes here. If I re-open I'll also make sure I address the issue of memoizing the Prelude.interfaces.

BTW if we do make changes here that require changes in elm-lang, what is the policy on opening PRs on that repo? Could you perhaps merge master on elm-lang with dev so that it's updated? It would make more sense to me to keep Elm/dev in sync with elm-lang/dev, and have the master branches of each repo maintain compatibility as well. Currently elm-lang/dev is behind master so I'm not sure where a PR like this would go. Thanks!