Recursive newtype in not deriving

[wclr]

Here is a simple modified example from docs with recursive newtype, and it is not deriving:

newtype AppUser = AppUser { name :: String, age :: Maybe Int, appUser :: AppUser }

derive instance newtypeAppUser :: Newtype AppUser _

derive newtype instance decodeJsonAppUser :: DecodeJson AppUser -- error

The value of decodeJsonAppUser is undefined here, so this reference is not allowed.
PureScript(CycleInDeclaration)

If it works as intended, probably it worth mentioning in the docs.

[garyb]

There's an issue open for this on the compiler repo: purescript/purescript#3407. Closing this one as it's not the library's fault.