Hello List! In some of my JSONs I have part "list of any values", for example: [1, "hi", "false", 2.71] To parse it I create type like: data RespItem = forall a. FromJSON a => RespItem { riItem :: [a] } ,------------------------------------------------------------------- | btw, I try `(FromJSON a, Show a, Generic a) => ...` also but don't | see any difference, so I'm not sure what is right constraints list. `------------------------------------------------------------------- And GHC does not allow to derive automatically with "deriving" Show and Generic instances for existential types, as I see. So I write: instance Generic RespItem instance Show RespItem Also this type `RespItem` in part of another one: data Resp = Resp { rHeadings :: [T.Text] , rRow :: [RespItem] } deriving (Generic, Show) Interesting is that now auto-`deriving` works! OK, but I need to to instantiate `FromJSON` for RespItem because next step must be `FromJSON` for Resp. So I'm trying: instance FromJSON RespItem where parseJSON ??? = ??? and here I get different errors, and absolutely don't understand how to parse it, I get "ambiguous type error..." and so on (which is right, sure). === Best regards, Paul