not working.purs

data ShowProps = ShowProps (forall sym. IsSymbol sym => SProxy sym -> String)

instance showProps ::
  (Show a, IsSymbol sym) =>
  FoldingWithIndex (ShowProps) (SProxy sym) String a String where
  foldingWithIndex (ShowProps fn) prop str a =
    pre <> fn prop <> ": " <> show a
    where
    pre | str == "" = ""
        | otherwise = str <> ", "

showRecord :: forall r sym.
  IsSymbol sym =>
  HFoldlWithIndex (ShowProps) String { | r } String =>
  (forall sym2. IsSymbol sym2 => SProxy sym2 -> String) ->
  { | r } ->
  String
showRecord fn r =
  "{ " <> hfoldlWithIndex (ShowProps fn) "" r <> " }"

bu ::
  forall sym a.
  FoldingWithIndex ShowProps (SProxy sym) String a String =>
  String
bu = showRecord reflectSymbol' { a: "foo", b: 1 }
  where
    reflectSymbol' :: forall sym2. IsSymbol sym2 => SProxy sym2 -> String
    reflectSymbol' = reflectSymbol
    -- No type class instance was found for IsSymbol t0