Pretty Printing

-- Pretty printing of type expresions
class Pretty p where
  pprint :: (Applicative m, LFresh m) => p -> m Doc

instance Pretty Poly where
  pprint (Poly p) =
    lunbind $
      \ (bindings, typeExpr) ->
        do
          vars <- pprintListSep (pure (PP.text ",")) bindings
          printedExpr <- pprint typeExpr
          pure $ PP.brackets a <+> PP.text "==>" <+> printedExpr

pprintListSep :: forall m. (LFresh m, Pretty a) => m Doc -> [a] -> m Doc
pprintListSep l sep = foldr PP.empty f l
  where
    f a b = do
      a' <- a
      sep' <- sep
      b' <- b
      pure $ a <+> sep <+> b