Gives 'non-exhaustive pattern' in Basic at Console

ListItem.hs

listItemAttrDyn False =
  "class" =: "list-item"
listItemAttrDyn True =
  "class" =: "list-item highlight"
  

listItem :: (MonadWidget t m) => (String -> String) -> m (ListItem t)            
listItem mkUrl = do
  rec highlightDyn <- foldDyn (\a _ -> a) False highlightE
      itemAttributesDyn <- mapDyn listItemAttrDyn highlightDyn
      (li, deleteBtn) <- elDynAttr' "li" itemAttributesDyn $ do
        el "span" $ do
          text "UUID"
        el "span" $ do
          text "Label"
        el "span" $ do
          button "Delete"
      let mouseOverE = fmap (const True) $ domEvent Mouseover li
      let mouseOutE = fmap (const False) $ domEvent Mouseout li
      let highlightE = mergeWith (\ _ _ -> True) [mouseOverE, mouseOutE]
  return $ ListItem {
    listItemClick = fmap (const $ mkUrl "/create") $ domEvent Click li
  , listItemDelete = fmap (const $ mkUrl "/delete") deleteBtn
  }