I'm new to both Haskell and gi, and trying to follow GTK+ documentation which is provided as devhelp program. I wrote this trivial program and it is compiled with no errors:

{-# LANGUAGE OverloadedStrings, OverloadedLabels #-}
module Main where
  
import qualified Data.Text as T
import System.Environment (getProgName, getArgs)

import qualified GI.Gio as Gio
import qualified GI.Gtk as Gtk
import Data.GI.Base

activateApp :: {- Gtk.Application -> -} IO ()
activateApp {- app -} = do
  appWindow <- new Gtk.ApplicationWindow [ #title := "Deneme" ] 
  -- on appWindow #close Gtk.widgetDestroy
  #showAll appWindow 
  return ()

main :: IO ()
main = do

  progName <- getProgName
  args <- getArgs

  app <- Gtk.applicationNew (Just "deneme") [ Gio.ApplicationFlagsFlagsNone ]

  on app #startup activateApp
  
  status <- Gio.applicationRun app $ Just $ map T.pack args

  return ()

when I tried to run it, I got this message:
first-gtk-trial.EXE:5092): Gtk-CRITICAL **: gtk_application_new: assertion 'application_id == NULL || g_application_id_is_valid (application_id)' failed
first-gtk-trial.EXE: Received unexpected nullPtr in "applicationNew".
This is a bug in the introspection data, please report it at
https://github.com/haskell-gi/haskell-gi/issues
CallStack (from HasCallStack):
checkUnexpectedReturnNULL, called at .\GI\Gtk\Objects\Application.hs:971:5 in gi-gtk-3.0.21-5hNtKhd2OEL1fcbHMSgHEZ:GI.Gtk.Objects.Application
applicationNew, called at src\Main.hs:24:10 in main:Main

I use stack nigthly build 2018-03-20 on Windows 10/

By the way examples are only for viewing videos etc. Are there any examples which show best practices from ground up?