added file suffix and check

src/Main.hs

@@ -16,24 +16,39 @@ import           Data.List.Extra             (isSuffixOf)
 
 import Compiler (compile)
 import Renamer.Renamer (rename)
-import           System.Directory            (createDirectory, doesPathExist,
+import System.Directory (
+    createDirectory,
+    doesPathExist,
     getDirectoryContents,
     removeDirectoryRecursive,
-                                              setCurrentDirectory)
+    setCurrentDirectory,
+ )
 import System.Environment (getArgs)
-import           System.Exit                 (ExitCode, exitFailure,
-                                              exitSuccess)
+import System.Exit (
+    ExitCode,
+    exitFailure,
+    exitSuccess,
+ )
 import System.IO (stderr)
-import           System.Process.Extra        (readCreateProcess, shell,
-                                              spawnCommand, waitForProcess)
+import System.Process.Extra (
+    readCreateProcess,
+    shell,
+    spawnCommand,
+    waitForProcess,
+ )
 import TypeChecker.TypeChecker (typecheck)
 
 main :: IO ()
 main =
     getArgs >>= \case
-        [] -> print "Required file path missing"
-        ("-d" : s : _) -> main' True s
-        (s : _) -> main' False s
+        [] -> putStrLn "Required file path missing"
+        ["-d", s] -> do
+            when (".crf" `isSuffixOf` s) (main' True s)
+            putStrLn $ "File '" ++ s ++ "' is not a churf file"
+        [s] -> do
+            when (".crf" `isSuffixOf` s) (main' False s)
+            putStrLn $ "File '" ++ s ++ "' is not a churf file"
+        xs -> putStrLn $ "Can't process: " ++ unwords xs
 
 main' :: Bool -> String -> IO ()
 main' debug s = do

test_program.chf

@@ -26,3 +26,5 @@ bind ma f = case ma of {
     Nothing => Nothing ;
     Just a => f a ;
 };
+
+