1 files changed, 16 insertions, 6 deletions
diff --git a/src/Language/Fiddle/Compiler/Stage2.hs b/src/Language/Fiddle/Compiler/Stage2.hs
index 7306b3f..adf5450 100644
--- a/src/Language/Fiddle/Compiler/Stage2.hs
+++ b/src/Language/Fiddle/Compiler/Stage2.hs
@@ -9,7 +9,7 @@ module Language.Fiddle.Compiler.Stage2 (toStage3) where
 
 import Control.Monad (forM, forM_, unless, when)
 import Control.Monad.Identity (Identity (Identity))
-import Control.Monad.RWS (MonadState (get), MonadWriter (tell), gets, modify')
+import Control.Monad.RWS (MonadState (get, put), MonadWriter (tell), gets, modify')
 import Data.Foldable (Foldable (toList), foldlM)
 import Data.Functor.Identity
 import qualified Data.IntMap as IntMap
@@ -492,13 +492,23 @@ getTypeSize (EnumBitType expr (Identity (EnumBody constants _)) ann) = do
 
   return declaredSize
 
-insertTypeSize :: LocalState -> Identifier f a -> SizeBits -> Compile GlobalState ()
-insertTypeSize (LocalState scopePath) (Identifier s _) size = do
-  modify' $
+diagnosticError :: String -> Annot -> Compile a ()
+diagnosticError str a = tell [Diagnostic Error str (unCommented a)]
+
+insertTypeSize :: LocalState -> Identifier f Annot -> SizeBits -> Compile GlobalState ()
+insertTypeSize (LocalState scopePath) (Identifier s annot) size = do
+  modifyM $
     \(GlobalState globalScope) ->
       let fullName =
             NonEmpty.prependList
               (currentScope scopePath)
               (NonEmpty.singleton (Text.unpack s))
-       in GlobalState $
-            insertScope fullName (Right size) globalScope
+       in case upsertScope fullName (Right size) globalScope of
+            (Just _, _) -> do
+              diagnosticError (printf "Duplicate type %s" s) annot
+              compilationFailure
+            (Nothing, n) -> return $ GlobalState n
+  where
+    modifyM fn = do
+      s <- get
+      put =<< fn s