Tried solving bug, failed, added todo message, fixed printing

src/Renamer/Renamer.hs

@@ -5,18 +5,27 @@ module Renamer.Renamer (rename) where
 
 import Auxiliary (mapAccumM)
 import Control.Applicative (Applicative (liftA2))
-import           Control.Monad.Except (ExceptT, MonadError (throwError),
-                                       runExceptT)
-import           Control.Monad.State  (MonadState, State, evalState, gets,
-                                       mapAndUnzipM, modify)
+import Control.Monad.Except (
+    ExceptT,
+    MonadError (throwError),
+    runExceptT,
+ )
+import Control.Monad.State (
+    MonadState,
+    State,
+    evalState,
+    gets,
+    mapAndUnzipM,
+    modify,
+ )
 import Data.Function (on)
 import Data.Map (Map)
-import qualified Data.Map             as Map
+import Data.Map qualified as Map
 import Data.Maybe (fromMaybe)
 import Data.Tuple.Extra (dupe, second)
 import Grammar.Abs
 import Grammar.ErrM (Err)
-
+import Grammar.Print (printTree)
 
 -- | Rename all variables and local binds
 rename :: Program -> Err Program
@@ -25,11 +34,11 @@ rename (Program defs) = Program <$> renameDefs defs
 initCxt :: Cxt
 initCxt = Cxt 0 0
 
-data Cxt = Cxt { var_counter  :: Int
+data Cxt = Cxt
+    { var_counter :: Int
     , tvar_counter :: Int
     }
 
-
 -- | Rename monad. State holds the number of renamed names.
 newtype Rn a = Rn {runRn :: ExceptT String (State Cxt) a}
     deriving (Functor, Applicative, Monad, MonadState Cxt, MonadError String)
@@ -60,47 +69,40 @@ renameDefs defs = evalState (runExceptT (runRn $ mapM renameDef defs)) initCxt
             collectTVars tvars = \case
                 TAll tvar t -> collectTVars (tvar : tvars) t
                 TData _ _ -> pure tvars
-              _           -> throwError ("Bad data type definition: " ++ show typ)
+                _ -> throwError ("Bad data type definition: " ++ printTree typ)
 
     renameInj :: [(TVar, TVar)] -> Inj -> Inj
     renameInj new_types (Inj name typ) =
         Inj name $ substituteTVar new_types typ
 
-
 substituteTVar :: [(TVar, TVar)] -> Type -> Type
 substituteTVar new_names typ = case typ of
     TLit _ -> typ
-
-    TVar tvar | Just tvar' <- lookup tvar new_names
-              -> TVar tvar'
-              | otherwise
-              -> typ
-
+    TVar tvar
+        | Just tvar' <- lookup tvar new_names ->
+            TVar tvar'
+        | otherwise ->
+            typ
     TFun t1 t2 -> on TFun substitute' t1 t2
-
-    TAll tvar t | Just tvar' <- lookup tvar new_names
-                -> TAll tvar' $ substitute' t
-                | otherwise
-                -> TAll tvar $ substitute' t
-
+    TAll tvar t
+        | Just tvar' <- lookup tvar new_names ->
+            TAll tvar' $ substitute' t
+        | otherwise ->
+            TAll tvar $ substitute' t
     TData name typs -> TData name $ map substitute' typs
     _ -> error ("Impossible " ++ show typ)
   where
     substitute' = substituteTVar new_names
 
-
 renameExp :: Names -> Exp -> Rn (Names, Exp)
 renameExp old_names = \case
     EVar (LIdent n) -> pure (old_names, EVar . LIdent . fromMaybe n $ Map.lookup n old_names)
     EInj (UIdent n) -> pure (old_names, EInj . UIdent . fromMaybe n $ Map.lookup n old_names)
-
     ELit lit -> pure (old_names, ELit lit)
-
     EApp e1 e2 -> do
         (env1, e1') <- renameExp old_names e1
         (env2, e2') <- renameExp old_names e2
         pure (Map.union env1 env2, EApp e1' e2')
-
     EAdd e1 e2 -> do
         (env1, e1') <- renameExp old_names e1
         (env2, e2') <- renameExp old_names e2
@@ -113,12 +115,10 @@ renameExp old_names = \case
         (new_names'', rhs') <- renameExp new_names' rhs
         (new_names''', e') <- renameExp new_names'' e
         pure (new_names''', ELet (Bind name' vars' rhs') e')
-
     EAbs par e -> do
         (new_names, par') <- newNameL old_names par
         (new_names', e') <- renameExp new_names e
         pure (new_names', EAbs par' e')
-
     EAnn e t -> do
         (new_names, e') <- renameExp old_names e
         t' <- renameTVars t
@@ -147,7 +147,6 @@ renamePattern ns p = case p of
     PVar name -> second PVar <$> newNameL ns name
     _ -> return (ns, p)
 
-
 renameTVars :: Type -> Rn Type
 renameTVars typ = case typ of
     TAll tvar t -> do
@@ -157,24 +156,25 @@ renameTVars typ = case typ of
     TFun t1 t2 -> liftA2 TFun (renameTVars t1) (renameTVars t2)
     _ -> pure typ
 
-substitute :: TVar  -- α
-           -> TVar  -- α_n
-           -> Type  -- A
-           -> Type  -- [α_n/α]A
+substitute ::
+    TVar -> -- α
+    TVar -> -- α_n
+    Type -> -- A
+    Type -- [α_n/α]A
 substitute tvar1 tvar2 typ = case typ of
     TLit _ -> typ
-    TVar tvar | tvar == tvar1   -> TVar tvar2
+    TVar tvar
+        | tvar == tvar1 -> TVar tvar2
         | otherwise -> typ
     TFun t1 t2 -> on TFun substitute' t1 t2
-    TAll tvar t | tvar == tvar1 -> TAll tvar2 $ substitute' t
+    TAll tvar t
+        | tvar == tvar1 -> TAll tvar2 $ substitute' t
         | otherwise -> TAll tvar $ substitute' t
     TData name typs -> TData name $ map substitute' typs
     _ -> error "Impossible"
   where
     substitute' = substitute tvar1 tvar2
 
-
-
 -- | Create multiple names and add them to the name environment
 newNamesL :: Names -> [LIdent] -> Rn (Names, [LIdent])
 newNamesL = mapAccumM newNameL
@@ -185,7 +185,6 @@ newNameL env (LIdent old_name) = do
     new_name <- makeName old_name
     pure (Map.insert old_name new_name env, LIdent new_name)
 
-
 -- | Create multiple names and add them to the name environment
 newNamesU :: Names -> [UIdent] -> Rn (Names, [UIdent])
 newNamesU = mapAccumM newNameU
@@ -196,7 +195,6 @@ newNameU env (UIdent old_name) = do
     new_name <- makeName old_name
     pure (Map.insert old_name new_name env, UIdent new_name)
 
-
 -- | Annotate name with number and increment the number @prefix ⇒ prefix_number@.
 makeName :: String -> Rn String
 makeName prefix = do

src/TypeChecker/TypeCheckerHm.hs

@@ -27,8 +27,11 @@ import Grammar.Abs
 import Grammar.Print (printTree)
 import TypeChecker.TypeCheckerIr qualified as T
 
+-- TODO: Save all substition sets encountered in the program and apply
+--       to all top level functions in the end.
+
 initCtx = Ctx mempty
-initEnv = Env 0 'a' mempty mempty mempty "" mempty mempty
+initEnv = Env 0 'a' mempty mempty mempty "" mempty mempty mempty
 
 run :: Infer a -> Either Error a
 run = run' initEnv initCtx
@@ -53,8 +56,8 @@ checkPrg :: Program -> Infer (T.Program' Type)
 checkPrg (Program bs) = do
     preRun bs
     bs <- checkDef bs
-    sub <- solveUndecidable
-    bs <- mapM (mono sub) bs
+    sub0 <- solveUndecidable
+    bs <- mapM (mono sub0) bs
     return $ T.Program bs
 
 mono :: Subst -> T.Def' Type -> Infer (T.Def' Type)
@@ -74,11 +77,19 @@ preRun (x : xs) = case x of
             >>= flip
                 when
                 ( uncatchableErr $ Aux.do
-                    "Duplicate signatures for function"
+                    "Duplicate signatures of function"
                     quote $ printTree n
                 )
         insertSig (coerce n) (Just t) >> preRun xs
     DBind (Bind n _ e) -> do
+        binds <- gets declaredBinds
+        when
+            (coerce n `S.member` binds)
+            ( uncatchableErr $ Aux.do
+                "Duplicate declarations of function"
+                quote $ printTree n
+            )
+        modify (\st -> st{declaredBinds = S.insert (coerce n) st.declaredBinds})
         collect (collectTVars e)
         s <- gets sigs
         case M.lookup (coerce n) s of
@@ -105,12 +116,12 @@ checkBind :: Bind -> Infer (T.Bind' Type)
 checkBind bind@(Bind name args e) = do
     setCurrentBind $ coerce name
     let lambda = makeLambda e (reverse (coerce args))
-    (e, lambda_t) <- inferExp lambda
+    (sub0, (e, lambda_t)) <- inferExp lambda
     s <- gets sigs
     case M.lookup (coerce name) s of
         Just (Just t') -> do
             sub1 <- bindErr (unify lambda_t (skolemize t')) bind
-            return $ T.Bind (coerce name, apply sub1 t') [] (e, lambda_t)
+            return $ T.Bind (coerce name, apply (sub1 `compose` sub0) t') [] (e, lambda_t)
         _ -> do
             insertSig (coerce name) (Just lambda_t)
             return (T.Bind (coerce name, lambda_t) [] (e, lambda_t))
@@ -178,12 +189,12 @@ returnType :: Type -> Type
 returnType (TFun _ t2) = returnType t2
 returnType a = a
 
-inferExp :: Exp -> Infer (T.ExpT' Type)
+inferExp :: Exp -> Infer (Subst, T.ExpT' Type)
 inferExp e = do
     (s, (e', t)) <- algoW e
     let subbed = apply s t
     modify (\st -> st{undecidedSigs = apply s st.undecidedSigs})
-    return (e', subbed)
+    return (s, (e', subbed))
 
 class CollectTVars a where
     collectTVars :: a -> Set T.Ident
@@ -851,6 +862,7 @@ data Env = Env
     , currentBind :: T.Ident
     , undecidedSigs :: Map T.Ident Type
     , toDecide :: Set T.Ident
+    , declaredBinds :: Set T.Ident
     }
     deriving (Show)