Added proper error message to monomorphizer; made subst a monoid

src/Main.hs

@@ -144,7 +144,7 @@ main' opts s =
             when opts.logIL (printToErr "\n-- Lambda Lifter --" >> log lifted)
 
 
-            let monomorphized = monomorphize lifted
+            monomorphized <- fromErr $ monomorphize lifted
             when opts.logIL (printToErr "\n -- Monomorphizer --" >> log monomorphized)
 
 

src/Monomorphizer/Monomorphizer.hs

@@ -28,7 +28,7 @@ module Monomorphizer.Monomorphizer (monomorphize, morphExp, morphBind) where
 
 
 import           Control.Monad.Reader          (MonadReader (ask, local),
-                                                Reader, asks, runReader)
+                                                ReaderT, asks, runReaderT)
 import           Control.Monad.State           (MonadState,
                                                 StateT (runStateT), gets,
                                                 modify)
@@ -38,22 +38,20 @@ import           Grammar.Print                 (printTree)
 import           Monomorphizer.DataTypeRemover (removeDataTypes)
 import qualified Monomorphizer.MonomorphizerIr as O
 import qualified Monomorphizer.MorbIr          as M
--- import TypeChecker.TypeCheckerIr (Ident (Ident))
 import           LambdaLifterIr                (Ident (..))
--- import TypeChecker.TypeCheckerIr qualified as T
 import qualified LambdaLifterIr                as L
 
 import           Data.Maybe                    (fromJust, catMaybes)
 import           Data.Tuple.Extra              (secondM)
-import Debug.Trace (trace)
+import Control.Monad.Except (throwError, Except, runExcept, MonadError)
-import Test.QuickCheck.State (State(expected))
+import Data.List (foldl')
 
 {- | EnvM is the monad containing the read-only state as well as the
 output state containing monomorphized functions and to-be monomorphized
 data type declarations.
 -}
-newtype EnvM a = EnvM (StateT Output (Reader Env) a)
+newtype EnvM a = EnvM (StateT Output (ReaderT Env (Except String)) a)
-    deriving (Functor, Applicative, Monad, MonadState Output, MonadReader Env)
+    deriving (Functor, Applicative, Monad, MonadState Output, MonadReader Env, MonadError String)
 
 type Output = Map.Map Ident Outputted
 
@@ -106,25 +104,26 @@ isConsMarked ident = gets (Map.member ident)
 
 -- | Finds main bind.
 getMain :: EnvM L.Bind
-getMain = asks (\env -> case Map.lookup (Ident "main") (input env) of
+getMain = do
-                          Just mainBind -> mainBind
+    env <- ask
-                          Nothing -> error "main not found in monomorphizer!"
+    case Map.lookup (Ident "main") (input env) of
-                        )
+          Just mainBind -> return mainBind
+          Nothing -> throwError "main not found in monomorphizer!"
 
 {- | Makes a kv pair list of polymorphic to monomorphic mappings, throws runtime
 error when encountering different structures between the two arguments. Debug:
 First argument is the name of the bind.
 -}
-mapTypes :: Ident -> L.Type -> M.Type -> [(Ident, M.Type)]
+mapTypes :: Ident -> L.Type -> M.Type -> EnvM [(Ident, M.Type)]
-mapTypes _ident (L.TLit _) (M.TLit _) = []
+mapTypes _ident (L.TLit _) (M.TLit _) = return []
-mapTypes _ident (L.TVar (L.MkTVar i1)) tm = [(i1, tm)]
+mapTypes _ident (L.TVar (L.MkTVar i1)) tm = return [(i1, tm)]
 mapTypes ident (L.TFun pt1 pt2) (M.TFun mt1 mt2) =
-    mapTypes ident pt1 mt1
+    (++) <$> mapTypes ident pt1 mt1 <*> mapTypes ident pt2 mt2
-        ++ mapTypes ident pt2 mt2
 mapTypes ident (L.TData tIdent pTs) (M.TData mIdent mTs) =
     if tIdent /= mIdent
-        then error "the data type names of monomorphic and polymorphic data types does not match"
+        then throwError "the data type names of monomorphic and polymorphic data types does not match"
-        else foldl (\xs (p, m) -> mapTypes ident p m ++ xs) [] (zip pTs mTs)
+        else foldl' (\xs (p, m) -> do x <- mapTypes ident p m; (++x) <$> xs) (return []) (zip pTs mTs)
+-- This is a proper callstack error as a previous phase has a bug.
 mapTypes ident t1 t2 = error $ "in bind: '" ++ printTree ident ++ "', " ++
   "structure of types not the same: '" ++ printTree t1 ++ "', '" ++ printTree t2 ++ "'"
 
@@ -166,11 +165,12 @@ morphBind expectedType b@(L.Bind (ident, btype) args (exp, expt)) = do
     -- The "new name" is used to find out if it is already marked or not.
     let name' = newFuncName expectedType b
     bindMarked <- isBindMarked name'
+    mt <- mapTypes ident btype expectedType
     local
         ( \env ->
             env
                 { locals = Set.fromList (map fst args)
-                , polys = Map.fromList (mapTypes ident btype expectedType)
+                , polys = Map.fromList mt
                 }
         )
         $ do
@@ -196,11 +196,12 @@ morphBind expectedType b@(L.BindC cxt (ident, btype) args (exp, expt)) = do
     -- The "new name" is used to find out if it is already marked or not.
     let name' = newFuncName expectedType b
     bindMarked <- isBindMarked name'
+    mt <- mapTypes ident btype expectedType
     local
         ( \env ->
             env
                 { locals = Set.fromList (map fst args)
-                , polys = Map.fromList (mapTypes ident btype expectedType)
+                , polys = Map.fromList mt
                 }
         )
         $ do
@@ -234,8 +235,7 @@ morphArg (ident, t) = do
 -- | Gets the data bind from the name of a constructor.
 getInputData :: Ident -> EnvM (Maybe L.Data)
 getInputData ident = do
-    env <- ask
+    asks (Map.lookup ident . dataDefs)
-    return $ Map.lookup ident (dataDefs env)
 
 {- | Monomorphize a constructor using it's global name. Constructors may
 appear as expressions in the tree, or as patterns in case-expressions.
@@ -248,12 +248,13 @@ morphCons expectedType ident newIdent = do
         -- closures can have unbound variables
         Nothing -> pure ()
         Just d -> do
-            modify (\output -> Map.insert newIdent (Data expectedType d) output)
+            modify (Map.insert newIdent (Data expectedType d))
 
 -- | Converts literals from input to output tree.
 convertLit :: L.Lit -> M.Lit
 convertLit (L.LInt v)  = M.LInt v
 convertLit (L.LChar v) = M.LChar v
+convertLit l           = error $ "Unexpected lit in monomorphizer: '" ++ printTree l ++ "'"
 
 
 -- | Monomorphizes an expression, given an expected type.
@@ -292,7 +293,7 @@ morphExp expectedType exp = case exp of
             else do
                 bind <- getInputBind ident
                 case bind of
-                    Nothing -> error $ "unbound variable: '" ++ printTree ident ++ "'"
+                    Nothing -> throwError $ "unbound variable: '" ++ printTree ident ++ "'"
                     Just bind' -> do
                         -- New bind to process
                         newBindName <- morphBind expectedType bind'
@@ -356,8 +357,7 @@ morphPattern p expectedType = case p of
 
 -- Exampel: List a  =>  a -> List a
 convertConsTypeToDataType :: M.Type -> [M.Type] -> M.Type
-convertConsTypeToDataType inner (t:ts) = convertConsTypeToDataType (M.TFun t inner) ts
+convertConsTypeToDataType = foldl (flip M.TFun)
-convertConsTypeToDataType inner []     = inner
 
 
 -- | Creates a new identifier for a function with an assigned type.
@@ -381,28 +381,26 @@ newName t (Ident str) = Ident $ str ++ "$" ++ newName' t
     newName' (M.TData (Ident str) ts) = str ++ foldl (\s t -> s ++ "." ++ newName' t) "" ts
 
 -- | Monomorphization step.
-monomorphize :: L.Program -> O.Program
+monomorphize :: L.Program -> Either String O.Program
-monomorphize (L.Program defs) =
+monomorphize (L.Program defs) = do
-    removeDataTypes $
+    op <- runEnvM Map.empty (createEnv defs) monomorphize'
-        M.Program
+    let prg = getDefsFromOutput op
-            ( getDefsFromOutput
+    return . removeDataTypes $ M.Program prg
-                (runEnvM Map.empty (createEnv defs) monomorphize')
-            )
   where
     monomorphize' :: EnvM ()
     monomorphize' = do
         mainBind <- getMain
         case mainBind of
-          (L.BindC _ _ _ _) -> error "main should not be a BindC node"
+          (L.BindC {}) -> error "main should not be a BindC node"
           main@(L.Bind _ _ (_, mainType)) -> case getMonoFromMono mainType of
-            Nothing -> error "main should be monomorphic"
+            Nothing -> throwError "main should be monomorphic"
             Just mainTypeMono -> do
               morphBind mainTypeMono main
               return ()
 
 -- | Runs and gives the output binds.
-runEnvM :: Output -> Env -> EnvM () -> Output
+runEnvM :: Output -> Env -> EnvM () -> Either String Output
-runEnvM o env (EnvM stateM) = snd $ runReader (runStateT stateM o) env
+runEnvM o env (EnvM stateM) = snd <$> runExcept (runReaderT (runStateT stateM o) env)
 
 -- | Creates the environment based on the input binds.
 createEnv :: [L.Def] -> Env
@@ -485,7 +483,7 @@ createNewData ((consIdent, consType, polyData) : input) o =
 getDataType :: M.Type -> M.Type
 getDataType (M.TFun _t1 t2)     = getDataType t2
 getDataType tData@(M.TData _ _) = tData
-getDataType _                   = error "???"
+getDataType _                   = error "Bug in previous phase of compilation"
 
 
 addLocal :: Ident -> Env -> Env

src/TypeChecker/TypeCheckerHm.hs

@@ -16,7 +16,7 @@ import Control.Monad.State
 import Control.Monad.Writer
 import Data.Coerce (coerce)
 import Data.Function (on)
-import Data.List (foldl', nub)
+import Data.List (foldl')
 import Data.List.Extra (unsnoc)
 import Data.Map (Map)
 import Data.Map qualified as M
@@ -28,14 +28,6 @@ import Grammar.Print (printTree)
 import TypeChecker.TypeCheckerIr (T, T')
 import TypeChecker.TypeCheckerIr qualified as T
 
-{-
-TODO
-Prettifying the types of generated variables does only need to be done when
-presenting the types to the user, i.e, when the user has made a mistake.
-For succesfully typed programs the types only need to match.
-
--}
-
 -- | Type check a program
 typecheck :: Program -> Either String (T.Program' Type, [Warning])
 typecheck = onLeft msg . run . checkPrg
@@ -245,7 +237,7 @@ algoW = \case
                 "does not match inferred type"
                 quote $ printTree t'
             )
-        let comp = sub1 `compose` sub0
+        let comp = sub1 <> sub0
         return (comp, (apply comp e', t))
 
     -- \| ------------------
@@ -309,7 +301,7 @@ algoW = \case
         (s2, (e1', t1)) <- algoW e1
         s3 <- exprErr (unify t0 int) err
         s4 <- exprErr (unify t1 int) err
-        let comp = s4 `compose` s3 `compose` s2 `compose` s1
+        let comp = s4 <> s3 <> s2 <> s1
         return
             ( comp
             , apply comp (T.EAdd (e0', t0) (e1', t1), int)
@@ -327,7 +319,7 @@ algoW = \case
             (s1, (e1', t1)) <- algoW e1
             s2 <- unify (apply s1 t0) (TFun t1 fr)
             let t = apply s2 fr
-            let comp = s2 `compose` s1 `compose` s0
+            let comp = s2 <> s1 <> s0
             return (comp, apply comp (T.EApp (e0', t0) (e1', t1), t))
 
     -- \| Γ ⊢ e₀ : τ, S₀     S₀Γ, x : S̅₀Γ̅(τ) ⊢ e₁ : τ', S₁
@@ -344,7 +336,7 @@ algoW = \case
             let t' = generalize (apply s1 env) t0
             withBinding (coerce name) t' $ do
                 (s2, (e1', t2)) <- algoW e1
-                let comp = s2 `compose` s1
+                let comp = s2 <> s1
                 return
                     ( comp
                     , apply
@@ -354,7 +346,7 @@ algoW = \case
     ECase caseExpr injs -> do
         (sub, (e', t)) <- algoW caseExpr
         (subst, injs, ret_t) <- checkCase t injs
-        let comp = subst `compose` sub
+        let comp = subst <> sub
         return (comp, apply comp (T.ECase (e', t) injs, ret_t))
 
 checkCase :: Type -> [Branch] -> Infer (Subst, [T.Branch' Type], Type)
@@ -367,18 +359,18 @@ checkCase expT brnchs = do
     (sub1, _) <-
         foldM
             ( \(sub, acc) x ->
-                (\a -> (a `compose` sub, a `apply` acc)) <$> unify x acc
+                (\a -> (a <> sub, a `apply` acc)) <$> unify x acc
             )
             (nullSubst, expT)
             branchTs
     (sub2, returns_type) <-
         foldM
             ( \(sub, acc) x ->
-                (\a -> (a `compose` sub, a `apply` acc)) <$> unify x acc
+                (\a -> (a <> sub, a `apply` acc)) <$> unify x acc
             )
             (nullSubst, head returns)
             (tail returns)
-    let comp = sub2 `compose` sub1 `compose` sub0
+    let comp = sub2 <> sub1 <> sub0
     return (comp, apply comp injs, apply comp returns_type)
 
 inferBranch :: Branch -> Infer (Subst, Type, T.Branch' Type, Type)
@@ -463,7 +455,7 @@ unify t0 t1 = case (t0, t1) of
     (TFun a b, TFun c d) -> do
         s1 <- unify a c
         s2 <- unify (apply s1 b) (apply s1 d)
-        return $ s2 `compose` s1
+        return $ s2 <> s1
     (TVar a, t@(TData _ _)) -> return $ singleton a t
     (t@(TData _ _), TVar b) -> return $ singleton b t
     (TVar a, t) -> occurs a t
@@ -575,7 +567,7 @@ fresh :: Infer Type
 fresh = do
     n <- gets count
     modify (\st -> st{count = succ (count st)})
-    return $ TVar $ MkTVar $ LIdent $ show n
+    return . TVar . MkTVar . LIdent $ letters !! n
 
 -- Is the left more general than the right
 (<<=) :: Type -> Type -> Infer Bool
@@ -730,13 +722,15 @@ instance SubstType (T T.Ident Type) where
 nullSubst :: Subst
 nullSubst = mempty
 
--- | Compose two substitution sets
+{- | Compose two substitution sets
+The monoid instance of Subst uses this definition
+-}
 compose :: Subst -> Subst -> Subst
 compose m1@(Subst m1') (Subst m2) = Subst $ M.map (apply m1) m2 `M.union` m1'
 
 -- | Compose a list of substitution sets into one
 composeAll :: [Subst] -> Subst
-composeAll = foldl' compose nullSubst
+composeAll = mconcat
 
 {- | Convert a function with arguments to its pointfree version
 > makeLambda (add x y = x + y) = add = \x. \y. x + y
@@ -914,5 +908,5 @@ uncatchableErr msg = throwError $ Error msg False
 quote :: String -> String
 quote s = "'" ++ s ++ "'"
 
-letters :: [T.Ident]
+letters :: [String]
-letters = map T.Ident $ [1 ..] >>= flip replicateM ['a' .. 'z']
+letters = [1 ..] >>= flip replicateM ['a' .. 'z']

src/TypeChecker/TypeCheckerIr.hs

@@ -60,7 +60,6 @@ newtype TVar = MkTVar Ident
 type T' a t = (a t, t)
 type T a t = (a, t)
 
-
 data Bind' t = Bind (T Ident t) [T Ident t] (T' Exp' t)
     deriving (Eq, Ord, Show, Functor)
 
@@ -74,7 +73,8 @@ instance Print t => Print (Program' t) where
     prt i (Program sc) = prt i sc
 
 instance Print t => Print (Bind' t) where
-    prt i (Bind sig parms rhs) = concatD
+    prt i (Bind sig parms rhs) =
+        concatD
             [ prtSig sig
             , prt i parms
             , doc $ showString "="
@@ -93,7 +93,8 @@ instance (Print a, Print t) => Print (T a t) where
     prt i (x, t) = noT
       where
         noT = prt i x
-        withT = concatD
+        withT =
+            concatD
                 [ doc $ showString "("
                 , prt i x
                 , doc $ showString ":"