added shadowing for ECase in Renamer
This commit is contained in:
sebastianselander
parent
33b69a1895
commit
24007313cb
2 changed files with 14 additions and 516 deletions
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{-# LANGUAGE LambdaCase #-}
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{-# LANGUAGE OverloadedStrings #-}
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-- | A module for type checking and inference using algorithm W, Hindley-Milner
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module TypeChecker.TypeChecker where
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import Control.Monad.Except
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import Control.Monad.Reader
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import Control.Monad.State
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import Data.Foldable (traverse_)
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import Data.Functor.Identity (runIdentity)
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import Debug.Trace (trace)
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import Data.List (foldl')
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import Data.Map (Map)
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import Data.Map qualified as M
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import Data.Set (Set)
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import Data.Set qualified as S
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import Data.Maybe (fromMaybe)
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import Grammar.Abs
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import Grammar.Print (printTree)
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import TypeChecker.TypeCheckerIr (
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Ctx (..),
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Env (..),
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Error,
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Infer,
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Poly (..),
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Subst,
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)
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import TypeChecker.TypeCheckerIr qualified as T
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initCtx = Ctx mempty
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initEnv = Env 0 mempty mempty
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runPretty :: Exp -> Either Error String
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runPretty = fmap (printTree . fst) . run . inferExp
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run :: Infer a -> Either Error a
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run = runC initEnv initCtx
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runC :: Env -> Ctx -> Infer a -> Either Error a
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runC e c = runIdentity . runExceptT . flip runReaderT c . flip evalStateT e
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typecheck :: Program -> Either Error T.Program
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typecheck = run . checkPrg
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{- | Start by freshening the type variable of data types to avoid clash with
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other user defined polymorphic types
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This might be wrong for type constructors that work over several variables
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-}
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-- freshenData :: Data -> Infer Data
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-- freshenData (Data (Constr name ts) constrs) = do
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-- new_ts <- traverse freshenType ts
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-- new_constrs <- traverse freshenConstr constrs
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-- return $ Data (Constr name new_ts) new_constrs
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--TODO: Fix incorrect behavior here
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{- | Freshen all polymorphic variables, regardless of name
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| freshenType "d" (a -> b -> c) becomes (d -> d -> d)
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-}
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-- freshenType :: Type -> Infer Type
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-- freshenType t = do
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-- let freeVars = (S.toList $ free t)
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-- frs <- sequenceA $ map (const fresh) freeVars
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-- let remaps = M.fromList $ zip freeVars frs
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-- return $ go remaps t
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-- where
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-- go :: Map Ident Type -> Type -> Type
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-- go m t = case t of
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-- TPol a -> fromMaybe (error "bug in \'free\'") (M.lookup a m )
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-- TMono a -> TMono a
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-- TArr t1 t2 -> TArr (go m t1) (go m t2)
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-- TConstr (Constr ident ts) -> TConstr (Constr ident (map (go m) ts))
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-- freshenConstr :: Constructor -> Infer Constructor
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-- freshenConstr (Constructor name t) = do
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-- t' <- freshenType t
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-- return $ Constructor name t'
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checkData :: Data -> Infer ()
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checkData d = do
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case d of
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(Data typ@(Constr name ts) constrs) -> do
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unless
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(all isPoly ts)
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(throwError $ unwords ["Data type incorrectly declared"])
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traverse_
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( \(Constructor name' t') ->
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if TConstr typ == retType t'
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then insertConstr name' t'
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else
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throwError $
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unwords
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[ "return type of constructor:"
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, printTree name
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, "with type:"
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, printTree (retType t')
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, "does not match data: "
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, printTree typ
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]
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)
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constrs
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retType :: Type -> Type
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retType (TArr _ t2) = retType t2
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retType a = a
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checkPrg :: Program -> Infer T.Program
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checkPrg (Program bs) = do
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preRun bs
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bs' <- checkDef bs
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return $ T.Program bs'
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where
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preRun :: [Def] -> Infer ()
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preRun [] = return ()
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preRun (x : xs) = case x of
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DBind (Bind n t _ _ _) -> insertSig n t >> preRun xs
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DData d@(Data _ _) -> checkData d >> preRun xs
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checkDef :: [Def] -> Infer [T.Def]
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checkDef [] = return []
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checkDef (x : xs) = case x of
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(DBind b) -> do
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b' <- checkBind b
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fmap (T.DBind b' :) (checkDef xs)
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(DData d) -> fmap (T.DData d :) (checkDef xs)
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checkBind :: Bind -> Infer T.Bind
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checkBind (Bind n t _ args e) = do
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(t', e') <- inferExp $ makeLambda e (reverse args)
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s <- unify t t'
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let t'' = apply s t
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unless
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(t `typeEq` t'')
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( throwError $
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unwords
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[ "Top level signature"
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, printTree t
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, "does not match body with inferred type:"
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, printTree t''
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]
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)
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return $ T.Bind (n, t) e'
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where
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makeLambda :: Exp -> [Ident] -> Exp
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makeLambda = foldl (flip EAbs)
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{- | Check if two types are considered equal
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For the purpose of the algorithm two polymorphic types are always considered
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equal
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-}
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typeEq :: Type -> Type -> Bool
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typeEq (TArr l r) (TArr l' r') = typeEq l l' && typeEq r r'
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typeEq (TMono a) (TMono b) = a == b
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typeEq (TConstr (Constr name a)) (TConstr (Constr name' b)) =
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length a == length b
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&& name == name'
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&& and (zipWith typeEq a b)
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typeEq (TPol _) (TPol _) = True
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typeEq _ _ = False
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isMoreSpecificOrEq :: Type -> Type -> Bool
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isMoreSpecificOrEq _ (TPol _) = True
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isMoreSpecificOrEq (TArr a b) (TArr c d) =
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isMoreSpecificOrEq a c && isMoreSpecificOrEq b d
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isMoreSpecificOrEq (TConstr (Constr n1 ts1)) (TConstr (Constr n2 ts2)) =
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n1 == n2
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&& length ts1 == length ts2
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&& and (zipWith isMoreSpecificOrEq ts1 ts2)
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isMoreSpecificOrEq a b = a == b
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isPoly :: Type -> Bool
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isPoly (TPol _) = True
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isPoly _ = False
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inferExp :: Exp -> Infer (Type, T.Exp)
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inferExp e = do
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(s, t, e') <- algoW e
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let subbed = apply s t
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return (subbed, replace subbed e')
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replace :: Type -> T.Exp -> T.Exp
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replace t = \case
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T.ELit _ e -> T.ELit t e
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T.EId (n, _) -> T.EId (n, t)
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T.EAbs _ name e -> T.EAbs t name e
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T.EApp _ e1 e2 -> T.EApp t e1 e2
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T.EAdd _ e1 e2 -> T.EAdd t e1 e2
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T.ELet (T.Bind (n, _) e1) e2 -> T.ELet (T.Bind (n, t) e1) e2
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T.ECase _ expr injs -> T.ECase t expr injs
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algoW :: Exp -> Infer (Subst, Type, T.Exp)
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algoW = \case
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-- \| TODO: More testing need to be done. Unsure of the correctness of this
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EAnn e t -> do
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(s1, t', e') <- algoW e
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unless
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(t `isMoreSpecificOrEq` t')
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( throwError $
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unwords
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[ "Annotated type:"
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, printTree t
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, "does not match inferred type:"
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, printTree t'
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]
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)
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applySt s1 $ do
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s2 <- unify t t'
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return (s2 `compose` s1, t, e')
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-- \| ------------------
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-- \| Γ ⊢ i : Int, ∅
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ELit (LInt n) ->
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return (nullSubst, TMono "Int", T.ELit (TMono "Int") (LInt n))
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ELit a -> error $ "NOT IMPLEMENTED YET: ELit " ++ show a
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-- \| x : σ ∈ Γ τ = inst(σ)
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-- \| ----------------------
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-- \| Γ ⊢ x : τ, ∅
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EId i -> do
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var <- asks vars
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case M.lookup i var of
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Just t -> inst t >>= \x -> return (nullSubst, x, T.EId (i, x))
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Nothing -> do
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sig <- gets sigs
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case M.lookup i sig of
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Just t -> return (nullSubst, t, T.EId (i, t))
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Nothing -> do
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constr <- gets constructors
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case M.lookup i constr of
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Just t -> return (nullSubst, t, T.EId (i, t))
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Nothing ->
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throwError $
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"Unbound variable: " ++ show i
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-- \| τ = newvar Γ, x : τ ⊢ e : τ', S
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-- \| ---------------------------------
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-- \| Γ ⊢ w λx. e : Sτ → τ', S
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EAbs name e -> do
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fr <- fresh
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withBinding name (Forall [] fr) $ do
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(s1, t', e') <- algoW e
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let varType = apply s1 fr
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let newArr = TArr varType t'
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return (s1, newArr, T.EAbs newArr (name, varType) e')
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-- \| Γ ⊢ e₀ : τ₀, S₀ S₀Γ ⊢ e₁ : τ₁, S₁
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-- \| s₂ = mgu(s₁τ₀, Int) s₃ = mgu(s₂τ₁, Int)
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-- \| ------------------------------------------
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-- \| Γ ⊢ e₀ + e₁ : Int, S₃S₂S₁S₀
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-- This might be wrong
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EAdd e0 e1 -> do
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(s1, t0, e0') <- algoW e0
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applySt s1 $ do
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(s2, t1, e1') <- algoW e1
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-- applySt s2 $ do
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s3 <- unify (apply s2 t0) (TMono "Int")
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s4 <- unify (apply s3 t1) (TMono "Int")
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return
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( s4 `compose` s3 `compose` s2 `compose` s1
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, TMono "Int"
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, T.EAdd (TMono "Int") e0' e1'
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)
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-- \| Γ ⊢ e₀ : τ₀, S₀ S₀Γ ⊢ e₁ : τ₁, S1
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-- \| τ' = newvar S₂ = mgu(S₁τ₀, τ₁ → τ')
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-- \| --------------------------------------
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-- \| Γ ⊢ e₀ e₁ : S₂τ', S₂S₁S₀
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EApp e0 e1 -> do
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fr <- fresh
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(s0, t0, e0') <- algoW e0
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applySt s0 $ do
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(s1, t1, e1') <- algoW e1
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-- applySt s1 $ do
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s2 <- unify (apply s1 t0) (TArr t1 fr)
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let t = apply s2 fr
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return (s2 `compose` s1 `compose` s0, t, T.EApp t e0' e1')
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-- \| Γ ⊢ e₀ : τ, S₀ S₀Γ, x : S̅₀Γ̅(τ) ⊢ e₁ : τ', S₁
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-- \| ----------------------------------------------
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-- \| Γ ⊢ let x = e₀ in e₁ : τ', S₁S₀
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-- The bar over S₀ and Γ means "generalize"
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ELet name e0 e1 -> do
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(s1, t1, e0') <- algoW e0
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env <- asks vars
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let t' = generalize (apply s1 env) t1
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withBinding name t' $ do
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(s2, t2, e1') <- algoW e1
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return (s2 `compose` s1, t2, T.ELet (T.Bind (name, t2) e0') e1')
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ECase caseExpr injs -> do
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(_, t0, e0') <- algoW caseExpr
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(injs', ts) <- mapAndUnzipM (checkInj t0) injs
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case ts of
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[] -> throwError "Case expression missing any matches"
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ts -> do
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unified <- zipWithM unify ts (tail ts)
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let unified' = foldl' compose mempty unified
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let typ = apply unified' (head ts)
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return (unified', typ, T.ECase typ e0' injs')
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-- | Unify two types producing a new substitution
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unify :: Type -> Type -> Infer Subst
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unify t0 t1 = do
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case (t0, t1) of
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(TArr a b, TArr c d) -> do
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s1 <- unify a c
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s2 <- unify (apply s1 b) (apply s1 d)
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return $ s1 `compose` s2
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(TPol a, b) -> occurs a b
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(a, TPol b) -> occurs b a
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(TMono a, TMono b) ->
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if a == b then return M.empty else throwError "Types do not unify"
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-- \| TODO: Figure out a cleaner way to express the same thing
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(TConstr (Constr name t), TConstr (Constr name' t')) ->
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if name == name' && length t == length t'
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then do
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xs <- zipWithM unify t t'
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return $ foldr compose nullSubst xs
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else
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throwError $
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unwords
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[ "Type constructor:"
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, printTree name
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, "(" ++ printTree t ++ ")"
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, "does not match with:"
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, printTree name'
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, "(" ++ printTree t' ++ ")"
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]
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(a, b) ->
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throwError . unwords $
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[ "Type:"
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, printTree a
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, "can't be unified with:"
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, printTree b
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]
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{- | Check if a type is contained in another type.
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I.E. { a = a -> b } is an unsolvable constraint since there is no substitution
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such that these are equal
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-}
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occurs :: Ident -> Type -> Infer Subst
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occurs _ (TPol _) = return nullSubst
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occurs i t =
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if S.member i (free t)
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then
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throwError $
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unwords
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[ "Occurs check failed, can't unify"
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, printTree (TPol i)
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, "with"
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, printTree t
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]
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else return $ M.singleton i t
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-- | Generalize a type over all free variables in the substitution set
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generalize :: Map Ident Poly -> Type -> Poly
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generalize env t = Forall (S.toList $ free t S.\\ free env) t
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{- | Instantiate a polymorphic type. The free type variables are substituted
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with fresh ones.
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-}
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inst :: Poly -> Infer Type
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inst (Forall xs t) = do
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xs' <- mapM (const fresh) xs
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let s = M.fromList $ zip xs xs'
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return $ apply s t
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-- | Compose two substitution sets
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compose :: Subst -> Subst -> Subst
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compose m1 m2 = M.map (apply m1) m2 `M.union` m1
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-- | A class representing free variables functions
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class FreeVars t where
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-- | Get all free variables from t
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free :: t -> Set Ident
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-- | Apply a substitution to t
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apply :: Subst -> t -> t
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instance FreeVars Type where
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free :: Type -> Set Ident
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free (TPol a) = S.singleton a
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free (TMono _) = mempty
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free (TArr a b) = free a `S.union` free b
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-- \| Not guaranteed to be correct
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free (TConstr (Constr _ a)) =
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foldl' (\acc x -> free x `S.union` acc) S.empty a
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apply :: Subst -> Type -> Type
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apply sub t = do
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case t of
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TMono a -> TMono a
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TPol a -> case M.lookup a sub of
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Nothing -> TPol a
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Just t -> t
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TArr a b -> TArr (apply sub a) (apply sub b)
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TConstr (Constr name a) -> TConstr (Constr name (map (apply sub) a))
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instance FreeVars Poly where
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free :: Poly -> Set Ident
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free (Forall xs t) = free t S.\\ S.fromList xs
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apply :: Subst -> Poly -> Poly
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apply s (Forall xs t) = Forall xs (apply (foldr M.delete s xs) t)
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instance FreeVars (Map Ident Poly) where
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free :: Map Ident Poly -> Set Ident
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free m = foldl' S.union S.empty (map free $ M.elems m)
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apply :: Subst -> Map Ident Poly -> Map Ident Poly
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apply s = M.map (apply s)
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-- | Apply substitutions to the environment.
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applySt :: Subst -> Infer a -> Infer a
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applySt s = local (\st -> st{vars = apply s (vars st)})
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-- | Represents the empty substition set
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nullSubst :: Subst
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nullSubst = M.empty
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-- | Generate a new fresh variable and increment the state counter
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fresh :: Infer Type
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fresh = do
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n <- gets count
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modify (\st -> st{count = n + 1})
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return . TPol . Ident $ show n
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-- | Run the monadic action with an additional binding
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withBinding :: (Monad m, MonadReader Ctx m) => Ident -> Poly -> m a -> m a
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withBinding i p = local (\st -> st{vars = M.insert i p (vars st)})
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-- | Insert a function signature into the environment
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insertSig :: Ident -> Type -> Infer ()
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insertSig i t = modify (\st -> st{sigs = M.insert i t (sigs st)})
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-- | Insert a constructor with its data type
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insertConstr :: Ident -> Type -> Infer ()
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insertConstr i t =
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modify (\st -> st{constructors = M.insert i t (constructors st)})
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-------- PATTERN MATCHING ---------
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-- "case expr of", the type of 'expr' is caseType
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checkInj :: Type -> Inj -> Infer (T.Inj, Type)
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checkInj caseType (Inj it expr) = do
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(args, t') <- initType caseType it
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subst <- unify caseType t'
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trace ("SUBST: " ++ show subst) return ()
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applySt subst $ do
|
||||
(_, t, e') <- local (\st -> st { vars = args `M.union` vars st }) (algoW expr)
|
||||
return (T.Inj (it, t') e', t)
|
||||
|
||||
initType :: Type -> Init -> Infer (Map Ident Poly, Type)
|
||||
initType expected = \case
|
||||
InitLit lit -> do
|
||||
trace (show "EXPECTED: " ++ show expected ++ "\nreturnType: " ++ show (litType lit)) return ()
|
||||
if litType lit `isMoreSpecificOrEq` expected
|
||||
then return (mempty, litType lit)
|
||||
else
|
||||
throwError $
|
||||
unwords
|
||||
[ "Inferred type"
|
||||
, printTree $ litType lit
|
||||
, "does not match expected type:"
|
||||
, printTree expected
|
||||
]
|
||||
InitConstr c args -> do
|
||||
st <- gets constructors
|
||||
case M.lookup c st of
|
||||
Nothing ->
|
||||
throwError $
|
||||
unwords
|
||||
[ "Constructor:"
|
||||
, printTree c
|
||||
, "does not exist"
|
||||
]
|
||||
Just t -> do
|
||||
let flat = flattenType t
|
||||
let returnType = last flat
|
||||
case ( length (init flat) == length args
|
||||
, returnType `isMoreSpecificOrEq` expected
|
||||
) of
|
||||
(True, True) ->
|
||||
return
|
||||
( M.fromList $ zip args (map (Forall []) flat)
|
||||
, expected
|
||||
)
|
||||
(False, _) ->
|
||||
throwError $
|
||||
"Can't partially match on the constructor: "
|
||||
++ printTree c
|
||||
(_, False) ->
|
||||
throwError $
|
||||
unwords
|
||||
[ "Inferred type"
|
||||
, printTree returnType
|
||||
, "does not match expected type:"
|
||||
, printTree expected
|
||||
]
|
||||
InitCatch -> return (mempty, expected)
|
||||
|
||||
flattenType :: Type -> [Type]
|
||||
flattenType (TArr a b) = flattenType a ++ flattenType b
|
||||
flattenType a = [a]
|
||||
|
||||
litType :: Literal -> Type
|
||||
litType (LInt _) = TMono "Int"
|
||||
|
|
@ -15,6 +15,7 @@ import Data.Map (Map)
|
|||
import Data.Map qualified as Map
|
||||
import Data.Maybe (fromMaybe)
|
||||
import Data.Tuple.Extra (dupe)
|
||||
import Debug.Trace (trace)
|
||||
import Grammar.Abs
|
||||
|
||||
-- | Rename all variables and local binds
|
||||
|
|
@ -70,9 +71,9 @@ renameExp old_names = \case
|
|||
(new_names, e') <- renameExp old_names e
|
||||
pure (new_names, EAnn e' t)
|
||||
ECase e injs -> do
|
||||
(_, e') <- renameExp old_names e
|
||||
(new_names, injs') <- renameInjs old_names injs
|
||||
pure (new_names, ECase e' injs')
|
||||
(new_names, e') <- renameExp old_names e
|
||||
(new_names', injs') <- renameInjs new_names injs
|
||||
pure (new_names', ECase e' injs')
|
||||
|
||||
renameInjs :: Names -> [Inj] -> Rn (Names, [Inj])
|
||||
renameInjs ns xs = do
|
||||
|
|
@ -81,8 +82,16 @@ renameInjs ns xs = do
|
|||
|
||||
renameInj :: Names -> Inj -> Rn (Names, Inj)
|
||||
renameInj ns (Inj init e) = do
|
||||
(new_names, e') <- renameExp ns e
|
||||
return (new_names, Inj init e')
|
||||
(new_names, init') <- renameInit ns init
|
||||
(new_names', e') <- renameExp new_names e
|
||||
return (new_names', Inj init' e')
|
||||
|
||||
renameInit :: Names -> Init -> Rn (Names, Init)
|
||||
renameInit ns i = case i of
|
||||
InitConstr cs vars -> do
|
||||
(ns_new, vars') <- newNames ns vars
|
||||
return (ns_new, InitConstr cs vars')
|
||||
rest -> return (ns, rest)
|
||||
|
||||
-- | Create a new name and add it to name environment.
|
||||
newName :: Names -> Ident -> Rn (Names, Ident)
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue