Small improvements, some errors here and there

[cc1516.git] / sem.icl

diff --git a/sem.icl b/sem.icl
index 24943fe..7f7cdf4 100644 (file)
--- a/sem.icl
+++ b/sem.icl
@@ -29,6 +29,7 @@ import AST
 
 :: Scheme = Forall [TVar] Type
 :: Gamma :== 'Map'.Map String Scheme //map from Variables! to types
+:: Typing a :== StateT (Gamma, [TVar]) (Either SemError) a
 :: Substitution :== 'Map'.Map TVar Type
 :: Constraints :== [(Type, Type)]
 :: SemError
@@ -48,12 +49,14 @@ instance zero Gamma where
 variableStream :: [TVar]
 variableStream = map toString [1..]
 
-sem :: AST -> Either [SemError] Constraints
+sem :: AST -> Either [SemError] AST
+//sem a = pure a
 sem (AST fd) = case foldM (const $ hasNoDups fd) () fd 
-               >>| foldM (const isNiceMain) () fd
-               >>| hasMain fd of
+                       >>| foldM (const isNiceMain) () fd
+                       >>| hasMain fd
+                    >>| evalStateT (type fd) (zero, variableStream) of
        Left e = Left [e]
-    _ = Right []
+    Right fds = Right (AST fds)
        //_ = case execRWST (constraints fd) zero variableStream of
        //      Left e = Left [e]
        //      Right (a, b) = Right b
@@ -144,12 +147,12 @@ occurs :: TVar a -> Bool | Typeable a
 occurs tvar a = elem tvar (ftv a)
 
 unify :: Type Type -> Either SemError Substitution
-unify t1=:(IdType tv) t2 = unify t2 t1
 unify t1 t2=:(IdType tv)    | t1 == (IdType tv) = Right zero
                             | occurs tv t1 = Left $ InfiniteTypeError zero t1
                             | otherwise = Right $ 'Map'.singleton tv t1
+unify t1=:(IdType tv) t2 = unify t2 t1
 unify (ta1->>ta2) (tb1->>tb2) = unify ta1 tb1 >>= \s1->
-                                unify tb1 tb2 >>= \s2->
+                                unify ta2 tb2 >>= \s2->
                                 Right $ compose s1 s2
 unify (TupleType (ta1,ta2)) (TupleType (tb1,tb2)) = unify ta1 tb1 >>= \s1->
                                                     unify ta2 tb2 >>= \s2->
@@ -161,8 +164,6 @@ unify t1 t2 | t1 == t2  = Right zero
 //// ------------------------
 //// Algorithm M, Inference and Solving
 //// ------------------------
-//The typing monad
-:: Typing a :== StateT (Gamma, [TVar]) (Either SemError) a
 gamma :: Typing Gamma
 gamma = gets fst
 putGamma :: Gamma -> Typing ()
@@ -307,7 +308,9 @@ instance infer [a] | infer a where
     infer []        = pure (zero, VoidType)
     infer [stmt:ss] = 
         infer stmt >>= \(s1, t1) ->
+        applySubst s1 >>|
         infer ss >>= \(s2, t2) ->
+        applySubst s2 >>|
         case t1 of
             VoidType = pure (compose s2 s1, t2)
             _ = case t2 of
@@ -321,46 +324,82 @@ class type a :: a -> Typing a
 
 instance type VarDecl where
     type (VarDecl p expected k e) = 
-        infer e >>= \(s, given) ->
-        applySubst s >>| 
+        infer e >>= \(s1, given) ->
+        applySubst s1 >>| 
         case expected of
             Nothing = pure zero
             Just expected_ = lift (unify expected_ given)
-        >>|
-        generalize given >>= \t ->
+        >>= \s2->
+        applySubst s2 >>|
+        let vtype = subst (compose s2 s1) given in
+        generalize vtype >>= \t ->
         changeGamma (extend k t) >>| 
-        pure (VarDecl p (Just given) k e)
+        pure (VarDecl p (Just vtype) k e)
 
 instance type FunDecl where
     type (FunDecl p f args expected vds stmts) = 
+        introduce f >>|
+        mapM introduce args >>= \argTs->
         type vds >>= \tVds->
-        infer stmts >>= \(s, given)->
-        applySubst s >>|
+        infer stmts >>= \(s1, result)->
+        let given = foldr (->>) result argTs in 
+        applySubst s1 >>|
         (case expected of
             Nothing = pure zero
             Just expected_ = lift (unify expected_ given))
-        >>|
-        generalize given >>= \t->
+        >>= \s2 ->
+        let ftype = subst (compose s2 s1) given in
+        generalize ftype >>= \t->
         changeGamma (extend f t) >>| 
-        pure (FunDecl p f args (Just given) tVds stmts)
+        pure (FunDecl p f args (Just ftype) tVds stmts)
+
+instance toString (Maybe a) | toString a where
+    toString Nothing = "Nothing"
+    toString (Just e) = concat ["Just ", toString e]
 
 instance type [a] | type a where
     type dcls = mapM type dcls
 
-
+introduce :: String -> Typing Type
+introduce k = 
+    fresh >>= \tv ->
+    changeGamma (extend k (Forall [] tv)) >>|
+    pure tv
 
 instance toString Scheme where
     toString (Forall x t) = 
-        concat ["Forall ": map ((+++) "\n") x] +++ toString t
+        concat ["Forall ": intersperse "," x] +++ concat [". ", toString t];
 
 instance toString Gamma where
     toString mp = 
         concat [concat [k, ": ", toString v, "\n"]\\(k, v)<-'Map'.toList mp]
 
+instance toString Substitution where
+    toString subs = 
+        concat [concat [k, ": ", toString t, "\n"]\\(k, t)<-'Map'.toList subs]
+
 instance toString SemError where
     toString (SanityError p e) = concat [toString p, 
         "SemError: SanityError: ", e]
-    toString se = "SemError: "
+    toString (ParseError p s) = concat [toString p, 
+        "ParseError: ", s]
+    toString (UnifyError p t1 t2) = concat [toString p, 
+        "Can not unify types, expected|given:\n", toString t1,
+        "\n", toString t2]
+    toString (InfiniteTypeError p t) = concat [toString p, 
+        "Infinite type: ", toString t]
+    toString (FieldSelectorError p t fs) = concat [toString p,
+        "Can not run fieldselector '", toString fs, "' on type: ",
+        toString t]
+    toString (OperatorError p op t) = concat [toString p,
+        "Operator error, operator '", toString op, "' can not be",
+        "used on type: ", toString t]
+    toString (UndeclaredVariableError p k) = concat [toString p,
+        "Undeclared identifier: ", k]
+    toString (ArgumentMisMatchError p str) = concat [toString p,
+        "Argument mismatch: ", str]
+    toString (Error e) = concat ["Unknown error during semantical",
+        "analysis: ", e]
 
 instance MonadTrans (StateT (Gamma, [TVar])) where
     liftT m = StateT \s-> m >>= \a-> return (a, s)