+ >>= \t1-> typeExpr e2 >>= \t2-> pure $ TupleType (t1, t2)
+typeExpr (Op2Expr p e1 op e2)
+| isMember op [BiPlus, BiMinus, BiTimes, BiDivide, BiMod] =
+ typeOp2 e1 e2 op [IntType] IntType
+| isMember op [BiEquals, BiUnEqual] =
+ typeOp2 e1 e2 op [IntType, BoolType, CharType] BoolType
+| isMember op [BiLesser, BiGreater, BiLesserEq, BiGreaterEq] =
+ typeOp2 e1 e2 op [IntType, CharType] BoolType
+| isMember op [BiAnd, BiOr] =
+ typeOp2 e1 e2 op [BoolType] BoolType
+| op == BiCons = typeExpr e1 >>= \t1-> typeExpr e2
+ >>= \t2-> unify (ListType t1) t2
+typeExpr (EmptyListExpr p) = freshIdent >>= \frsh-> let t = IdType frsh in
+ putIdent frsh t >>| pure t
+typeExpr (FunExpr p (FunCall f es)) = typeFun f es
+typeExpr (VarExpr p (VarDef ident fs)) = gets (\(st, r)->'Map'.get ident st)
+ >>= \mt->case mt of
+ Nothing = liftT $ Left $ UndeclaredVariableError p ident
+ Just t = unify t fs
+
+typeOp2 :: Expr Expr Op2 [Type] Type -> Env Type
+typeOp2 e1 e2 op ts ret = typeExpr e1 >>= \t1-> typeExpr e2 >>= \t2->
+ unify t1 t2 >>= \t3->if (isMember t3 ts) (pure ret)
+ (liftT $ Left $ OperatorError (extrPos e1) op t3)
+
+buildFunctionType :: String [Expr] -> Env Type
+buildFunctionType frsh [] = let t = IdType frsh in putIdent frsh t >>| pure t
+buildFunctionType frsh [e:es] = (->>) <$> typeExpr e <*> buildFunctionType frsh es
+
+unifyApp :: Type [Expr] -> Env Type
+unifyApp t [] = pure t //whoop whoop, functions can return functions
+unifyApp (tf1 ->> tf2) [t1:ts] = unify tf1 t1 >>| unifyApp tf2 ts
+unifyApp t1 t2 = liftT $ Left $ UnifyError zero t1 (IdType "[expressions, FIXME]")
+
+typeFun :: String [Expr] -> Env Type
+typeFun f es = gets (\(st, r)->'Map'.get f st) >>= \mt-> case mt of
+ Nothing = freshIdent >>= \frsh-> buildFunctionType frsh es
+ >>= \ft-> putIdent f ft >>| (pure $ IdType frsh)
+ Just t = unifyApp t es
+
+resultType :: Type -> Type
+resultType (_ ->> t) = resultType t
+resultType t = t