left-recursion ;-(

gistfile1.hs

var :: Parser Var
var = buildVar <$> namePart <*> funcalls <*> selectors

  where namePart :: Parser (Either Name Exp)
        namePart = (Right <$> between (spChar '(') (spChar ')') exp)
               <|> (Left  <$> name)

        funcalls :: Parser [(Maybe Name, FunArg)]
        funcalls = many argPart

        selectors :: Parser [(Either Exp Name)]
        selectors = many $
                (Left  <$> between (spChar '[') (spChar ']') exp)
            <|> (Right <$> (spChar '.' >> name))

        methodName :: Parser Name
        methodName = spChar ':' >> name

        argPart :: Parser (Maybe Name, FunArg)
        argPart = (,) <$> optionMaybe methodName <*> funArg

        buildVar :: Either Name Exp -> [(Maybe Name, FunArg)] -> [(Either Exp Name)] -> Var
        buildVar (Left name) ((Just methodName, args):rest) selectors = 
            buildVar' (PEFunCall (MethodCall (PEVar (Name name)) methodName args)) rest selectors
        buildVar (Left name) ((Nothing, args):rest) selectors =
            buildVar' (PEFunCall (NormalFunCall (PEVar (Name name)) args)) rest selectors

        buildVar (Right exp) ((Just methodName, args):rest) selectors =
            buildVar' (PEFunCall (MethodCall (Paren exp) methodName args)) rest selectors
        buildVar (Right exp) ((Nothing, args):rest) selectors =
            buildVar' (PEFunCall (NormalFunCall (Paren exp) args)) rest selectors

        buildVar (Left name) [] ((Left exp):rest) =
            buildVar'' (Select (PEVar (Name name)) exp) rest
        buildVar (Left name) [] ((Right name'):rest) =
            buildVar'' (SelectName (PEVar (Name name)) name') rest

        buildVar (Right exp) [] ((Left exp'):rest) =
            buildVar'' (Select (Paren exp) exp') rest
        buildVar (Right exp) [] ((Right name):rest) =
            buildVar'' (SelectName (Paren exp) name) rest

        buildVar (Left name) [] [] = Name name
        buildVar (Right _) [] [] = undefined -- this is an error

        buildVar' :: PrefixExp -> [(Maybe Name, FunArg)] -> [(Either Exp Name)] -> Var
        buildVar' pe ((Just name, args):rest) selectors =
            buildVar' (PEFunCall (MethodCall pe name args)) rest selectors
        buildVar' pe ((Nothing, args):rest) selectors =
            buildVar' (PEFunCall (NormalFunCall pe args)) rest selectors
        buildVar' pe [] ((Left exp):rest) =
            buildVar'' (Select pe exp) rest
        buildVar' pe [] ((Right name):rest) =
            buildVar'' (SelectName pe name) rest
        buildVar' _ [] [] = undefined -- error

        buildVar'' :: Var -> [(Either Exp Name)] -> Var
        buildVar'' var ((Left exp):rest) =
            buildVar'' (Select (PEVar var) exp) rest
        buildVar'' var ((Right name):rest) =
            buildVar'' (SelectName (PEVar var) name) rest
        buildVar'' var [] = var