class HasTokens a where
    firstTok :: a -> TT

instance HasTokens (Statement TT) where
    firstTok (FunDecl x _ _ _) = x
    firstTok (VarDecl x _ _) = x
    firstTok (Return x _ _) = x
    firstTok (While x _ _) = x
    firstTok (DoWhile x _ _ _ _) = x
    firstTok (For x _ _ _ _ _) = x
    firstTok (If x _ _ _) = x
    firstTok (Else x _) = x
    firstTok (With x _ _) = x
    firstTok (Comm x) = x
    firstTok (Expr x _) = firstTok x

instance HasTokens (Parameters TT) where
    firstTok (Parameters x _ _) = x
    firstTok (ParErr x) = x