ret : ident
        | LBRACKET RBRACKET
        | LBRACKET expr_list RBRACKET

def p_ret(p):
    """
    ret : ident
        | LBRACKET RBRACKET
        | LBRACKET expr_list RBRACKET
    """
    if len(p) == 2:
        p[0] = node.expr_list([p[1]])
    elif len(p) == 3:
        p[0] = node.expr_list([])
    elif len(p) == 4:
        assert isinstance(p[2], node.expr_list)
        p[0] = p[2]
    else:
        assert 0
    for ident in p[0]:
        ident.props = "F"