def p_expr_id_substr(p):
    """ string : ID substr
    """
    entry = SYMBOL_TABLE.access_var(p[1], p.lineno(1), default_type=TYPE.string)
    p[0] = None
    if entry is None:
        return

    entry.accessed = True
    p[0] = make_strslice(p.lineno(1), entry, p[2][0], p[2][1])
string : ID substr