In the event of the termination or partial termination of the Retirement System or in the event of complete discontinuance of contributions under the Retirement System, the rights of all affected members to benefits accrued to the date of such termination, partial termination, or discontinuance, to the extent funded as of such date, or the amounts credited to the members’ accounts, shall be nonforfeitable and fully vested. (1987; c. 177, s. 1(a), (b).)