leafify opt_plus
Inspired by 346aa557b31fe96760e505d30da26eb7a846bac9
Closes: https://github.com/ruby/ruby/pull/2321
leafify opt_plus
Inspired by 346aa557b31fe96760e505d30da26eb7a846bac9
Closes: https://github.com/ruby/ruby/pull/2321