According to http://redmine.ruby-lang.org/issues/1183 , Ruby 1.9's {foo: 42}
apparently was back-ported to Ruby 1.8. But I tried running ruby-1.8.7-head using RVM, and I got the standard syntax error:
Andrew-Grimms-MacBook-Pro:ruby agrimm$ rvm use ruby-1.8.7-head
Using /Users/agrimm/.rvm/gems/ruby-1.8.7-head
Andrew-Grimms-MacBook-Pro:ruby agrimm$ irb
ruby-1.8.7-head :001 > {a: "foo"}
SyntaxError: compile error
(irb):1: odd number list for Hash
{a: "foo"}
^
(irb):1: syntax error, unexpected ':', expecting '}'
{a: "foo"}
^
(irb):1: syntax error, unexpected '}', expecting $end
from (irb):1
Has the change been reverted, or are not all changes to the source code reflected in ruby-1.8.7-head?