In my application, I'm using the active_interaction gem and the following works in MRI 2.2.2, JRuby 1.7.20, JRuby 9.pre1: https://gist.github.com/egadstar/6b33d76d8b3fc44733dc

In 9K.pre2 and 9K.rc1, I get the following when running the gist:

NoMethodError: private method foobar=' called for #<Bar::Foo:0x2488b073> from org/jruby/RubyKernel.java:1821:inpublic_send'
from /Users/egadstar/.rvm/gems/jruby-9.0.0.0.rc1/gems/active_interaction-2.0.1/lib/active_interaction/base.rb:225:in block in populate_filters' from org/jruby/RubyHash.java:1342:ineach'
from /Users/egadstar/.rvm/gems/jruby-9.0.0.0.rc1/gems/active_interaction-2.0.1/lib/active_interaction/base.rb:223:in populate_filters' from /Users/egadstar/.rvm/gems/jruby-9.0.0.0.rc1/gems/active_interaction-2.0.1/lib/active_interaction/base.rb:215:inprocess_inputs'
from /Users/egadstar/.rvm/gems/jruby-9.0.0.0.rc1/gems/active_interaction-2.0.1/lib/active_interaction/base.rb:166:in initialize' from /Users/egadstar/.rvm/gems/jruby-9.0.0.0.rc1/gems/active_interaction-2.0.1/lib/active_interaction/concerns/runnable.rb:108:innew'
from /Users/egadstar/.rvm/gems/jruby-9.0.0.0.rc1/gems/active_interaction-2.0.1/lib/active_interaction/concerns/runnable.rb:122:in run' from (irb):2:in'
from org/jruby/RubyKernel.java:979:in eval' from org/jruby/RubyKernel.java:1292:inloop'
from org/jruby/RubyKernel.java:1099:in catch' from org/jruby/RubyKernel.java:1099:incatch'