RubyVM logic in forwardable backported to 2.3, not removed
Logic was added to forwardable.rb in at least one commit, and revised in others:
On trunk, this logic was eventually replaced with code that works on Ruby impls other than MRI:
I request that RubyVM not ever be used in stdlib unless guarded with a RUBY_ENGINE check plus fallback code. It is not possible for any implementation other than MRI to support RubyVM::InstructionSequence and whenever it is used in tests or stdlib we have to patch around it.
Please backport the remaining changes to forwardable to the ruby-2_3 branch for release, so we can return to using the stock forwardable.rb in JRuby.