jruby-vs-refine.rb

module Refinements
  refine Object do
    def derp
      yield self
    end
  end
end

module A
  using Refinements

  def self.foo
    'test'.derp { |s| '(' + s + ')' }
  end
end

p A.foo
# jruby 9.1.6.0 (2.3.1) 2016-11-22 0150a76 OpenJDK Server VM 24.65-b04 on 1.7.0_65-b32 +jit [linux-i386]
#   NoMethodError: undefined method `derp' for "test":String
#        foo at tmp/ref.rb:13
#     <main> at tmp/ref.rb:17
#
# ruby 2.3.1
# => "(test)"