UnboundMethod#parameters for an assignment method wrongly returns blank array #2816
Description
➜ rspec-mocks git:(master) ✗ chruby 2.1
➜ rspec-mocks git:(master) ✗ ruby -v -e 'puts Class.new { attr_accessor :foo }.instance_method(:foo=).parameters.inspect'
ruby 2.1.5p273 (2014-11-13 revision 48405) [x86_64-darwin12.0]
[[:req]]
➜ rspec-mocks git:(master) ✗ chruby jruby
➜ rspec-mocks git:(master) ✗ ruby -v -e 'puts Class.new { attr_accessor :foo }.instance_method(:foo=).parameters.inspect'
jruby 1.7.8 (1.9.3p392) 2013-11-14 0ce429e on Java HotSpot(TM) 64-Bit Server VM 1.6.0_65-b14-462-11M4609 [darwin-x86_64]
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rspec-mocks relies upon parameters for verifying doubles to ensure the method signature of the real object supports the provided arguments, and it's not working properly for assignment methods on JRuby due to this bug (see rspec/rspec-mocks#919).