undefined method `local_names' in Method#parameters

[michaeldv]

Hi there,

Discovered this while trying to make awesome_print gem work with rbx-head:

$ irb -f
irb> m = [].method(:length)
=> #<Method: Array#length (defined in Array)>
irb> m.parameters
NoMethodError: undefined method `local_names' on an instance of Rubinius::AccessVariable.
   from Kernel(Rubinius::AccessVariable)#local_names (method_missing) at kernel/delta/kernel.rb:79
   from Method#parameters at kernel/common/method.rb:119

It seems that the following fixes the issue (added line 119 in kernel/common/method.rb):

118: def parameters
119:   return [] if Rubinius::AccessVariable === @executable
120:   @executable.local_names.each_with_index.map do |name, i|

However here's more complicated case that involves Rubinius::NativeMethod:

$ irb -f
irb> require "bigdecimal"
=> true
irb> Class Hi
irb> end
=> nil
irb> m = Hi.method(:BigDecimal)
=> #<Method: Class#BigDecimal (defined in Kernel at vm/capi/module.cpp:0)>
irb> m.parameters
NoMethodError: undefined method `local_names' on an instance of Rubinius::NativeMethod.
   from Kernel(Rubinius::NativeMethod)#local_names (method_missing) at kernel/delta/kernel.rb:79
   from Method#parameters at kernel/common/method.rb:119

In theory BigDecimal should show its parameters just like any other method, so returning [] doesn't seem right in this case.

I think the same issue might affect UnboundMethod#parameters. Let me know if you'd like me to dig deeper ;-)

Michael