Proc#bind implementation (active_support/core_ext/proc.rb)

Would it be a good idea to replace the implementation of Proc#bind in active_support/core_ext/proc.rb with:

class Proc #:nodoc:   def bind(object)     lambda { |*args| object.instance_exec *args, &self }   end end

I'm quite possibly overlooking something, but in my tests the above implementation respects arity restrictions under Ruby 1.9.2 better than the convoluted implementation in ActiveSupport.

In 1.8.7 the above implementation and the ActiveSupport implementation both return a bound Proc that can have different arity restrictions than what is passed in. Specifically, if you pass in a lambda, the above implementation will not raise an ArgumentException if you call the output with the wrong number of arguments. OTOH, the ActiveSupport version will raise an ArgumentException if you call the output with the wrong number of arguments even if you pass in a Proc created with Proc.new (where the actual number of arguments shouldn't matter).

What am I overlooking?