AR Association Proxy prevents calling methods defined using method_missing on the target of the association

From the commit:

Don't raise a NoMethodError if the target does not respond_to? method. This excludes methods on target that are implemented using method_missing. And if the method really doesn't exist, target.send(method, args) will raise a NoMethodError itself...so let it do that.

Description:

If I have a model like this:

class User < ActiveRecord::Base
# Provide is_admin?, is_guest? account type discovery methods def method_missing(method_id, *arguments)

if match = /^is_(\w+)\?$/.match(method_id.to_s)
  self.account_type == match[1]
else
  super
end

end end

class Activity < ActiveRecord::Base
belongs_to :user end

I can't do Activity.first.user.is_guest? because it raises a NoMethodError. The problem is that the Association Proxy only allows calling methods on the target that respond_to?(method). It doesn't need to do this check, because if the method really doesn't exist, the call to target.send(method, args) will raise NoMethodError itself, so nothing is gained by doing that check in the proxy.