[ruby-core:74070] [Ruby trunk Feature#12113] Global method inside Delegator causes NameError

Issue #12113 has been updated by Nobuyoshi Nakada.


Correction: the infinite recursion was a bug in the patch, and fixed the branch.

The trick of `Kernel` for [Bug #9155] is for the case a global method is called *before* the target object is set.
It is for the backward compatibility and convenience, we may be better to warn to use `::` and remove it in the future.

----------------------------------------
Feature #12113: Global method inside Delegator causes NameError
https://bugs.ruby-lang.org/issues/12113#change-57221

* Author: Oleg Antonyan
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------
~~~ruby
def some_func
  puts '12'
end

class Klass < Delegator
  def initialize(obj)
    @obj = obj
  end

  def __getobj__
    @obj
  end

  def func
    some_func #=> /home/oleg/.rbenv/versions/2.3.0/lib64/ruby/2.3.0/delegate.rb:85:in `instance_method': undefined method `some_func' for module `Kernel' (NameError)
  end
end

Klass.new(0).func
~~~
Delegator uses Kernel.instance_method (https://github.com/ruby/ruby/blob/trunk/lib/delegate.rb#L85) but:

~~~ruby
::Kernel.respond_to?(:some_func, true) #=> true
::Kernel.instance_method(:some_func)   #=> `instance_method': undefined method `some_func' for module `Kernel' (NameError)
::Kernel.method(:some_func)            #=> #<Method: Module(Object)#some_func>
~~~

I think there should be `Kernel.method` instead of `instance_method` (in Delegator). Otherwise you get `respond_to?` == `true`, but cannot use this method and get an error.



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