From: funny.falcon@...
Date: 2015-06-18T19:11:57+00:00
Subject: [ruby-core:69664] [Ruby trunk - Bug #11283] Block assigned	implicitly

Issue #11283 has been updated by Yura Sokolov.


This is "hidden feature", not the bug: `Proc.new` can consume unnamed block passed to method.
It makes possible following code:

````ruby
    def do_now_or_later
      if can_do_now?
        yield
      else
        do_it_later Proc.new
      end
    end
    do_now_or_later { puts 'hi' }
````

In your case block is passed to implicit `Proc.new` in the implementation of `define_method`.

I agree, that it is a bit weird feature.

----------------------------------------
Bug #11283: Block assigned implicitly
https://bugs.ruby-lang.org/issues/11283#change-53025

* Author: Andrew Kozin
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: 1.9.3, 2.0, 2.1, 2.2, ruby-head
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
That is how it works:

    module Test
      def self.build(&block)
        klass = Class.new(Object)
        klass.__send__(:define_method, :foo)
        klass.__send__(:define_method, :bar)
        klass
      end
    end

    Tested = Test.build { :foo }
    # warning: tried to create Proc object without a block
    # => Tested
    Tested.new.foo
    # => :foo
    Tested.new.bar
    # => :foo

The block is assigned to all calls to `:define_method` via `Object#__send__` implicitly, while it wasn't asked to.

The behaviour is tested under MRI 1.9.3, 2.0, 2.1, 2.2, ruby-head. It doesn't occur under rbx-2 and jruby (1.7, 9.0.0.0).

For the context look at this thread https://github.com/mbj/mutant/issues/356



-- 
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