From: Jeremy Evans <merch-redmine@...>
Date: 2011-07-06T00:34:31+09:00
Subject: [ruby-core:37801] [Ruby 1.9 - Feature #3768] Constant Lookup doesn't work in a subclass of BasicObject


Issue #3768 has been updated by Jeremy Evans.


Thomas, your example works on 1.9.2p180:

$ ruby -v
ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-openbsd4.9]
$ cat > q.rb
  class R
  end

  class Q < BasicObject
    def r; R.new; end
  end
$ irb
irb(main):001:0> module M; eval(File.read('q.rb')); end
=> nil
irb(main):002:0> M::Q.new.r
=> #<M::R:0x00000208a42590>

It doesn't work if you change R.new to ::R.new, but that's to be expected (it would be the same if Q descended from Object).

It even works if R and Q are defined in separate files:

$ cat > r.rb
  class R
  end
$ cat > q.rb
  class Q < BasicObject
    def r; R.new; end
  end
$ irb
irb(main):001:0> module M; eval(File.read('r.rb')); end
=> nil
irb(main):002:0> module M; eval(File.read('q.rb')); end
=> nil
irb(main):003:0> M::Q.new.r
=> #<M::R:0x0000020b76cbb0>

The behavior is still the same on "ruby 1.9.3dev (2011-02-28 trunk 30975) [x86_64-openbsd4.9]", so if it no longer works, it must have changed in the last few months.

I agree that constant lookup and method lookup are not the same thing, and should not necessarily be treated the same way.  However, I think the purpose of BasicObject is, to the extent possible, remove the default behavior that most objects have in order to allow the programmer to define their own behavior.  Therefore, I think allowing the programmer control over constant lookup in BasicObject subclasses makes sense.
----------------------------------------
Feature #3768: Constant Lookup doesn't work in a subclass of BasicObject
http://redmine.ruby-lang.org/issues/3768

Author: Thomas Sawyer
Status: Rejected
Priority: Normal
Assignee: Yukihiro Matsumoto
Category: lib
Target version: 


=begin
 ruby-1.9.2-p0 > module M
 ruby-1.9.2-p0 ?>  end
  => nil
 ruby-1.9.2-p0 > class X < BasicObject
 ruby-1.9.2-p0 ?>    include M
 ruby-1.9.2-p0 ?>  end
 NameError: uninitialized constant X::M
         from (irb):4:in `<class:X>'
         from (irb):3
         from /home/trans/.rvm/rubies/ruby-1.9.2-p0/bin/irb:17:in `<main>'
=end



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