[ruby-core:27230] [Bug #2502] strange behavior of anonymous class inside a proc

Bug #2502: strange behavior of anonymous class inside a proc
http://redmine.ruby-lang.org/issues/show/2502

Author: caleb clausen
Status: Open, Priority: High
ruby -v: ruby 1.9.1p376 (2009-12-07 revision 26040 [x86_64-linux]

I have a problem in 1.9.1 when I run this code, extracted from a larger project:
  $VERBOSE=1

  class SubSeq 
    def initialize
      @first=11
      @first or fail
    end

    def subseq 
      @first or fail
    end    
  end

  class Indexed  
    def subseq 
      SubSeq.new
    end
  end

  Overlaid =proc do
    p self
    class<<self
      def subseq
        super.instance_eval(& Overlaid)
      end
    end
  end

  mid=Indexed.new
  mid.instance_eval(&Overlaid)
  mid.subseq
  p mid
  mid.subseq 

The output I get is like this:
#<Indexed:0x000000007a8930>
#<SubSeq:0x000000007a7e78 @first=11>
#<Indexed:0x000000007a8930>
subseq_first_nil.rb:10: warning: instance variable @first not initialized
subseq_first_nil.rb:10:in `subseq': unhandled exception
	from subseq_first_nil.rb:24:in `subseq'
	from subseq_first_nil.rb:33:in `<main>'

This code should run without raising an exception, and does in ruby 1.8. The exception is raised from within the last line, the second call to mid.subseq. Both mid.subseq calls should behave exactly the same. The first appears to do all the right things. But in the second, it goes all awry. They should both call first the anonymous class's #subseq, then (via the super) Indexed#subseq, which ultimately returns a SubSeq object, also decorated by the anonymous class. SubSeq#subseq itself should never be called, but somehow (given the top line of the exception traceback and the warning) it is. SubSeq's @first should never be nil, since it is initialized in the constructor and never changed, but somehow it is. 

This is the last remaining (serious) problem in porting redparse to 1.9. It causes redparse to incorrectly handle certain here documents which work fine when run in 1.8. I'd appreciate it very much of this problem can be fixed.

I've observed this in 1.9.1, but not 1.9.2.


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