From: John Firebaugh <john.firebaugh@...>
Date: 2012-03-16T12:42:14+09:00
Subject: [ruby-core:43323] [ruby-trunk - Bug #6151] ArgumentError of lambda shows wrong location


Issue #6151 has been updated by John Firebaugh.


The reason it raises an error is that instance_eval yields one argument (the receiver), and lambdas are strict about arity -- see #2476.
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Bug #6151: ArgumentError of lambda shows wrong location
https://bugs.ruby-lang.org/issues/6151#change-24627

Author: Thomas Sawyer
Status: Closed
Priority: Normal
Assignee: 
Category: core
Target version: 2.0.0
ruby -v: ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-linux]


=begin

Perhaps there is a reason, but it sure seems like a bug to me. Given this simple class:

      #
      class BlockParser < BasicObject
        def initialize(data={}, &block)
          @data = data
          instance_eval(&block)
        end

        def method_missing(name, *args, &block)
          if block
            @data[name] = {}
            BlockParser.new(@data[name], &block)
          else
            case args.size
            when 0
              @data[name]
            when 1
              @data[name] = args.first
            else
              @data[name] = args
            end
          end
        end
      end

Then we can do:

      data = {}
      BlockParser.new(data) do
        name 'Tommy'
      end
      data #=> {:name=>'Tommy'}

But,

      data = {}
      blk  = lambda do
        name 'Tommy'
      end
      BlockParser.new(data, &blk)
      ArgumentError: wrong number of arguments (1 for 0)
      	from (irb):44:in `block in irb_binding'
      	from (irb):16:in `instance_eval'
      	from (irb):16:in `initialize'
      	from (irb):46:in `new'
      	from (irb):46
      	from /home/trans/.rbfu/rubies/1.9.3-p0/bin/irb:12:in `<main>'

If I use (({Proc.new})) instead of (({lambda})) it works. But since I am using (({#instance_eval})) to evaluate the Proc, that shouldn't matter.

Note the reported line number of the error corresponds to (({name 'Tommy'})).
=end



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