[ruby-core:31336] Bug? Ruby 1.9.2-rc1: instance_eval can't handle a lambda (needs a proc)

I raised this on ruby-talk ( http://bit.ly/bruL6B ) and Caleb Clausen
advised it may be a bug.

Demonstrative code is saved in a gist ( http://bit.ly/bxgWQi ) and is
reproduced below.

class InstanceEval
  def initialize(code)
    @code = code
    @context = Object.new
  end

  def run
    code = @code
    result = @context.instance_eval(&code)
    "* run --> #{result.inspect}"
  end
end

p = proc { :p }
l = lambda { :l }

puts InstanceEval.new(p).run
puts InstanceEval.new(l).run

# The output in 1.8.7-p72 and in 1.9.1-p378:
#
# * run --> :p
# * run --> :l
#
# The output in 1.9.2-rc1:
#
# * run --> :p
# code.rb:15:... wrong number of arguments (1 for 0) (ArgumentError)
# from code.rb:10:in `instance_eval'

Caleb's comment:

    It seems like this could be a regression. The error message
    at the very least is a bug.