From: Yuri Kozlov <kozlov.y@...>
Date: 2005-11-27T16:12:28+09:00
Subject: Re: warning: default `to_a' will be obsolete

and in the 1.9.0 it is already happens
irb(main):001:0> x = 1
=> 1
irb(main):002:0> x.to_a
NoMethodError: undefined method `to_a' for 1:Fixnum
        from (irb):2
irb(main):003:0>