From: Markus <markus@...>
Date: 2005-05-24T05:04:26+09:00
Subject: Array.=== Bug, Rails Bug, or brain failure?

I've got some rails code that is failing in a very strange way.  It is
quite repeatable in situ, but I have yet to formulate a simple
explanation of when it fails.

Consider this code:

    case x
       when Array
          print "Array\n"
       else
          print "Bogus\n" if x.is_a? Array
       end

Should it ever print "Bogus\n"?  I wouldn't think so, but when x is  the
Array returned by main_record.sub_records (where main_record is linked
to sub_records by a "has_many :sub_record") it does.

The class of x is "Array" and (obviously) "x.is_a? Array" but "Array ===
x" returns false.  It works for hand made arrays, the Array returned by
"SubRecord.find_all_by_main_record(main_record.id)"--which should be
identical. 

I've only found one place in the whole codebase (in activerecord) where
=== is redefined, and then only for active records themselves, not for
the class, and certainly not for Class. In any case, it "redefines" it
as "other.is_a?(self)", which is what I'd expect class to do.

Adding:

class Array
    def self.===(other)
        other.is_a? self
        end
    end

right above the code in question fixes it.

Has anyone else seen this? Did the semantics change when I wasn't
looking?  Or is there a bug somewhere?  Or am I missing something subtly
obvious?

--MarkusQ