From: Paul Brannan <pbrannan@...>
Date: 2002-05-18T05:50:56+09:00
Subject: Exceptions and <=>

I was playing with <=> recently, and I noticed that the following:

  class Foo
    def ==(other)
      raise "uh oh"
    end
  end
  p Foo.new == 42

prints (on Ruby 1.6 and 1.7):

  -:3:in `==': uh oh (RuntimeError)
          from -:6

However:

  class Foo
    include Comparable
    def <=>(other)
      raise "uh oh"
    end
  end
  p Foo.new == 42

prints:

  false

While this makes sense (if <=> raises an exception, then the two values
probably weren't equal), it is inconsistent.  If an exception gets
propogated in one case, it should be propogated in another case.  I
think it would be preferable for <=> to always propogate the exception,
since some exceptions (ArgumentError, NameError, etc.) often indicate
bugs, and catching them prevents unit tests from catching potential
problems.

Any thoughts?

Paul