Bug #13044: ruby unless bug with plural conditions

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 2.3.3p222 (2016-11-21 revision 56859) [x86_64-linux]
• Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN

[imran (Imran Ashraf)]

I am working on an app where I need to process various data-items based upon different ruby types. While setting up conditonal-checks, I discovered that "unless" fails to handle plural conditions.

Please consider the following example:

class ThingA end
class ThingB end
class ThingC end

# obj = ThingA.new
# obj = ThingB.new
obj = ThingC.new

# puts 'yes it is a ThingC' unless obj.is_a?(ThingA) && obj.is_a?(ThingB) # BUG

# puts 'yes it is a ThingC' if !obj.is_a?(ThingA) && !obj.is_a?(ThingB) # this works ok

# works ok with singular condition
unless obj.is_a?(ThingA)
  unless obj.is_a?(ThingB)
    puts 'yes it is a ThingC'
  end
end

Thanks.

Regards,
Imran

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)
• Status changed from Open to Rejected

unless a && b equals to if !(a && b).
See https://en.wikipedia.org/wiki/De_Morgan%27s_laws for more info.