IPAddr.new("0.0.0.0") == nil and nil == IPAddr.new("0.0.0.0") return different results.

This Pull Request fixes IPAddr.new("0.0.0.0") == nil so that it returns false, consistent with the behavior of IPAddr.new("0.0.0.0").nil?.

• Fix IPAddr.new("0.0.0.0") == nil and nil == IPAddr.new("0.0.0.0") return different results #75

Steps to reproduce

# IPv4
IPAddr.new("0.0.0.0") == nil
#=> true # expected false

nil == IPAddr.new('0.0.0.0')
#=> false

IPAddr.new("0.0.0.0").nil?
#=> false

# IPv6
IPAddr.new("::") == nil
#=> true # expected false

nil == IPAddr.new("::")
#=> false

IPAddr.new("::").nil?
#=> false

Expected behavior

IPAddr.new("0.0.0.0") == nil should return false, just like IPAddr.new("0.0.0.0").nil?.

Actual behavior

IPAddr.new("0.0.0.0") == nil return true.

System configuration

• IPAddr version: 1.2.8
• Ruby version: 4.0.1
  • ruby 4.0.1 (2026-01-13 revision e04267a14b) +PRISM [arm64-darwin25]

Additional Information

This issue was discovered while investigating the following report:

• Fix PostgreSQL Cidr#change?: NoMethodError: undefined method `prefix' for nil rails/rails#51758 (comment)