With the new Ruby 3.2.0 now available as opt-in and new Standard bundled RubyGems added to Ruby 3.1.3, a particular RubyGems package collision scenario has been created:

• dev-ruby/debug was added as a new bundled RubyGem dependency of Ruby 3.1.3
• A dependency of dev-ruby/debug is dev-ruby/irb-1.6.2 or greater
• Ruby 3.2.0 has dev-ruby/irb-1.6.2 included as a RubyGem (Ruby 3.1.3 did not)
• If you have Ruby 3.2 RUBY_TARGET ruby31 a and ruby32 enabled, you will have dev-ruby/irb-1.6.2 installed as a dependency of Ruby 3.1.3, but an emerge -avuUDN @world will fail on dev-ruby/irb-1.6.2
• This is because Ruby 3.2.0 has irb 1.6.2 built in, and attempting to install a separate irb RubyGem with dev-ruby/irb-1.6.2 creates a package collision scenario that cannot proceed.

This should some how be cleanly handled before dev-lang/ruby-3.2.0 is unmasked in Funtoo next and set to the default RUBY_TARGET.