Gem.default_dir

# File tmp/rubies/ruby-3.0.5/lib/rubygems/defaults.rb, line 36
def self.default_dir
  path = if defined? RUBY_FRAMEWORK_VERSION
           [
             File.dirname(RbConfig::CONFIG['sitedir']),
             'Gems',
             RbConfig::CONFIG['ruby_version'],
           ]
         else
           [
             RbConfig::CONFIG['rubylibprefix'],
             'gems',
             RbConfig::CONFIG['ruby_version'],
           ]
         end

  @default_dir ||= File.join(*path)
end