Gem::Specification#base_dir

# File tmp/rubies/ruby-4.0.0/lib/rubygems/specification.rb, line 1980
def base_dir
  return Gem.dir unless loaded_from
  @base_dir ||= if default_gem?
    File.dirname File.dirname File.dirname loaded_from
  else
    File.dirname File.dirname loaded_from
  end
end