Gem::BasicSpecification#source_paths

# File tmp/rubies/ruby-3.0.5/lib/rubygems/basic_specification.rb, line 256
def source_paths
  paths = raw_require_paths.dup

  if have_extensions?
    ext_dirs = extensions.map do |extension|
      extension.split(File::SEPARATOR, 2).first
    end.uniq

    paths.concat ext_dirs
  end

  paths.uniq
end