class I18n::Locale::Fallbacks

def compute(tags, include_defaults = true, exclude = [])
  result = Array(tags).flat_map do |tag|
    tags = I18n::Locale::Tag.tag(tag).self_and_parents.map! { |t| t.to_sym } - exclude
    tags.each { |_tag| tags += compute(@map[_tag], false, exclude + tags) if @map[_tag] }
    tags
  end
  result.push(*defaults) if include_defaults
  result.uniq!
  result.compact!
  result
end