brew/Library/Homebrew/fetch.rb

module Homebrew
  module Fetch
    module_function

    def fetch_bottle?(f)
      return true if ARGV.force_bottle? && f.bottle
      return false unless f.bottle && f.pour_bottle?
      return false if ARGV.build_formula_from_source?(f)
      return false unless f.bottle.compatible_cellar?

      true
    end
  end
end