require "requirement" class MaximumMacOSRequirement < Requirement fatal true def initialize(tags) @version = MacOS::Version.from_symbol(tags.first) super end satisfy(:build_env => false) { MacOS.version <= @version } def message <<-EOS.undent This formula either does not compile or function as expected on OS X versions newer than #{@version.pretty_name} due to an upstream incompatibility. EOS end end