# File lib/bundler/definition.rb, line 344
    def validate_ruby!
      return unless ruby_version

      system_ruby_version = Bundler::SystemRubyVersion.new
      if diff = ruby_version.diff(system_ruby_version)
        problem, expected, actual = diff

        msg = case problem
        when :engine
          "Your Ruby engine is #{actual}, but your Gemfile specified #{expected}"
        when :version
          "Your Ruby version is #{actual}, but your Gemfile specified #{expected}"
        when :engine_version
          "Your #{system_ruby_version.engine} version is #{actual}, but your Gemfile specified #{ruby_version.engine} #{expected}"
        end

        raise RubyVersionMismatch, msg
      end
    end