anchor.diff:  
   rec {
   
  -  inherit (lib) isType;
  -  
  -
  -  isOption = isType "option";
  +  isOption = lib.isType "option";
     mkOption = attrs: attrs // {
       _type = "option";
       # name (this is the name of the attributem it is automatically generated by the traversal)
  
positive.code:               if all opt.check list then
                  opt.merge list
                else
                  throw "One of option ${name} values has a bad type.";
            }
          else opt;
  
  
negative.code:               if opt.check opt.default then
                  opt.default
                else
                  throw "The default value of the option `${name}' has a bad type.";
            }
          else opt;
  
  