anchor.diff:                let opt = option.decl; in
                 opt.apply (
                   if isNotDefined then
  -                  if opt ? default then opt.default
  -                  else throw "Not defined."
  +                  opt.default or (throw "Not defined.")
                   else opt.merge defs
                 )
               );
  
positive.code: 
  
    evalDefinitions = opt: values:
      if opt ? type && opt.type.delayOnGlobalEval then
        map (delayPropertiesWithIter opt.type.iter opt.name)
          (evalLocalProperties values)
      else
  
negative.code:               source = m.key;
              }) declarations;
  
            hasOptions = values != [];
            isOption = any lib.isOption values;
  
  