anchor.diff:      catAttrs
       concatLists
       concatMap
  -    count
       elem
       filter
       findFirst
  
positive.code:                   unmatchedDefns = [];
                  }
                else
                  throw "The option `${showOption loc}' in `${firstOption._file}' is a prefix of options in `${firstNonOption._file}'."
            else
              mergeModules' loc decls defns) declsByName;
  
  
negative.code:           loc = prefix ++ [name];
            defns = defnsByName.${name} or [];
            defns' = defnsByName'.${name} or [];
            optionDecls = filter (m: isOption m.options) decls;
          in
            if length optionDecls == length decls then
              let opt = fixupOptionType loc (mergeOptionDecls loc decls);
              in {
                matchedOptions = evalOptionValue loc opt defns';
                unmatchedDefns = [];
              }
            else if optionDecls != [] then
                if (lib.head optionDecls).options.type.name == "submodule"
                then
                  let opt = fixupOptionType loc (mergeOptionDecls loc (map optionTreeToOption decls));
                  in {
  