anchor.diff:  
     # Merge definitions of a value of a given type.
     mergeDefinitions = loc: type: defs: rec {
  -    defsFinal =
  +    defsFinal' =
         let
           # Process mkMerge and mkIf properties.
           defs' = concatMap (m:
  
positive.code: 
       Note that "z" has the default priority 100.
    */
    filterOverrides = defs:
      let
        defaultPrio = 100;
        getPrio = def: if def.value._type or "" == "override" then def.value.priority else defaultPrio;
        highestPrio = foldl' (prio: def: min (getPrio def) prio) 9999 defs;
        strip = def: if def.value._type or "" == "override" then def // { value = def.value.content; } else def;
      in concatMap (def: if getPrio def == highestPrio then [(strip def)] else []) defs;
  
    /* Sort a list of properties.  The sort priority of a property is
       1000 by default, but can be overridden by wrapping the property
  
negative.code: 
      in opt //
        { value = builtins.addErrorContext "while evaluating the option `${showOption loc}':" value;
          inherit (res.defsFinal') highestPrio;
          definitions = map (def: def.value) res.defsFinal;
          files = map (def: def.file) res.defsFinal;
          inherit (res) isDefined;
  