anchor.diff:  
     Builder? lookup(String name, int charOffset, Uri fileUri,
         {bool isInstanceScope: true}) {
  -    recordUse(name, charOffset, fileUri);
  +    recordUse(name, charOffset);
       Builder? builder =
           lookupIn(name, charOffset, fileUri, _local, isInstanceScope);
       if (builder != null) return builder;
  
positive.code: 
    Builder? lookupSetter(String name, int charOffset, Uri fileUri,
        {bool isInstanceScope: true}) {
      recordUse(name, charOffset, fileUri);
      Builder? builder =
          lookupIn(name, charOffset, fileUri, _setters, isInstanceScope);
      if (builder != null) return builder;
  
negative.code:         isModifiable: true);
    }
  
    void recordUse(String name, int charOffset) {
      if (isModifiable) {
        usedNames ??= <String, int>{};
        // Don't use putIfAbsent to avoid the context allocation needed
  