anchor.diff:      }
     }
   
  -  Set<String> get writtenFiles => _writtenFiles;
  -
     void _build(String filename, TemplateRenderer template, TemplateData data) {
       String fullName = path.join(out.path, filename);
   
  
positive.code:   String get faviconPath => _options.faviconPath;
    bool get useCategories => _options.useCategories;
    bool get prettyIndexJson => _options.prettyIndexJson;
    // Protect against bugs in canonicalization by tracking what files we
    // write.
    final Set<String> _writtenFiles = new Set();
  
    HtmlGeneratorInstance(this._options, this._templates, this.package, this.out,
        this._onFileCreated);
  
negative.code: 
      // If you see this assert, we're probably being called to build non-canonical
      // docs somehow.  Check data.self.isCanonical and callers for bugs.
      assert(!writtenFiles.contains(fullName));
      _writeFile(fullName, content);
      writtenFiles.add(fullName);
      if (data.self is ModelElement) documentedElements.add(data.self);
    }
  
  