anchor.diff:      final visitor = _Visitor(this);
       registry.addClassDeclaration(this, visitor);
       registry.addClassTypeAlias(this, visitor);
  +    registry.addCompilationUnit(this, visitor);
       registry.addConstructorDeclaration(this, visitor);
       registry.addEnumConstantDeclaration(this, visitor);
       registry.addEnumDeclaration(this, visitor);
  
positive.code:   @override
    void visitClassTypeAlias(ClassTypeAlias node) {
      checkComment(node.documentationComment);
    }
  
    @override
  
negative.code:   }
  
    @override
    void visitMethodDeclaration(MethodDeclaration node) {
      checkComment(node.documentationComment);
    }
  