anchor.diff:  import 'package:angular_compiler/v1/src/compiler/template_parser/recursive_template_visitor.dart';
   import 'package:angular_compiler/v1/src/compiler/view_compiler/view_compiler_utils.dart';
   import 'package:angular_compiler/v2/context.dart';
  +
  +const String optedOutValidator = 'If your project uses selector css styling '
  +    'heavily, or the templates contain external custom elements not supported by '
  +    'ACX, then this feature might not be a good fit for your project. To prevent '
  +    'compilation errors, please add your project to the disallow list in '
  +    'go/opted-out-missing-directive-validator';
   
   /// A validator to catch missing elements, direcitves, attributes, and outputs.
   ///
  
positive.code:         BuildError.forSourceSpan(
            ast.sourceSpan,
            'A selector in @skipSchemaValidationFor="'
            '${ast.skipSchemaValidationForSelector}" does not match this element',
          ),
        );
      }
  
negative.code:           "Can't find '<$elementName>'. Please check that the spelling "
            'is correct, and that the intended component is included in the '
            "host component's list of directives. "
            'See more details go/skipschemavalidationfor.\n$optedOutValidator',
          ),
        );
      }
  