anchor.diff:    IgnoreValidator(this._errorReporter, this._reportedErrors, this._ignoreInfo,
         this._lineInfo) {
       var filePath = _errorReporter.source.fullName;
  -    for (var code in errorCodeValues) {
  -      if (!isIgnorable(filePath, code)) {
  -        unignorableNames.add(code.name.toLowerCase());
  -        unignorableNames.add(code.uniqueName.toLowerCase());
  -      }
  -    }
  +    _unignorableNames = _UnignorableNames.forFile(filePath);
     }
   
     /// Report any issues with ignore comments in the file being analyzed.
  
positive.code:   }
  
    static bool isIgnorable(String filePath, ErrorCode code) {
      if (code.isIgnorable) {
        return true;
      }
  
negative.code:     if ((code == CompileTimeErrorCode.IMPORT_INTERNAL_LIBRARY ||
              code == CompileTimeErrorCode.UNDEFINED_ANNOTATION ||
              code == ParserErrorCode.NATIVE_FUNCTION_BODY_IN_NON_SDK_CODE) &&
          isDart2jsTest) {
        // Special case the dart2js language tests. Some of these import
        // various internal libraries.
        return true;
  