anchor.diff:  /// other words, if this information (or any information it refers to) changes,
   /// static analysis and runtime behavior of the library are unaffected.
   const informative = null;
  +
  +Location _getLocationInProgram(Program program, String fileUri, int offset) {
  +  if (program != null) {
  +    return program.getLocation(fileUri, offset);
  +  } else {
  +    return new Location(fileUri, TreeNode.noOffset, TreeNode.noOffset);
  +  }
  +}
  
positive.code:   }
  
    Location _getLocationInEnclosingFile(int offset) {
      return enclosingProgram.getLocation(fileUri, offset);
    }
  }
  
  
negative.code:   DartType get setterType => isMutable ? type : const BottomType();
  
    Location _getLocationInEnclosingFile(int offset) {
      return _getLocationInProgram(enclosingProgram, fileUri, offset);
    }
  }
  
  