anchor.diff:  
       _byteOffset = index.binaryOffsetForSourceTable;
       Map<Uri, Source> uriToSource = readUriToSource();
  -    component.uriToSource.addAll(uriToSource);
  +    _mergeUriToSource(component.uriToSource, uriToSource);
   
       _byteOffset = _componentStartOffset + componentFileSize;
     }
  
positive.code:       readUint32();
      }
      return uriToSource;
    }
  
    CanonicalName readCanonicalNameReference() {
  
negative.code: 
      _byteOffset = index.binaryOffsetForSourceTable;
      Map<Uri, Source> uriToSource = readUriToSource();
      _mergeUriToSource(component.uriToSource, uriToSource);
  
      _byteOffset = index.binaryOffsetForConstantTable;
      readConstantTable();
  