anchor.diff:        }
       }
       this._imports = imports;
  +    this._prefixes = null;
     }
   
     @override
  
positive.code:    * A bit-encoded form of the capabilities associated with this library.
     */
    int _resolutionCapabilities = 0;
  
    /**
     * Initialize a newly created library element in the given [context] to have
  
negative.code: 
    PrefixElement get prefix {
      if (_unlinkedImport != null) {
        if (_unlinkedImport.prefixReference != 0 && _prefix == null) {
          LibraryElementImpl library = enclosingElement as LibraryElementImpl;
          _prefix = new PrefixElementImpl.forSerialized(_unlinkedImport, library);
        }
  