anchor.diff:          .toList();
     }
   
  -  Iterable<InboundReference> elements;
  +  Iterable<InboundReference>? elements;
   }
   
   class InboundReference extends Response {
  
positive.code:             break;
            case 'Library':
            case 'LibraryRef':
              final Library library = Library.parse(fieldRef.owner.json);
              owningAllocator = 'Library ${library?.name ?? ""}';
              break;
          }
  
negative.code:     }
  
      // call the build UI callback.
      buildCallback(
        referenceName,
        owningAllocator,
        owningAllocatorIsAbstract,
      );
    }
  }
  
  