anchor.diff:        new Uri(scheme: "org-dartlang-debug", path: "synthetic_debug_expression");
   
     KernelTarget userCode;
  +  Set<Library> previousSourceBuilders;
   
     IncrementalCompiler.fromComponent(
         this.context, this.componentToInitializeFrom,
  
positive.code:       await dillLoadedData.buildOutlines();
      }
      if (userBuilders.isEmpty) userBuilders = null;
    }
  
    /// Compute which libraries to output and which (previous) errors/warnings we
  
negative.code:     if (userCode != null) {
        Set<Uri> uris = new Set<Uri>.from(userCode.loader.builders.keys);
        uris.removeAll(dillLoadedData.loader.builders.keys);
        if (previousSourceBuilders != null) {
          for(Library library in previousSourceBuilders) {
            uris.add(library.importUri);
          }
        }
        invalidatedUris.addAll(uris);
      }
    }
  