anchor.diff:        packageInfoNodes[packageName] = newPackage;
         program.root.children[packageName] = newPackage;
         outputInfo.add(newPackage);
  +      var packageNode = infoNodesByName[newPackage.name];
  +      assert(packageNode == null, "encountered package with duplicated name");
         infoNodesByName[newPackage.name] = newPackage;
       } else {
         packageInfoNode.size = (packageInfoNode.size ?? 0) + libraryInfo.size;
  
positive.code:           type: vm.NodeType.classNode);
        newClass.size = classInfo.size;
        parentNode.children[newClass.name] = newClass;
        infoNodesByName[newClass.name] = newClass;
        outputInfo.add(newClass);
      }
  
negative.code:           type: vm.NodeType.functionNode);
        newFunction.size = functionInfo.size;
        parentNode.children[newFunction.name] = newFunction;
        vm.ProgramInfoNode? functionNode = infoNodesByName[newFunction.name];
        assert(functionNode == null, "encountered function with duplicated name");
        infoNodesByName[newFunction.name] = newFunction;
        outputInfo.add(newFunction);
      }
  