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