anchor.diff:        Uri uri,
         api.Input<List<int>> dataInput,
         DataSourceIndices importedIndices,
  -      Map<MemberEntity, CodegenResult> results,
  +      Map<MemberEntity, Deferrable<CodegenResult>> results,
         bool useDeferredSourceReads) {
       DataSourceReader source = DataSourceReader(
           BinaryDataSource(dataInput.data, stringInterner: _stringInterner),
  
positive.code:       bool useDeferredSourceReads) async {
      int shards = _options.codegenShards;
      JClosedWorld closedWorld = globalTypeInferenceResults.closedWorld;
      Map<MemberEntity, CodegenResult> results = {};
      for (int shard = 0; shard < shards; shard++) {
        Uri uri = Uri.parse('${_options.readCodegenUri}$shard');
        await measureIoSubtask('deserialize codegen', () async {
  
negative.code:       sink.writeMemberMap(
            results,
            (MemberEntity member, CodegenResult result) =>
                sink.writeDeferrable(() => result.writeToDataSink(sink)));
        sink.close();
      });
    }
  