I'm thinking a lot of this happens at work where Thrift code generated data structure conversion adapters are commonplace, e.g., from A into B with many fields.

I'm thinking a lot of this happens at work where Thrift code generated data structure conversion adapters are commonplace, e.g., from A into B with many fields. Personally, I think it's the wrong approach and should expose functions that present data as-needed without materializing it wholesale as a different struct because that's expensive, greedy evaluation.