Excel will allow certain auto data conversions to be turned off
It would be nice if Excel had a builtin "double bookkeeping" feature: given a formula, ensure results are also calculated or accounted for in another place.It would be cumbersome to always have it enabled, so it could certainly be disabled by default. But Microsoft could market the feature with suggestive tooltips.One example is if I have the fornula `=A1+B1` in cell C1, I can go to a separate worksheet and generate a constraint like `=MUST(W1!C:COf course, this kind of goes into treating derived cells as constrained types, but it seems sanity is achieved with the easier checks.Constraints or properties are nice in that they are not unit tests; they could be added at the "moment of instantiation" like an object constructor--but in this case, the violation occurs as a post hoc check. It has to happen first.You might say, "I always triple-check my models and ensure worksheets are equal in multiple ways." Maybe it's possible to do it already. Sometimes, quality is about introducing frictive utility with minimal overhead.The problems solved are usually not handled with only with an integer primitive, but hand in hand with a domain component that makes us pause and go, "Okay, I guess a person's age won't be MAX_VALUE or negative."