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.<p>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.<p>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:C<1337)`; then Excel would flag any rows where the calculation is false (≥1,337).<p>Of course, this kind of goes into treating derived cells as constrained types, but it seems sanity is achieved with the easier checks.<p>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.<p>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 <i>frictive utility</i> with minimal overhead.<p>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."