The thing I learned from the incident is that rust offer a unpack function. It puzzles me why the hell they build such a function in the first place.

> It puzzles me why the hell they build such a function in the first place.

One reason is similar to why most programming languages don't return an Option<T> when indexing into an array/vector/list/etc. There are always tradeoffs to make, especially when your strangeness budget is going to other things.