[hvr_]

> Would it be possible to do this more like GNU configure does? The software specifies what it needs, and the system looks for a version that works. How about check the Haskell code automatically to see what functions it uses?

This gets often suggested every time the version bounds topic comes up (to some degree, that's the direction backpack is going btw). But unfortunately this does not work:

Because what this argument ignores is that you get a similar problem you have with duck-typing on a different level: You assume that the same name & type-signature provides the same semantics. However, the types usually leave too much degree of freedom to provide a proper contract. And you have to find a way to encode that contract.

The best-bang-for-buck way we currently have to encode this contract is... well... the PVP! Version numbers announce the contract, while version bounds define which contract you rely on.

Unless we have a better way to solve this, there's no alternative to the PVP. Unfortunately, so far I have not heard any workable solution from PVP complainers. So that's that.