Re: [Haskell-cafe] Introducing Instances in GHC point releases

duncan.coutts:

What we're currently missing is a PVP checker: a tool to compare APIs of package versions and check that it is following the PVP. Ideally, we will have packages opt-in to follow the PVP for those packages that do opt-in we have the PVP enforced on hackage using the checker tool. Since the HP is almost certainly going to require packages to follow the PVP then this should eliminate this class of mistakes. But it does need the tool, and nobody is working on that at the moment.

If I recall correct, CosmicRay wrote just such a thing (or similar to it) a while ago. John? -- Don