Should the PVP be changed with regards to instances?

Erik Hesselink hesselink at
Tue Dec 20 19:24:06 CET 2011

I'd ask you to follow the PVP here. Problems with duplicate instances
are often tricky to resolve, and not something you want to encounter
when you're developing (not upgrading dependencies). I've often added
orphan instances for types from other packages. Yes, I should (and
often do) send these upstream, but I still add them locally. I have to
have the instance now, to continue my work, and there's no telling
when a new version of the original package will be released. The other
option is forking the package, which means I also don't get bugfix
updates anymore.

So in short: I find breakage due to conflicting instances much more
annoying than a major version bump.


On Tue, Dec 20, 2011 at 17:12, Johan Tibell <johan.tibell at> wrote:
> Hi,
> I find myself reluctant to add new instances to the unordered-containers
> package, because doing so would require a major version bump according to
> the PVP. Major version bumps are annoying for several reasons:
>  * Libraries that depend on unordered-containers need to be updated and make
> new releases.
>  * We get rapid successions of major releases without many actual changes
> (i.e. none as far as most users are concerned).
> Introducing new instances is unlikely to break users, as they will only get
> into trouble if they use orphan instances, which is already asking for
> trouble!
> Thoughts?
> Cheers,
> Johan
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