Should the PVP be changed with regards to instances?

wren ng thornton wren at
Wed Dec 21 18:24:15 CET 2011

On 12/20/11 1:24 PM, Erik Hesselink wrote:
> 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.

Agreed with this. And with Ganesh Sittampalam: the solution to the 
problem of major version changes is automated testing/reporting, not 
allowing potentially breaking changes in minor versions. Yes orphans are 
bad, but they can be required as an interim measure (or, with CPP, for 
backwards compatibility).

Live well,

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