[Haskell-cafe] Introducing Instances in GHC point releases

[John Goerzen]

Henning Thielemann wrote:
> John Goerzen schrieb:
>> So this is annoying (CCing -cafe)
>>
>> I need NominalDiffTime and UTCTime to have Typeable instances.  In
>> 6.10.1, they didn't ship with them out of the box, so I added them.
>> Apparently, in 6.10.3, they DO ship with those instances out of the box.
>>
>> Annoyingly, that means that my code breaks on 6.10.3.
> 
> After having conflicting instances several times with some types in the
> past, I came to the conclusion that I should never define orphan
> instances. Can you restrict your package to 6.10.3 where an "official"
> instance is available?
> 
> http://www.haskell.org/haskellwiki/Orphan_instance
> 

I didn't care about presenting the instance to people using my library,
but the instance was necessary within the library itself, and led to the
compilation error.

-- John