Fixing type synonyms to Uniq(D)FM newtypes

Andreas Klebinger klebinger.andreas at
Tue Jun 23 23:08:55 UTC 2020

My main motivation for going with a phantom type over newtypes was that
it makes it easier to use in
an adhoc fashion without giving up type safety.

As a second benefit it seemed a lot easier to implement.


George Colpitts schrieb am 24.06.2020 um 00:40:
> I read the email thread you refer to but it doesn't seem to explain
> why you went with solution 2. If you think it worthwhile can you
> explain here why you chose solution 2?
> On Tue, Jun 23, 2020 at 6:55 PM Andreas Klebinger
> <klebinger.andreas at <mailto:klebinger.andreas at>> wrote:
>     There was a discussion about making UniqFM typed for the keys here a
>     while ago.
>     (
>     and following)
>     I wrote up an MR for one possible approach here:
>     It implements solution 2 from that discussion.
>     Just while getting the patch to typecheck I've already seen a
>     number of
>     cases where this increased
>     readability of the code quite a bit so I think it's a good
>     improvement.
>     If there are strong objections to this solution let me know. In that
>     case I'm happy to abandon the patch.
>     If not I will clean it up and get it ready for merging.
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>     ghc-devs mailing list
>     ghc-devs at <mailto:ghc-devs at>

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