[ghc-steering-committee] #380 GHC2021: Implications between extensions

Joachim Breitner mail at joachim-breitner.de
Mon Dec 7 20:36:59 UTC 2020


Am Montag, den 07.12.2020, 21:16 +0100 schrieb Alejandro Serrano Mena:
> - What should we do with those which are superseded? I voted ‘yes’ to
> NullaryTypeClasses because it’s implied by MultiParamTypeClasses. I
> don’t think we’ll end up in a situation in which the former is
> accepted but not the latter, but it’s worth mentioning.

my understanding is that implications will hold. So if we vote
MultiParamTypeClasses in, but not NullaryTypeClasses explicitly then 
NullaryTypeClasses would still be active. Just as if you enabled
-XMultiParamTypeClasses. Often, nothing else is technically possible.

In fact, it makes sense to vote
MultiParamTypeClasses: yes
NullaryTypeClasses: no
to express “I want MultiParamTypeClasses, but if that does not make it
in, then NullaryTypeClasses isn't worth going in on its own”.

In general, whatever set we end up with will still be under common
sense scrutiny. 

I have briefly considered digging up the list of implications, and
somehow including it in my updates (“the following extensions would be
enabled by way of implication”). Maybe I’ll do that, we’ll see.


Joachim Breitner
  mail at joachim-breitner.de

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