December 2020 - ghc-steering-committee

CUSKs and StandaloneTypeSignatures
by Alejandro Serrano Mena 04 Dec '20

04 Dec '20

Maybe some part of this discussion got lost. Simon PJ writes: Let's *not* have CUSKs. We are trying to get rid of it... it'd be deeply > strange to "bless" it in GHC2020. > > StandaloneKindSignatures is clearly the Right Thing. I'm sure we'll want > it long term. > > It's a very graceful fit with PolyKinds. > I would really like StandaloneTypeSignatures to be part of the default, and remove CUSKs. Thoughts on this? Is it too early? Regards, Alejandro

4 4

#380 GHC2021: What's wrong with Functional dependencies
by Spiwack, Arnaud 04 Dec '20

04 Dec '20

Dear all, It seems that a number of us have voted against including FunctionalDependencies and TypeFamilyDependencies. I don't understand why. They are properly guarded by syntax. I don't know any complaint against them FunctionalDependencies, at least, is as standard as it gets (there are functional dependencies all over the mtl). Is it an oversight? Or do some of us really believe that we ought to keep these out, and why? /Arnaud

4 5

GHC2021: DeriveAnyClass
by Alejandro Serrano Mena 04 Dec '20

04 Dec '20

Dear all, I’ve found as a surprise that several members of the Committee have voted against, or even marked as dangerous, the DeriveAnyClass extension. Given that I am a great fan of it, I would like to open the debate about the particular extension. In my case, most of my uses are to derive ToJSON and FromJSON from the Aeson package. I find it very nice to be able to pack all the information about auto-derived instances in a small block, instead of including Eq and Show in the deriving block, and then a few empty instance declarations below. This is definitely mainly a aesthetic reason. The other reason for adoption is that it makes classes such as Eq or Show less “special”, so one does not have to explain to beginners that some classes can be derived in this way, some others in that other way, and so on. So my other reason for inclusion would be a uniformity one. Regards, Alejandro

5 6