On 9 Dec 2020 at 14:40:13, Joachim Breitner
Hi,
Am Mittwoch, den 09.12.2020, 12:08 +0000 schrieb Simon Peyton Jones via ghc-steering-committee:
I agree with this. Not having scoped type variables (in any form) is
a huge blemish. The existing design may not be perfect, but it’s
worked rather well for a long time.
The same is true for ViewPatterns, which are even more harmless (clear syntactic opt-in; no spooky effect at a distance when type signature and definition are far apart).
There we argued that the fact that we don’t think it’s perfect, and some wiki page with an alternative design exists, was enough to plea against it.
Here, the situation seems equivalent (we know of better designs, namely binding type variables on the LHS of the equation).
Can we justify why we go one way here and another way there? Is it because ViewPatterns are just mere convenience, and ScopedTypeVariables are absolutely needed for some things?
This is what I think at least (I also voted ‘yes’ for ViewPatterns, but I wouldn’t mind not having them). No ViewPatterns, I just need one extra ‘case’ to stay in GHC2021. Alejandro