2016-09-26 9:00 GMT+02:00 Ben Gamari <b...@smart-cactus.org>: > Simon Peyton Jones via ghc-devs <ghc-devs@haskell.org> writes: > > > Friends > > > > GHC has a flag -XImpredicativeTypes that makes a half-hearted attempt > > to support impredicative polymorphism. But it is vestigial.... if it > > works, it's really a fluke. We don't really have a systematic story > > here at all. > > > Out of curiosity, what ever happened to the most recent attempt at > addressing impredicativity [1]? >
It turned our that the new system being proposed was not better than the current one. In particular, it was almost impossible to know upfront whether a program using impredicative types would need an annotation to typecheck. Furthermore, I think it would imply a humongous amount of changes to GHC, for not a very large gain. > > As far as the proposal process is concerned, it would likely be a good > idea to put together a proposal so we have somewhere to collect > comments. That being said, it needn't be terribly lengthy given that we > are merely removing a feature. > > Incidentally, that reminds me that I have some documentation fixes to > the ghc-proposals repository that I should proof-read and push. > > Cheers, > > - Ben > > > [1] https://ghc.haskell.org/trac/ghc/wiki/ImpredicativePolymorphism/ > Impredicative-2015 > > _______________________________________________ > ghc-devs mailing list > ghc-devs@haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs > >
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