Getting rid of -XImpredicativeTypes

Ben Gamari ben at
Mon Sep 26 07:00:16 UTC 2016

Simon Peyton Jones via ghc-devs <ghc-devs at> 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]?

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.


- Ben

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