New implementation for `ImpredicativeTypes`

Simon Peyton Jones simonpj at
Thu Sep 5 10:23:24 UTC 2019

I update the MR Description<> to make the link more discoverable.


From: ghc-devs <ghc-devs-bounces at> On Behalf Of Alejandro Serrano Mena
Sent: 05 September 2019 09:30
To: GHC developers <ghc-devs at>
Subject: Re: New implementation for `ImpredicativeTypes`

To follow up on this, the current spec. is available in the following PDF:<>

El mié., 4 sept. 2019 a las 17:13, Alejandro Serrano Mena (<trupill at<mailto:trupill at>>) escribió:
Hi all,
As I mentioned some time ago, we have been busy working on a new implementation of `ImpredicativeTypes` for GHC. I am very thankful to everybody who back then sent us examples of impredicativity which would be nice to support, as far as we know this branch supports all of them! :)

If you want to try it, at<> you can find the result of the pipeline, which includes builds for several platforms (click on the "Artifacts" button, the one which looks like a cloud, to get them). The code is being developed at<>.

Any code should run *unchanged* except for some eta-expansion required for some specific usage patterns of higher-rank types. Please don't hesitate to ask any questions or clarifications about it. A merge request for tracking this can be found at<>

Kind regards,
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