New implementation for `ImpredicativeTypes`

Alejandro Serrano Mena trupill at
Wed Sep 4 15:13:04 UTC 2019

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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