[Haskell-cafe] Pattern synonyms and explicit forall.

coot at coot.me coot at coot.me
Sat Sep 18 14:32:04 UTC 2021

On Saturday, September 18th, 2021 at 14:12, Anthony Clayden <anthony.d.clayden at gmail.com> wrote:

> The end of your error message:

> >       |
> >    63 | pattern Any a <- Some a
> >       |                       ^ 


> Appears to have program text (a mono-directional pattern binding) that doesn't correspond to the program text you quote.

I just tried both ways of writing bidirectional pattern synonmys, neither worked with explicit `forall`.

> I'm suspecting the explicit forall is not much to do with it.

With an implicit forall, the code does type check.


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