Re: [Haskell-cafe] TypeApplications and Proxy

I would say that TypeApplications is stable enough, and that the ordering of type variables is reliable enough. But, sadly, we can't quite get rid of Proxy yet. Here's a very contrived example: type family F a hr :: (forall a. F a -> ()) -> () hr _ = () x = hr (\ _ -> ()) In the body of the lambda there, it is impossible to bind the type variable `a` with any Haskell construct. The workaround is to use Proxy in the type of hr. I don't know another way to do it. So I'm all for removing other uses of Proxy, but I don't think we should quite drop it from base, yet. Proposal #155 (https://github.com/ghc-proposals/ghc-proposals/pull/155) is in this area, but it's not yet implemented. Richard

On Sep 14, 2020, at 3:34 PM, Johannes Waldmann wrote:

...

TypeApplication depends on the order in which type variables are introduced.

https://downloads.haskell.org/ghc/latest/docs/html/users_guide/glasgow_exts....

The easy fix is to declare all type variables. Then the first clause of 9.19.2 is enough?

- J. _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.