Dimitrios and I don't think there is a fundamental difficulty here, but it involves some work on the constraint solver that we have not yet done, especially concerning the evidence that is constructed for a proof. So it's on the list, but currently not very high priority. Yell if it's important to you. There is a ticket about it: http://hackage.haskell.org/trac/ghc/ticket/4310, so add yourself to the cc list if you care about it. Simon | -----Original Message----- | From: Stefan Holdermans [mailto:stefan@vectorfabrics.com] | Sent: 21 June 2011 10:51 | To: Simon Peyton-Jones; Tom Schrijvers | Cc: glasgow-haskell-users@haskell.org | Subject: Type function under a forall type | | Simon, Tom, | | I hit this type-error message in GHC 7.0.3: | | Cannot deal with a type function under a forall type: | forall e. El e u | | Is there a fundamental reason why type functions under a forall type are a bad idea? | Of is it just something that hasn't been implemented/thought about yet? | | Cheers, | | Stefan