I suspect that the issue is the following: GHC is inferring a type for a function that could not be written by the user, at least not without -XTypeFamilies or -XGADTs, something like f :: (a ~ F b) => blah blah It's a good principle that if GHC infers a type, then it should be ok to put that type in manually. But that means that you need -XTypeFamilies even for the inferred type. So unless I'm misunderstanding the issue, it's not a bug but a feature. It is a change, certainly, and one that makes GHC a bit more picky. Can you update diagrams to include type signatures or -XGADTs/TypeFamilies? Thanks Simon | -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Gabor | Greif | Sent: 10 June 2014 12:55 | To: ghc-devs | Subject: HEADS-UP: diagrams does not compile with HEAD (regressions) | | Devs, | | as of recently GHC HEAD stopped building the diagrams library. Several | prerequisite libs also fail to compile. A specific error message | appears in an attoparsec issue | https://github.com/bos/attoparsec/issues/67, for which I have | submitted a workaround. But as Herbert cautiously points out, this | could be a recent GHC bug surfacing. | | The symptoms of the bug seem to be that GHC complains about the usage | of (~) type equality operation, but there is no reference to that type | operator in the source code. To work around the problem it suffices to | add -XGADTs or -XTypeFamilies. | | Does this ring any bells? Can automatized tests catch such things in the | future? | | Cheers, | | Gabor | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-devs