Thanks Richard. Basically I was storing the type family and its arguments in the data type, so that I can transform its arguments before it gets applied to stored typefamily (via. another closed type function). Is this even possible to do by any chance in 7.8.4 & later?
On Tue, Jan 13, 2015 at 8:32 PM, Richard Eisenberg <e...@cis.upenn.edu> wrote: > Hello Magesh, > > The bug is in 7.8.3, which should never have allowed your `Test1`. Haskell > type families may not be partially applied -- the type system and type > inference just don't know how to handle such things. In 7.8.3, the check > was accidentally turned off, as discussed in #9433, as you found. 7.8.3 > allows you to do a few limited things with partially applied families, but > you'll get very strange errors if you continue down that road, as GHC > quickly gets horribly confused. > > I'm afraid you'll have to find a different way to express what you want. > > Richard > > On Jan 13, 2015, at 9:49 AM, magesh b <mages...@gmail.com> wrote: > > Hi, > > {-# LANGUAGE TypeFamilies, ConstraintKinds #-} > > import GHC.Exts > > type family TyFun a > > data DictC (c :: * -> Constraint) > > data DictTF (tf :: * -> *) > > type Test1 = DictTF TyFun -- Fails here in 7.8.4 > > type Test2 = DictC Show > > When I compile the above code, I'm getting the following error in 7.8.4 > and the same code works in 7.8.3. > > Test.hs:11:1: > Type synonym ‘TyFun’ should have 1 argument, but has been given none > In the type declaration for ‘Test1’ > > Is this a bug or a expected behavior? > For reference, I could find two fixes to type family related bug in this > release. > https://ghc.haskell.org/trac/ghc/ticket/9433 > https://ghc.haskell.org/trac/ghc/ticket/9316 > > > Thanks & Regards, > Magesh B > > > _______________________________________________ > ghc-devs mailing list > ghc-devs@haskell.org > http://www.haskell.org/mailman/listinfo/ghc-devs > > >
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