Ah. Good point. I've made a simplified test case https://ghc.haskell.org/trac/ghc/ticket/8565 Thanks Simon | -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of Kazu | Yamamoto | Sent: 26 November 2013 02:45 | To: ghc-devs@haskell.org | Subject: Cannot instantiate unification variable | | Hi, | | Recent GHC head on 32bit Linux cannot build conduit-1.0.9.2. (See the | attached log.) A while ago, GHC head on 32bit Linux could build it. | The same GHC head on 64bit Linux can build it. | | Michael Snoyman suggested me to add ImpredicativeTypes. When I added | it to the Internal.hs, GHC head on 32bit Linux can build it. And he | said to other released GHCs can build it. Actually, GHC 7.4.2 on | 32bit Linux can build it. | | He believes that this is a bug of GHC head (on 32bit Linux). Any | information? | | Note that conduit-1.0.9.3 already includes ImpredicativeTypes. | | --Kazu | | Building conduit-1.0.9.2... | Preprocessing library conduit-1.0.9.2... | [2 of 8] Compiling Data.Conduit.Internal ( Data/Conduit/Internal.hs, | dist/build/Dat | a/Conduit/Internal.o ) | | Data/Conduit/Internal.hs:211:105: | Cannot instantiate unification variable ‛b0’ | with a type involving foralls: | (forall a. m1 a -> n1 a) | -> ConduitM i o m1 b1 -> ConduitM i o n1 b1 | Perhaps you want ImpredicativeTypes | In the expression: | GHC.Exts.coerce | (hoist :: | (forall (a :: *). m a -> n a) | -> Pipe i i o () m b -> Pipe i i o () n b) :: | forall (m :: * -> *) (b :: *) (n :: * -> *). Monad m => | (forall (a :: *). m a -> n a) | -> ConduitM i o m b -> ConduitM i o n b | In an equation for ‛hoist’: | hoist | = GHC.Exts.coerce | (hoist :: | (forall (a :: *). m a -> n a) | -> Pipe i i o () m b -> Pipe i i o () n b) :: | forall (m :: * -> *) (b :: *) (n :: * -> *). Monad m => | (forall (a :: *). m a -> n a) | -> ConduitM i o m b -> ConduitM i o n b | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-devs