Great, thanks!
I've made a ticket:
http://hackage.haskell.org/trac/ghc/ticket/8002
2013/6/21 Richard Eisenberg
If the problem is happening in HEAD, it’s a legitimate bug. Please file a report and I’ll take a look at it, as I’m in that area of the codebase right now.****
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Thanks!****
Richard****
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*From:* glasgow-haskell-users-bounces@haskell.org [mailto: glasgow-haskell-users-bounces@haskell.org] *On Behalf Of *Jeroen Weijers *Sent:* 21 June 2013 09:01 *To:* glasgow-haskell-users@haskell.org *Subject:* Type families causing the compiler to hang on recompilation****
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Hello,****
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I am having a problem with (re)compiling some code I have. I have two modules A and B. In A I have some classes and instances and B uses this. When I try to compile B (with cabal or ghc --make) the first time everything works. When I now modify B (add a space) B is recompiled but the compiler hangs and doesn't seems to be doing anything.****
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I have tested the problem with GHC (x86_64) 7.6.2. 7.6.3 and HEAD.****
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It seems to be very similar to a problem I had earlier: http://hackage.haskell.org/trac/ghc/ticket/7321****
but this time there are no GADTs involved.****
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The code of module A (clutter that doesn't contribute to the problem has been removed):****
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{-# LANGUAGE FlexibleInstances, UndecidableInstances #-}****
{-# LANGUAGE GADTs #-}****
{-# LANGUAGE MultiParamTypeClasses #-}****
{-# LANGUAGE TypeFamilies, TypeOperators, ScopedTypeVariables #-}****
{-# LANGUAGE FlexibleContexts #-}****
{-# LANGUAGE DataKinds, PolyKinds #-}****
****
module A where****
****
import GHC.Generics****
****
class QA a where****
type QRep a****
type QRep a = QRep (GRep (Rep a))****
****
instance QA () where****
type QRep () = ()****
****
-- Kind-polymorphic proxies;****
data Pr (a :: k) = Pr****
****
class (QA (GRep f)) => CaseOf (f :: * -> *) where****
type Alg f r k :: *****
type GRep f :: *****
****
-- Only used for the product structure****
class QA (ProdRep f) => CaseOfProd (f :: * -> *) where****
type ProdAlg f r :: *****
type ProdRep f :: *****
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The code of module B:****
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module B where****
import qualified A****
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Given that the code type checks (and if I do not recompile and make an executable directly it actually works) I think this is a bug that might be similar to the bug mentioned in ticket 7321. ****
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Does anybody recognise the problem? Should I create a ticket?****
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Cheers,****
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Jeroen Weijers****