Type families causing the compiler to hang on recompilation

[Jeroen Weijers]

Great, thanks!

I've made a ticket:
http://hackage.haskell.org/trac/ghc/ticket/8002


2013/6/21 Richard Eisenberg <eir at cis.upenn.edu>

> 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.****
>
> ** **
>
> Thanks!****
>
> Richard****
>
> ** **
>
> *From:* glasgow-haskell-users-bounces at haskell.org [mailto:
> glasgow-haskell-users-bounces at haskell.org] *On Behalf Of *Jeroen Weijers
> *Sent:* 21 June 2013 09:01
> *To:* glasgow-haskell-users at haskell.org
> *Subject:* Type families causing the compiler to hang on recompilation****
>
> ** **
>
> Hello,****
>
> ** **
>
> 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.****
>
> ** **
>
> I have tested the problem with GHC (x86_64) 7.6.2. 7.6.3 and HEAD.****
>
> ** **
>
> 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.****
>
> ** **
>
> The code of module A (clutter that doesn't contribute to the problem has
> been removed):****
>
> ** **
>
> > {-# 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 :: *****
>
> ** **
>
> The code of module B:****
>
> ** **
>
> > module B where****
>
> > import qualified A****
>
> ** **
>
> 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. ****
>
> ** **
>
> Does anybody recognise the problem? Should I create a ticket?****
>
> ** **
>
> Cheers,****
>
> ** **
>
> Jeroen Weijers****
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/glasgow-haskell-users/attachments/20130621/02db2d06/attachment.htm>