On Wednesday 29 June 2011, 11:37:39, Yitzchak Gale wrote:
>
> So it's the derived Read instance in this context that
> is causing the problem. Here is a slightly smaller test
> case that triggers the bug:
>
> {-# LANGUAGE MultiParamTypeClasses, UndecidableInstances #-}
> module Bug where
> class
Daniel Fischer wrote:
> No, the instance head is just a type variable, not a type constructor
> applied to type variables
Oops, you're right. GHC was telling the truth, I should have
paid closer attention!
Fixing my minimal example, I get:
{-# LANGUAGE MultiParamTypeClasses, UndecidableInstances
On Wednesday 29 June 2011, 10:22:20, Yitzchak Gale wrote:
> Ryan Ingram wrote:
> > So this is definitely a GHC bug, but I think the problem is probably
> > triggered by this line:
> >
> > instance Serializable a b => IResource a
> >
> > I don't think this is a valid instance declaration without
http://hackage.haskell.org/trac/ghc/ticket/5287
El 29/06/2011 10:22, "Yitzchak Gale" escribió:
> Ryan Ingram wrote:
>> So this is definitely a GHC bug, but I think the problem is probably
>> triggered by this line:
>>
>> instance Serializable a b => IResource a
>>
>> I don't think this is a valid
Ryan Ingram wrote:
> So this is definitely a GHC bug, but I think the problem is probably
> triggered by this line:
>
> instance Serializable a b => IResource a
>
> I don't think this is a valid instance declaration without a functional
> dependency on Serializable, as it's impossible to know whic
Ryan'
P robably the read instance can not be infered without the functional
dependency but the bug is also triggered with it. I simplified ithe coder as
much as possible
El 29/06/2011 02:26, "Ryan Ingram" escribió:
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So this is definitely a GHC bug, but I think the problem is probably
triggered by this line:
instance Serializable a b => IResource a
I don't think this is a valid instance declaration without a functional
dependency on Serializable, as it's impossible to know which type 'b' to use
in the method
Reported:
http://hackage.haskell.org/trac/ghc/ticket/5287
2011/6/28 Alberto G. Corona
>
> 2011/6/28 Jason Dagit
>
>> On Tue, Jun 28, 2011 at 3:43 AM, Alberto G. Corona
>> wrote:
>> > I have an "'impossible' happened" error.
>> > The code may look a little bit convoluted but it is part of my re
On Tue, Jun 28, 2011 at 3:43 AM, Alberto G. Corona wrote:
> I have an "'impossible' happened" error.
> The code may look a little bit convoluted but it is part of my real code.:
I don't know why it's crashing, but did you already report it as a
bug? If not, you definitely should.
> Please repor
I have an "'impossible' happened" error.
The code may look a little bit convoluted but it is part of my real code.:
- begin of code--
{-# LANGUAGE FlexibleInstances, UndecidableInstances
, MultiParamTypeClasses
#-}
class Serializable a b
class IRe
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