dgorin:
> I've tried adding some signatures (together with -
> XScopedTypeVariables), but with no luck. Why is it that this no longer
> compiles? More importantly, how can I make it compile again? :)
>
If you work out how to make it compile, can you document the soln. here,
http://haskell
On Oct 14, 2008, at 7:48 PM, Don Stewart wrote:
dgorin:
I've tried adding some signatures (together with -
XScopedTypeVariables), but with no luck. Why is it that this no
longer
compiles? More importantly, how can I make it compile again? :)
If you work out how to make it compile, can you
On Tue, Oct 14, 2008 at 7:27 AM, Daniel Gorín <[EMAIL PROTECTED]> wrote:
> Hi
>
> After installing ghc 6.10-rc, I have a program that no longer compiles. I
> get the dreaded "GADT pattern match" error, instead :)
>
> Here is a boiled-down example:
>
> {-# OPTIONS_GHC -XGADTs -XEmptyDataDecls #
On Oct 14, 2008, at 10:19 PM, Jason Dagit wrote:
On Tue, Oct 14, 2008 at 7:27 AM, Daniel Gorín <[EMAIL PROTECTED]>
wrote:
Hi
After installing ghc 6.10-rc, I have a program that no longer
compiles. I get the dreaded "GADT pattern match" error, instead :)
Here is a boiled-down example
On Tue, Oct 14, 2008 at 6:37 PM, Daniel Gorín <[EMAIL PROTECTED]> wrote:
>
> On Oct 14, 2008, at 10:19 PM, Jason Dagit wrote:
>
>
> On Tue, Oct 14, 2008 at 7:27 AM, Daniel Gorín <[EMAIL PROTECTED]> wrote:
>
>> Hi
>>
>> After installing ghc 6.10-rc, I have a program that no longer compiles. I
>> ge
| After installing ghc 6.10-rc, I have a program that
| no longer compiles. I get the dreaded "GADT pattern match"
| error, instead :)
I'm sorry it's dreaded! Jason is right that the key point is this:
GHC now enforces the rule that in a GADT pattern match
- the type of the scrutinee
Hi, Simon
Thanks a lot for your mail. It turns out I could have resolved this by
myself (with the help of this thread http://thread.gmane.org/gmane.comp.lang.haskell.glasgow.user/15153
, to be honest). What I was missing was this key part:
bind :: forall a b t. W t a -> (a -> W t b) -> W_ t
| > In your case the error message was:
| >
| > GADT.hs:26:56:
| >GADT pattern match with non-rigid result type `Maybe a'
| > Solution: add a type signature
| >In a case alternative: I1 m' -> m'
| >In the expression: case w' S of { I1 m' -> m' }
| >In a case alternative: Wrap w
