[Haskell-cafe] The weirdest error I've ever seen...
jfredett at gmail.com
Thu Nov 12 13:12:03 EST 2009
Actually, I just solved the problem... I think...
In my original code, I had the newtype:
newtype FilterState t => Filter t a = Filter (ContextMatch t a)
deriving (Functor, Monad, MonadReader Email, MonadState Bool,
I was trying to confirm that it actually was the `deriving ...
MonadState Bool ...` part that was causing the problem, and then I
realized, it's not `MonadState Bool` I want, it's `MonadState t`.
Upon changing that, everything compiles fine and ghc hums along happily.
Should I still submit a bug report for a bad error message?
On Nov 12, 2009, at 12:58 PM, Joe Fredette wrote:
> Okay, so -- I feel totally awesome -- I never found a GHC bug
> before... and a Haskell Celebrity responded to my post! *swoons* :)
> Serious question now, There's a fair amount of definitely irrelevant
> code (like the definition of the `Email` type, etc), should I post
> that in the report too (assuming it doesn't work in 6.12 or I can't
> get 6.12 working to try it)?
> On Nov 12, 2009, at 4:07 AM, Simon Peyton-Jones wrote:
>> | [1 of 3] Compiling Network.HackMail.Email.ParseEmail ( Network/
>> | HackMail/Email/ParseEmail.hs, interpreted )
>> | [2 of 3] Compiling Network.HackMail.Email.Email ( Network/HackMail/
>> | Email/Email.hs, interpreted )
>> | [3 of 3] Compiling Network.HackMail.Filter.Filter ( Network/
>> | Filter/Filter.hs, interpreted )
>> | *** Exception: No match in record selector Var.tcTyVarDetails
>> This is a bug in GHC without a doubt.
>> It's possible that it's fixed in 6.12 -- can you try the release
>> candidate? If it is not fixed, or if it's too hard for you to try,
>> can you submit a Trac bug report please? (Include your code, and
>> instructions for how to reproduce.
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