Alberto G. Corona
What to do when the data has been defined in other package and provides no Typeable instance?
You'd have to use standalone deriving, which I hope gets into Haskell 201X. ---- module A where data A = A ---- {-# LANGUAGE StandaloneDeriving, DeriveDataTypeable #-} module B where import A import Data.Typeable deriving instance Typeable A ---- Cheers, Thomas
2011/7/11 Yitzchak Gale
Simon Marlow has announced[1] on the Haskell Libraries list that the Typeable class is changing.
The standard way to create a Typeable instance is just to derive it. If you do that, you will not be affected by this change.
But it seems that many packages create Typeable instances by explicitly using mkTyCon. If your package does this, it will eventually break, after a deprecation period.
Please respond to this thread if you own a package that will be affected by this change.
Can someone who has quick access to the entire contents of Hackage please do a grep and find out exactly which packages on Hackage will be affected? Thanks.
-Yitz
[1] http://www.haskell.org/pipermail/libraries/2011-July/016546.html
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