This will affect snap-core and heist, of the things I've provided
Typeable instances for.
In snap-core, deriving makes it use the internal module name, rather
than the canonical location of the type. This causes issues with the
Hint library, so it's worked around by using a manual instance of
Typeable.
Alternatively, heist involves a monad transformer. "deriving
Typeable" fails for monad transformers, because it can't handle TyCons
with arguments of kind other than *.
So, this change will hit me for two different reasons, and sadly
involve using CPP to control how things are compiled.
Carl
On Mon, Jul 11, 2011 at 11:18 AM, 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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