[Haskell-cafe] Re: Cabal Compiler Flag Problem

[Anders Kaseorg]

On Wed, 24 Mar 2010, Ben Derrett wrote:
> Control/Monad/CatchIO.hs:146:34:
>     Illegal signature in pattern: E.SomeException
>         Use -XPatternSignatures to permit it

A fix is to avoid using a pattern signature in Control/Monad/CatchIO.hs:

-onException a onEx = a `catch` (\(e::E.SomeException) -> onEx >> throw e)
+onException a onEx = a `catch` \e -> onEx >> throw (e :: E.SomeException)

I reported this to the MonadCatchIO-mtl maintainer a few days ago; 
hopefully it will be fixed soon.  (I’ve CCed him as a reminder.)

Meanwhile, you can use cgi-3001.1.7.3, which does not require 
MonadCatchIO-mtl.

Anders