-fallow-incoherent-instances

[Christian Maeder]

I wrote:
> If, furthermore, the "confusing instance" is commented out, the source 
> even compiles without extensions.

Correction: -fglasgow-exts is still required for the type 
GeneralBreakFn, but -fallow-overlapping-instances can be omitted.

> {-# OPTIONS -fglasgow-exts -fallow-overlapping-instances -fallow-undecidable-instances -fallow-incoherent-instances #-}
> module InCoherentInst where
> 
> import Control.Exception(throwDyn)
> 
> import Data.Typeable(Typeable)
> 
> class Confuse a where
>     confuse :: a -> String
> 
> instance Confuse a => Typeable a
> 
> data GeneralBreakFn a = GeneralBreakFn (forall b . a -> b)
> 
> addGeneralFallOut :: Typeable a => GeneralBreakFn a
> addGeneralFallOut =
>       let breakFn a = throwDyn (GeneralFallOutExcep a)
>       in GeneralBreakFn breakFn
> 
> data GeneralFallOutExcep a = GeneralFallOutExcep a deriving (Typeable)