Duplicate instance declarations of a methodless class

[Matthew Brecknell]

Alfonso Acosta:
> Did you try to compile with -fallow-overlapping-instances

mm <schneegloeckchen at gmx.li>:
> Same effect:
> 
> ghc -fallow-overlapping-instances --make test5.lhs
> [1 of 1] Compiling Main             ( test5.lhs, test5.o )
> 
> test5.lhs:22:1:
>     Duplicate instance declarations:
>       instance [overlap ok] (Succ a b) => GT a b
>         -- Defined at test5.lhs:22:1
>       instance [overlap ok] (Succ a b, GT b c) => GT a c
>         -- Defined at test5.lhs:23:1

Also see Oleg's post in this thread:

http://www.haskell.org/pipermail/haskell-cafe/2007-February/022926.html