[Haskell-beginners] cabal install error: (Illegal instance declaration for `StrictByteString String')

[Brent Yorgey]

It looks like the bytestring-class package has not been updated in a
long time (since 2009) and does not compile under the latest versions
of GHC.

-Brent

On Mon, Jan 21, 2013 at 08:43:17PM +0100, miro wrote:
> Hi, please,....I'm trying to install one package
> (neo4j-haskell-http-client) and below is the error I'm getting. Pls.
> any ideas how can I fix that?
> 
> 
> ---------------
> 
> 1 of 1] Compiling Data.ByteString.Class ( Data/ByteString/Class.hs,
> dist/build/Data/ByteString/Class.o )
> 
> Data/ByteString/Class.hs:39:10:
>     Illegal instance declaration for `StrictByteString String'
>       (All instance types must be of the form (T a1 ... an)
>        where a1 ... an are *distinct type variables*,
>        and each type variable appears at most once in the instance head.
>        Use -XFlexibleInstances if you want to disable this.)
>     In the instance declaration for `StrictByteString String'
> 
> Data/ByteString/Class.hs:55:10:
>     Illegal instance declaration for `LazyByteString String'
>       (All instance types must be of the form (T a1 ... an)
>        where a1 ... an are *distinct type variables*,
>        and each type variable appears at most once in the instance head.
>        Use -XFlexibleInstances if you want to disable this.)
>     In the instance declaration for `LazyByteString String'
> Updating documentation index /Users/miro/Library/Haskell/doc/index.html
> cabal: Error: some packages failed to install:
> bytestring-class-0.0.0 failed during the building phase. The exception was:
> ExitFailure 1
> neo4j-haskell-0.4.1 depends on bytestring-class-0.0.0 which failed to
> install.
> 
> ---------------
> 
> cheers,
> m.

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