Unknown option -XPatternSig used in warning

[Claus Reinke]

> Via the command line I get the same problem:
> 
> $ ghci -XPatternSigs PatternSig.hs
> GHCi, version 6.7.20070915: http://www.haskell.org/ghc/  :? for help
> ghc-6.7.20070915: unrecognised flags: -XPatternSigs
> Usage: For basic information, try the `--help' option.

    $ /cygdrive/c/fptools/ghc/compiler/stage2/ghc-inplace --supported-languages | grep Pat
    PatternGuards
    PatternSignatures
    BangPatterns
    MonoPatBinds

could it be that the error message is incorrect, pointing
to an abbreviated form?

>   Illegal signature in pattern: a
>    Use -XPatternSigs to permit it

claus