With the patch for #2161 applied I get this with ghc 6.12.1 and the
current screened repo:

[106 of 180] Compiling Darcs.Patch.V2.Real ( src/Darcs/Patch/V2/Real.hs, dist/build/Darcs/Patch/V2/Real.o )

src/Darcs/Patch/V2/Real.hs:134:18:
    GADT pattern match in non-rigid context for `Etacilpud'
      Probable solution: add a type signature for `isForward''
    In the pattern: Etacilpud _
    In the definition of `isForward'':
        isForward' (p@(Etacilpud _)) = justRedP "An inverse duplicate" p
    In the definition of `isForward':
        isForward = isForward'
                  where
                      isForward' (p@(InvConflictor _ _ _))
                                   = justRedP "An inverse conflictor" p
                      isForward' (p@(Etacilpud _)) = justRedP "An
    inverse duplicate" p
                      isForward' _ = Nothing
                      justRedP msg p = Just $ redText msg $$ showPatch p

due to

Wed Mar 21 21:36:32 GMT 2012  Owen Stephens <darcs@owenstephens.co.uk>
  * Style, tidy and start commenting Real.hs

Hi fx,

I've sent a patch that (I hope) fixes this: http://bugs.darcs.net/patch764

Could you give it a try?
Thanks,
Owen.

Owen Stephens <bugs@darcs.net> writes:

> Owen Stephens <darcs@owenstephens.co.uk> added the comment:
>
> Hi fx,
>
> I've sent a patch that (I hope) fixes this: http://bugs.darcs.net/patch764
>
> Could you give it a try?

It builds with that on top of the previous patch, thanks.

The following patch sent by Owen Stephens <darcs@owenstephens.co.uk> updated issue issue2162 with
status=has-patch

* Resolve issue2162 
Ignore-this: 8af0d7865e9e68fe182516351bf0b845

The following patch sent by Owen Stephens <darcs@owenstephens.co.uk> updated issue issue2162 with
status=resolved;resolvedin=2.8.0 HEAD

* Resolve issue2162 
Ignore-this: 8af0d7865e9e68fe182516351bf0b845

This is now really resolved in the 2.8 branch (the patch tracker was for a 
while erroneously reporting things pushed to HEAD as being fixed in 2.8, 
which is why it was already listed that way)