Hello,
I am running into a strange issue that reminds me of Java's classloader black magic havoc :-)

My code compiles fine using cabal-dev install, but when I try to compile an individual file with ghc, I got the following error:

$ ghc -package-conf cabal-dev/packages-7.4.1.conf YakGraph.hs
[1 of 1] Compiling YakGraph         ( YakGraph.hs, YakGraph.o )

YakGraph.hs:13:30:
    Couldn't match expected type `Data.Text.Lazy.Internal.Text'
                with actual type `text-0.11.2.0:Data.Text.Lazy.Internal.Text'
    In the first argument of `unpack', namely `s'
    In the expression: unpack s
    In an equation for `fromGraphId': fromGraphId (Str s) = unpack s

YakGraph.hs:24:57:
    Couldn't match expected type `Data.Text.Lazy.Internal.Text'
                with actual type `text-0.11.2.0:Data.Text.Lazy.Internal.Text'
    In the first argument of `unpack', namely `name'
    In the expression: unpack name
    In a case alternative: (Just (Str name)) : _ -> unpack name

The code leading to this error is here: https://gist.github.com/4677191

Any insights on this would be appreciated.

Arnaud